http://www.javabeat.net/rss/jb-tips.xml JavaBeat Tips en-us My copyright text 2009-03-30T17:48:58+01:00 me my subject http://www.javabeat.net/tips/189-gwt-user-interface-components.html A GWT module needs a HTML host page to run. The HTML page includes the GWT project through the script tag. In the HTML page we do not add any HTML code ourselves. It is the responsibility of the developer to programmatically include content into the HTML page through GWT. Lets look at a sample HTML host page : http://www.javabeat.net/tips/189-gwt-user-interface-components.html http://www.javabeat.net/tips/188-gwt-installation-and-creating-a-gwt-project.html To develop programs using the GWT we need to first download it from here : GWT download. Once you have it installed the next step would be to update the PATH environmental variable. For example if you have installed GWT in you C: drive as C:\gwt-windows-1.5.3 then append this path to the end of the PATH variable. Once this is done you are ready to create GWT projects. http://www.javabeat.net/tips/188-gwt-installation-and-creating-a-gwt-project.html http://www.javabeat.net/tips/187-xml-schema-elements-part2.html Complex elements are those which contain other elements as children or these elements have attributes. Empty elements and elements containing only text are also considered complex. The following is an examples of complex element http://www.javabeat.net/tips/187-xml-schema-elements-part2.html http://www.javabeat.net/tips/186-xml-schema-elements.html XML schema is a language for describing the contents and structure of a XML document. It basically creates a blue print of the actual XML document by describing everything about the elements which can appear in the document. By creating a XML schema we make the XML document conform to the rules defined in the XML schema. It essentially says that the XML document cant break the rules defined in the XML schema document. http://www.javabeat.net/tips/186-xml-schema-elements.html http://www.javabeat.net/tips/185-xforms.html Forms in HTML are used to group other HTML controls together. A user basically interacts with a system through these input controls placed inside a form. http://www.javabeat.net/tips/185-xforms.html http://www.javabeat.net/tips/184-creating-xslt-documents.html XSLT is used for the transformation of XML documents into XHTML. We know that HTML uses predefined set of tags which can be interpreted by the browser. However this is not true for XML documents. XML does not use predefined set of tags. Hence, if we open an XML document in browser we cant expect the browser to display the document in some meaningful format. http://www.javabeat.net/tips/184-creating-xslt-documents.html http://www.javabeat.net/tips/183-how-to-use-xlink-and-xpointer.html In HTML we use anchor tags to create hyperlinks. On the same lines we can create hyperlinks in an XML document using XLink. With XLink we can define two types of link : simple and extended. Simple links are links similar to HTML links and extended links are used for linking multiple resources together. http://www.javabeat.net/tips/183-how-to-use-xlink-and-xpointer.html http://www.javabeat.net/tips/182-how-to-query-xml-using-xpath.html XML Documents are nothing until some kind of Components called Parsers parses the Documents to extract the meaningful data. Some of the most popular XML Parsers are the Simple API for XML (SAX) and Document Object Model (DOM). Both these parsers have their own advantages and disadvantages in parsing the XML Documents. XPath is a simple Query Language for querying data from a XML Document and it is a standard specification from the W3C Group. http://www.javabeat.net/tips/182-how-to-query-xml-using-xpath.html http://www.javabeat.net/tips/181-xquery-syntax.html XQuery is a concept very similar to SQL. As sql is used to query database tables we can use XQuery to query XML data. Xquery can be used to query XML documents, data which is in XML syntax and databases. Using XQuery we can find XML elements. This can be very useful in situations when we need to search relevant information in large XML documents or XML data. http://www.javabeat.net/tips/181-xquery-syntax.html http://www.javabeat.net/tips/180-jstl-function-in-jsp-20.html In JSP 2.0 we can perform string operations in JSP without using any java code inside scriptlets. This is possible with the latest release of JSTL 1.1. The new library called Functions with prefix as fn allows us to perform string operations in JSP 2.0. http://www.javabeat.net/tips/180-jstl-function-in-jsp-20.html http://www.javabeat.net/tips/179-dynamic-attributes-in-tag-file-in-jsp-20.html As we know that we can develop custom tag library as a simple tag file in JSP 2.0 and these tag files can accept attributes from the invoking JSP page. But one drawback of this approach is that we need to declare all the attributes in the tag file. JSP 2.0 provides a feature called dynamic attributes by using which we need not declare the attributes in the tag file using the attribute directive. http://www.javabeat.net/tips/179-dynamic-attributes-in-tag-file-in-jsp-20.html http://www.javabeat.net/tips/178-servletcontextlistener-example.html This tips explains the how to use ServletContextListener. There will be only one ServletContext for each web application. ServletContext will be created while deploying the application. Once the ServletContext is created, it will be used by all the servlets and jsp files in the same application. ServletContext is also called as the application scope variables in the web application scenario. http://www.javabeat.net/tips/178-servletcontextlistener-example.html http://www.javabeat.net/tips/177-variable-directive-in-jsp-20-custom-tags.html This tips explains how to use the variable directive in the custom tags in JSP 2.0. There is time when JSP page needs to access the variable declared inside the Tag files. In the previous version we have to extend the tag library to declare the variables and need the special handling for those variables. In JSP 2.0, it is done very easily using the variable directive. Syntax for the variable directive is as follows: http://www.javabeat.net/tips/177-variable-directive-in-jsp-20-custom-tags.html http://www.javabeat.net/tips/176-custom-tags-in-jsp-20.html Developing custom tags in the previous JSP versions are tedious and it is considered as one of the complex task for the JSP developers. Because inorderto write a simple custom tag you have to learn many things and should have good knowledge on Java also. Apart from that you have to use Tag APIs to create a complete tag library. Any small mistake will cause the error and tag files will not work. To make the things easy for the JSP developers, JSP 2.0 has the advanced features for creating JSP custom tag libraries. http://www.javabeat.net/tips/176-custom-tags-in-jsp-20.html http://www.javabeat.net/tips/175-custom-tag-libraries-and-tag-files-in-jsp-20.html With previous versions of JSP developing custom tag libraries was possible only by writing Java classes. As a result knowledge of Java was a must. JSP 2.0 introduces a new way of developing custom tag library using plain JSP. This enables JSP developers, who dont know Java, to develop custom tag libraries as Tag files. JSP 2.0 also provided added features of passing parameters to tag files. I will demonstrate this in the following examples. http://www.javabeat.net/tips/175-custom-tag-libraries-and-tag-files-in-jsp-20.html http://www.javabeat.net/tips/174-error-pages-in-jsp-20.html We can configure error pages in jsp and servlets to direct the control to a custom error page, showing a friendly error message to the user when an exception is thrown in the page. But tracking or logging the exception information is not very easy in JSP 1.2. JSP 2.0 fixes this problem by switching to the servlet specification: javax.servlet.error.exception. In addition, a new property of the implicit EL pageContext variable, named errorData, exposes other information about the problem. The errorData property is an instance of the javax.servlet.jsp.ErrorData class that can be used as a bean with the following properties: http://www.javabeat.net/tips/174-error-pages-in-jsp-20.html http://www.javabeat.net/tips/173-ternary-operator-in-jsp-20-expression-langua.html JSP 2.0 adds a new conditional operator to the Expression Language(EL) to deal with this case in a more elegant way.The conditional operator exists in many programming languages (for instance, in Java, C, and JavaScript), so you may have seen it before. It takes a Boolean condition and one result to use if the condition is true and another if it's false. I use a very simple example to demonstrate the usage : http://www.javabeat.net/tips/173-ternary-operator-in-jsp-20-expression-langua.html http://www.javabeat.net/tips/172-working-with-arrays-javautilarrays-class.html The java.util.Arrays class is basically a set of static methods that are all useful for working with arrays. The Arrays class contains various methods for manipulating arrays (such as sorting and searching). In addition to that, it has got many utility methods for using with arrays such as a method for viewing arrays as lists and methods for printing the contents of an array, whatever be the dimension of the array. http://www.javabeat.net/tips/172-working-with-arrays-javautilarrays-class.html http://www.javabeat.net/tips/171-how-to-use-enum-in-switch.html Prior to Java 1.4, switch only worked with int, short, char, and byte values. However, since enums have a finite set of values, Java 1.5 adds switch support for the enum. Here's an example of using an enum in a switch statement: http://www.javabeat.net/tips/171-how-to-use-enum-in-switch.html http://www.javabeat.net/tips/170-adding-methods-to-an-enum.html Enums introduced in Java 5.0 are just compiled java classes with some extra behaviour. So you can basically do whatever you can in a normal java class inside an enum as well. That includes adding methods , class level variables and constructors to an enum. http://www.javabeat.net/tips/170-adding-methods-to-an-enum.html http://www.javabeat.net/tips/169-volatile-keyword-in-java.html If you are working with the multi-threaded programming, the volatile keyword will be more useful. When multiple threads using the same variable, each thread will have its own copy of the local cache for that variable. So, when it's updating the value, it is actually updated in the local cache not in the main variable memory. The other thread which is using the same variable doesn't know anything about the values changed by the another thread. To avoid this problem, if you declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. http://www.javabeat.net/tips/169-volatile-keyword-in-java.html http://www.javabeat.net/tips/168-what-is-transient-keyword-in-java.html If you want to understand what is transient, then first learn what is serilization concept in Java if you are not familiar with that. Serilization is the process of making the object's state persistent. That means the state of the object is converted into stream of bytes and stored in a file. In the same way we can use the de-serilization concept to bring back the object's state from bytes. This is one of the important concept in Java programming because this serilization is mostly used in the networking programming. The object's which are needs to be transmitted through network has to be converted as bytes, for that purpose ever class or interface must implements Serilization interface. It is a marker interface without any methods. http://www.javabeat.net/tips/168-what-is-transient-keyword-in-java.html http://www.javabeat.net/tips/167-ordering-queue-using-comparator-interface-and.html The basic use of Queue class is to provide a data structure which allows storing objects in a First in First out(FIFO) format. But sometimes one wants to maintain the ordering, based on some other metric. This is exactly the purpose of PriorityQueue, another Queue implementation. You provide it a Comparator, and it does the rest for you. http://www.javabeat.net/tips/167-ordering-queue-using-comparator-interface-and.html http://www.javabeat.net/tips/166-load-on-startup-element-in-webxml.html This tips explains the few points on how to use the load-on-startup element on the web.xml file. When erver is starting, it is possible to tell the container to load a servlet on the startup. You can load any number of servlets on the startup. Normally this is done for any initialization purpose. Look into the following example: http://www.javabeat.net/tips/166-load-on-startup-element-in-webxml.html http://www.javabeat.net/tips/165-scjp-60-certification-rehearse-it-try-it.html Along with the Study guide and Lab Manual, this book comes with a CD containing a Ucertify prepkit with four complete SCJP mock exam papers, study notes and customized test, which should be tried before appearing for the exam. The accompanying CD also contains two mock exams in PDF format and additional questions based on exam objectives. http://www.javabeat.net/tips/165-scjp-60-certification-rehearse-it-try-it.html http://www.javabeat.net/tips/164-packt-publishing-seeks-authors-for-new-beginn.html Packt Publishing seeks authors for new Beginner’s Guide series http://www.javabeat.net/tips/164-packt-publishing-seeks-authors-for-new-beginn.html http://www.javabeat.net/tips/163-how-to-solve-querysyntaxexception-table-is-n.html The above QuerySyntaxException is thrown when we are not mapping the table name properly. The first time hibernate users can be seen this error because you will map the table name directly in the query. That will not work in the hibernate. You will have to map the class name that is mapped in the Hibernate configuration file. Look into the following example: http://www.javabeat.net/tips/163-how-to-solve-querysyntaxexception-table-is-n.html http://www.javabeat.net/tips/162-many-to-one-relationship-in-hibernate-mapping.html This example program demonstrates how to write the many-to-one accociations using the hibernate mapping files. http://www.javabeat.net/tips/162-many-to-one-relationship-in-hibernate-mapping.html http://www.javabeat.net/tips/161-difference-between-hibernates-saveupdate-a.html Hibetnate has set of methods for saving and updating the values in the database. The methods look like same and difficult to differentiate between them if you are not inderstanding them clearly. http://www.javabeat.net/tips/161-difference-between-hibernates-saveupdate-a.html http://www.javabeat.net/tips/160-pagination-using-hibernate-and-jsp.html In the past, I had a few posts on how to implement pagination using displaytag(1, 2). That solution is feasible only with small result sets, the reason being that we will have the entire result set in memory (also called cache based paging). If the result set is large, then having the entire result set in memory will not be feasible. With large result sets, you cannot afford to have them in memory. In such case, you have to fetch a chunk of data at a time (query based paging). The down side of using query based paging, is that there will be multiple calls to the database for multiple page requests. http://www.javabeat.net/tips/160-pagination-using-hibernate-and-jsp.html http://www.javabeat.net/tips/159-junit-40-example.html JUnit 4 introduces a completely different API to the older versions. JUnit 4 uses Java 5 annotations to describe tests instead of using inheritence. It introduces more flexible initialization and cleanup, timeouts, and parameterized test cases. This post describes the new features in JUnit 4, and in the end, I show a basic example that tests the java.util.Stack class. http://www.javabeat.net/tips/159-junit-40-example.html http://www.javabeat.net/tips/158-struts-20-and-spring.html In this post, I will describe how to do the same using Struts 2.0. The only major step that needs to be done here is to override the default Struts 2.0 OjbectFactory. Changing the ObjectFactory to Spring give control to Spring framework to instantiate action instances etc. Most of the code is from the previous post, but I will list only the additional changes here. http://www.javabeat.net/tips/158-struts-20-and-spring.html http://www.javabeat.net/tips/157-circular-linked-list-in-java.html Had to implement a circular linked list recently. Here's my take, suggestions are welcome. The list can be parameterized for any type which has a meaningful equals method defined. The main method shows a sample usage of the Circular linked list with the String type. Only add, remove and size method are implemented. http://www.javabeat.net/tips/157-circular-linked-list-in-java.html http://www.javabeat.net/tips/156-servlet-30.html I can’t wait to see Servlet 3.0 in action. More details about the specification and the current status is available in its JSR homepage. The introduction of support for non-blocking I/O takes Java Servlets to a new level and this, in my opinion,is the most significant stride in Servlet specification since it was introduced. The benefits opened up by this new feature are several. Here are some I can think of - http://www.javabeat.net/tips/156-servlet-30.html http://www.javabeat.net/tips/155-custom-validators-in-struts-20.html Struts 2 allows the use of Custom validators through the @CustomValidator annotation. The @CustomValidator annotation takes two mandatory parameters, type and message http://www.javabeat.net/tips/155-custom-validators-in-struts-20.html http://www.javabeat.net/tips/154-what-is-shale-web-framework.html Apache Shale is a Java Server Faces based Web Application Framework from the Apache software foundation. Shale is talked of as the "heir" Apache struts framework. We all know that struts is the most used Java Web Framework so far. While shale is the successor of Struts, there is a significant departure of architecture from sturts to shale. Firstly, while struts is based on a monolithic Request Processor, Shale is set of fine-grained services that can be combined as needed to meet particular application needs. Secondly, while sturts can be integrated with Java Server Faces, Shale is built upon JSF. http://www.javabeat.net/tips/154-what-is-shale-web-framework.html http://www.javabeat.net/tips/153-how-to-delete-a-cookie-on-server-in-a-j2ee-ap.html There is no direct method offered by servlet API to delete a cookie on server side. This is how you can go about doing it. http://www.javabeat.net/tips/153-how-to-delete-a-cookie-on-server-in-a-j2ee-ap.html http://www.javabeat.net/tips/152-ejb-webservices-in-jboss-application-server-s.html EJB Webservices in JBoss application server sample code http://www.javabeat.net/tips/152-ejb-webservices-in-jboss-application-server-s.html http://www.javabeat.net/tips/151-how-to-enable-ssl-on-jboss-application-server.html To enable SSL on JBoss add the following segment to JBOSS_HOME/server/default/deploy/jbossweb-tomcatxx.sar/server.xml as a child of the jboss.web Service element. http://www.javabeat.net/tips/151-how-to-enable-ssl-on-jboss-application-server.html http://www.javabeat.net/tips/150-sample-code-for-simpledateformat.html Sample code for SimpleDateFormat http://www.javabeat.net/tips/150-sample-code-for-simpledateformat.html http://www.javabeat.net/tips/149-sample-code-for-listing-file-names-in-a-direc.html Sample code for Listing file names in a directory http://www.javabeat.net/tips/149-sample-code-for-listing-file-names-in-a-direc.html http://www.javabeat.net/tips/148-advantages-and-disadvantages-jsf.html JSF is becoming more popular framework for user interface layer development, many architects and companies assuming that Struts is becoming outdated and JSF is catching up the market. I am not sure whether it is true at this point of time. However I would like express my critic on the advantages and disadvantages of JSF. http://www.javabeat.net/tips/148-advantages-and-disadvantages-jsf.html http://www.javabeat.net/tips/147-custom-datetimeconverter-in-jsf.html By default JSF using GMT timezone to convert the date into display format. http://www.javabeat.net/tips/147-custom-datetimeconverter-in-jsf.html http://www.javabeat.net/tips/146-hgraphicimage-in-jsf.html In a JavaServer Faces application, the UIGraphic component represents an image. The graphicImage tag is used to render a UIGraphic component on a page.The url attribute specifies the path to the image. It also corresponds to the local value of the UIGraphic component so that the URL can be retrieved, possibly from a backing bean. The URL of the example tag begins with a /, which adds the relative context path of the web application to the beginning of the path to the image. http://www.javabeat.net/tips/146-hgraphicimage-in-jsf.html http://www.javabeat.net/tips/145-new-features-in-jsp-20.html JSP 2.0 is released with new promises. JSP 2.0 is an upgrade to JSP 1.2 with several new and interesting features. These features makes the life of web application developers http://www.javabeat.net/tips/145-new-features-in-jsp-20.html http://www.javabeat.net/tips/144-benefits-of-using-web-services.html Exposing the function on to network: A Web service is a unit of managed code that can be remotely invoked using HTTP, that is, it can be activated using HTTP requests. So, Web Services allows you to expose the functionality of your existing code over the network. Once it is exposed on the network, other application can use the functionality of your program. http://www.javabeat.net/tips/144-benefits-of-using-web-services.html http://www.javabeat.net/tips/143-what-is-soa.html Service Oriented Architecture or SOA for short is a new architecture for the development of loosely coupled distributed applications. In fact service-oriented architecture is collection of many services in the network. These services communicate with each other and the communications involves data exchange and even service coordination. Earlier SOA was based on the DCOM or Object Request Brokers (ORBs). Nowadays SOA is based on the Web Services. http://www.javabeat.net/tips/143-what-is-soa.html http://www.javabeat.net/tips/142-what-is-web-20.html Web 2.0, a phrase is a cluster term for the new phase of World Wide Web, which was coined by O’Reilly and Media live International in 2003 and popularized by the first Web 2.0 conference in 2004. There is no certain definition of Web 2.0, even though; it stands for the transformation of the web into a full-fledged computing platform. http://www.javabeat.net/tips/142-what-is-web-20.html http://www.javabeat.net/tips/141-what-is-web-30.html Web 3.0 is a term, which definition is not confirmed or defined so far as several experts have given several meaning, which do not match to each other, but sometimes it is referred to as a Semantic Web. In the context of Semantic Web, Web 3.0 is an evolving extension of the World Wide Web in which web content can be expressed not only in natural language, but also in a form that can be understood, interpreted and used by software agents, thus permitting them to find, share and integrate information more easily. http://www.javabeat.net/tips/141-what-is-web-30.html http://www.javabeat.net/tips/140-request-lifecycle-in-struts-20-applications.html Struts and webwork has joined together to develop the Struts 2 Framework. Struts 2.0 Framework is very extensible and elegant for the development of enterprise web application of any size. In this section we are going to explain you the architecture of Struts 2.0 Framework. http://www.javabeat.net/tips/140-request-lifecycle-in-struts-20-applications.html http://www.javabeat.net/tips/139-struts-10-vs-struts-20.html In the following section, we are going to compare the various features between the two frameworks. Struts 2.x is very simple as compared to struts 1.x, few of its excelent features are: http://www.javabeat.net/tips/139-struts-10-vs-struts-20.html http://www.javabeat.net/tips/138-what-is-adobe-flex.html Flex is a programming language developed on adobe technology to enhance the users capability in building rich internet applications. This latest adobe technology possesses all flash features. Flex is embedded with two languages MXML and Action Script respectively. Among all known scripting languages Action Script is one of them that comes along with Flex. Adobe Flex uses Sun's Java Environment for developing Rich Internet applications (RIA's). Flex coding is done with an XML based language known as MXML and like Flash applications, Flex codes too are compiled into a file having SWF format called ShockWave Flash files. These SWF files are executed with stand-alone Adobe's Flash Players, and can also be directly executed in browsers that have Adobe Flash Player Plug-in installed. http://www.javabeat.net/tips/138-what-is-adobe-flex.html http://www.javabeat.net/tips/137-mixing-generics-and-non-generics-code.html If we are work on code that uses generics that is fine and what will happen if we want to mix both generic and non generic code. http://www.javabeat.net/tips/137-mixing-generics-and-non-generics-code.html http://www.javabeat.net/tips/136-how-to-use-extends-in-generics.html In generics as we know we can not assign subclass generic type to super class generic type, for example http://www.javabeat.net/tips/136-how-to-use-extends-in-generics.html http://www.javabeat.net/tips/135-using-super-in-generics-java-50.html As we know we can not add any value except null to collection if we use ? extends syntax. http://www.javabeat.net/tips/135-using-super-in-generics-java-50.html http://www.javabeat.net/tips/134-generic-methods-in-java-50.html In java 1.5 we have a feature called generic methods, with this we can write a method, which can be generic, means it can be called by any parameter and behavior of the method will be according to the parameter passed. http://www.javabeat.net/tips/134-generic-methods-in-java-50.html http://www.javabeat.net/tips/133-handle-exceptions-in-overriding-methods.html The question why makes any topic makes more clearer and interesting than just to know about what the concept is. http://www.javabeat.net/tips/133-handle-exceptions-in-overriding-methods.html http://www.javabeat.net/tips/132-life-cycle-of-jsf-components.html The JSF servlet builds the view of the requested page as a component tree that contains the information associated with all components. It also saves the view in a FacesContext instance, thereby making it possible to repopulate the page if necessary—for example, when the user doesn’t fill out a form as required. If the same page was displayed before and component states were saved, that information would also be taken into account. In this phase, JSF wires event handlers and validators (if any) to the components. http://www.javabeat.net/tips/132-life-cycle-of-jsf-components.html http://www.javabeat.net/tips/131-hiding-and-overriding-methods-in-java.html Here the overriding methods getX and getY in class RealPoint have the same return types as the methods of class Point that they override, so this code can be successfully compiled. http://www.javabeat.net/tips/131-hiding-and-overriding-methods-in-java.html http://www.javabeat.net/tips/130-static-keyword-in-java.html static variables and methods might better have been called perClass variables and methods. They inherited this misleading terminology from C++. They are the opposite of instance variables and methods that work on a particular object. http://www.javabeat.net/tips/130-static-keyword-in-java.html http://www.javabeat.net/tips/129-decorator-design-pattern.html You want to add behavior or state to individual objects at runtime.Inheritance is not feasible because it is static and applies to an entire class. http://www.javabeat.net/tips/129-decorator-design-pattern.html http://www.javabeat.net/tips/128-iterator-pattern.html Provide a way to access the elements of the aggregate object sequentially without exposing its underlying representation. Aggregate object is an object that contains other objects for the purpose of grouping those objects as a unit.It is also called a container or a collection. http://www.javabeat.net/tips/128-iterator-pattern.html http://www.javabeat.net/tips/127-abstract-factory-pattern.html Provide an interface for creating families of related or dependent objects without specifying their concrete classes. http://www.javabeat.net/tips/127-abstract-factory-pattern.html http://www.javabeat.net/tips/126-template-design-pattern.html An abstract class defines various methods and has one non-overridden method which calls the various methods. http://www.javabeat.net/tips/126-template-design-pattern.html http://www.javabeat.net/tips/125-closures-in-java-70.html A closure is a function that is evaluated in an environment containing one or more bound variables.(Free variables which are to be passed to the function).In some languages closures may occur when a function is defined within another function and the inner function refers to the local variables of the outer function.At runtime when outer function executes, a closure is formed consisting of inner function's code and references to any variables of the outer function required by the closure. http://www.javabeat.net/tips/125-closures-in-java-70.html http://www.javabeat.net/tips/124-inner-classes-in-java.html Nested classes that are not inner classes may declare static members freely, in accordance with the usual rules of the Java programming language. Member interfaces are always implicitly static so they are never considered to be inner classes.A statement or expression occurs in a static context if and only if the innermost method, constructor, instance initializer, http://www.javabeat.net/tips/124-inner-classes-in-java.html http://www.javabeat.net/tips/123-abstract-keyword-in-java.html As we all know,An abstract method declaration introduces the method as a member, providing its signature, return type, and throws clause , but does not provide an implementation. Every subclass of A that is not abstract must provide an implementation for m, or a compile-time error occurs. http://www.javabeat.net/tips/123-abstract-keyword-in-java.html http://www.javabeat.net/tips/122-jsf-best-practices.html Here I am documenting some best practices can be followed during JSF project development. http://www.javabeat.net/tips/122-jsf-best-practices.html http://www.javabeat.net/tips/121-threadlocal-in-java.html ThreadLocal is one of the rarely used class in Java. I found it is one of the powerful class in Java on multi-threaded programming. In multi threaded program generally we use session object to track the current users information. http://www.javabeat.net/tips/121-threadlocal-in-java.html http://www.javabeat.net/tips/120-why-multiple-inheritance-is-not-allowed-in-ja.html For long time I had a question “why Sun introduced Interface concept instead of C++ style of multiple inheritance?”. I did googling but many articles and forums talks about difference between abstract class and Interface not why Interface concept required in Java. After extensive search and analysis I came to know the reason behind the Interface concept in Java. http://www.javabeat.net/tips/120-why-multiple-inheritance-is-not-allowed-in-ja.html http://www.javabeat.net/tips/119-how-to-install-tomcat-60-server.html This article explains how to install the tomcat 6.0 server in your desktop. This is pretty simple and since moss of the java beginners find its difficult to get started with the web development. Because tomcat is the mostly recommended web server for learning JSP and Servlets basics. Tomcat is also the Reference Implementation(RI) for JSP and Servlet specification. http://www.javabeat.net/tips/119-how-to-install-tomcat-60-server.html http://www.javabeat.net/tips/118-servlet-life-cycle.html Before start writing the servlet, it is important to know the life cylce of every servlet instance created. Read What is Servlet? tips to know about the servlet basics. http://www.javabeat.net/tips/118-servlet-life-cycle.html http://www.javabeat.net/tips/117-sar-service-archive-file-in-jboss.html This tips explains how to create and deploy the SAR file in the JBoss application server. SAR files are only used in the JBoss application server. It cannot be used in the other application server environments. Before looking into creating a SAR file, first let you know what is SAR file. http://www.javabeat.net/tips/117-sar-service-archive-file-in-jboss.html http://www.javabeat.net/tips/116-new-features-in-jsf-20.html JSF 2.0 proposal has been posted on March 2007 and planned for the release in last quarter of 2008. It will be shipped with JEE 6.0 release. Looking into the features lits of the JSF 2.0, it is added lots of interesting features in the list and also they are aiming to attract more new developers to use JSF technology. http://www.javabeat.net/tips/116-new-features-in-jsf-20.html http://www.javabeat.net/tips/115-new-features-in-servlet-30.html The next version for servlet technology is Servlet 3.0, which is planned to be released with JEE 6.0 in the last quarter of 2008. After the release of servlet 2.5 in spetember 2005, this is the new version with many new features included. Servlet 2.5 is released with JEE 5.0. Servlet 3.0 is maintained by the JSR 315. http://www.javabeat.net/tips/115-new-features-in-servlet-30.html http://www.javabeat.net/tips/114-what-is-servlet.html Java Servlet is the serverside Java programming language. We can say it as serverside applet. How applet is used for writing the client side code, servlet is used for writing the serverside programming language. Servlet programming is first created by Sun Microsystems in June 1997. The latest version is Servlet 2.5 which is released with JEE 5.0 specification. Servlet is a specification and it can be implemented by anyone who can fulfil the mandatory requirements of the specification maintained by Sun. http://www.javabeat.net/tips/114-what-is-servlet.html http://www.javabeat.net/tips/113-call-java-oracle-functions-from-java-program.html Beginning with version 8i, the Oracle database includes a fully functional Java Virtual Machine, Oracle JVM. Out of this close relationship between Oracle and Java emerges an important technology for Oracle developers: Java stored procedures. With Java stored procedures, developers have the ability to harness the power of Java when building database applications. This article provides an overview of this increasingly popular technology. Its intended audience is Java developers new to Oracle, and Oracle PL/SQL developers with a basic understanding of Java. http://www.javabeat.net/tips/113-call-java-oracle-functions-from-java-program.html http://www.javabeat.net/tips/112-configure-mysql-database-with-hibernate-mappi.html Configuring MySql database with hibernate is the same as with other databasses.The only difference will be connection url and the database dialect to be specified in the configuration file. This tips provides a basic example configuration file for configuaring the MySql with hibernate. But it doesnot explain you installing the MySql database. http://www.javabeat.net/tips/112-configure-mysql-database-with-hibernate-mappi.html http://www.javabeat.net/tips/111-collection-mapping-in-hibernate-one-to-many.html This article explains how to map two classes in collection mapping. In this example one Author object has the list of Book objects. Both the classes are mapped and will be inserted together into the database. Here this example uses Bag as the collection type. Other collection types available are Set,List,Array. Look into the example programs for more detail. http://www.javabeat.net/tips/111-collection-mapping-in-hibernate-one-to-many.html http://www.javabeat.net/tips/110-comparision-operators-in-hibernate.html HQL supports all the operators used in the SQL language. But, Criteria API doesn't support the arithmetic expressions. Apart from that, it is easy to use other operators in the Criteria API itself. This tips provides few basic example programs on using the operators. http://www.javabeat.net/tips/110-comparision-operators-in-hibernate.html http://www.javabeat.net/tips/109-null-and-not-null-comparision-in-the-hibernat.html While checking for the null and not null values in the Hibernate API, we have to be careful and there is chance for misunderstanding. This tips explains how to compare the null values in the Hibernate query. http://www.javabeat.net/tips/109-null-and-not-null-comparision-in-the-hibernat.html http://www.javabeat.net/tips/108-how-to-use-named-parameters-and-named-query-i.html There is two types of query parameters binding in the Hibernate Query. One is positioned parameter and another one is named parameters. But, hibernate recommend to use the named parameters since it is more flexible and powerful compare to the positioned parameter. http://www.javabeat.net/tips/108-how-to-use-named-parameters-and-named-query-i.html http://www.javabeat.net/tips/107-pagination-in-hibernate-query-api.html Pagination is the very common problem for the most of the eneterprise applications. When we are retrieving thousands of records from the database, it is not good idea to retrieve all the records at the same time. So, we have to implement some sort of pagination concept in your application to restrict the number of rows to be fetched from the database. http://www.javabeat.net/tips/107-pagination-in-hibernate-query-api.html http://www.javabeat.net/tips/106-three-ways-to-create-query-in-hibernate.html To create query in the Hibernate ORM framework, there is three different types. The folloing are the three ways to create query instance: http://www.javabeat.net/tips/106-three-ways-to-create-query-in-hibernate.html http://www.javabeat.net/tips/105-how-to-use-initialization-callback-methods-wh.html Springframework provides flexibility to initialize its Beans using the user defined methods. There is some scenario where application developer want to initialize the beans properties after setting all the values. The following example program demonstrates by defining a custom method to initialize the calues. http://www.javabeat.net/tips/105-how-to-use-initialization-callback-methods-wh.html http://www.javabeat.net/tips/104-stringbuilder-class-in-java-50.html StringBuilder class is introduced in Java 5.0 version. This class is replacement for the existing StringBuffer class. If you look into the operations of the both the classes, there is no difference. http://www.javabeat.net/tips/104-stringbuilder-class-in-java-50.html http://www.javabeat.net/tips/103-writing-simple-ant-build-script.html This article explains how to write a very basic ANT build script. This does not explain indepth knowledge on building your project using ANT script. But, this writeup will be more useful for the beginners who haben't writen any ANT script before. Before start writing the script, lets look into how to install the ANT in your machine. http://www.javabeat.net/tips/103-writing-simple-ant-build-script.html http://www.javabeat.net/tips/102-implement-internationalization-and-localizati.html Internationalization and Localization are important features for an web based application. Internationalization is implementing the features in your application to support multiple languages. Localization is creating text in a specific language that is presented through an internationalized application http://www.javabeat.net/tips/102-implement-internationalization-and-localizati.html http://www.javabeat.net/tips/101-chain-of-responsibility-pattern-in-java.html A method called in one class will move up a class hierarchy until a method is found that can properly handle the call.It consists of a source of command objects and a series of processing objects.Each processing object contains a set of logic that describes the types of command objects that it can handle,and how to pass off those that it cannot to the next processing object in the chain.A mechanism also exists to add new processing objects in the chain. http://www.javabeat.net/tips/101-chain-of-responsibility-pattern-in-java.html http://www.javabeat.net/tips/100-comparing-objects-in-java.html In Java comparing two value object is not straight forward. Here we will see how we can compare two value objects in Java. http://www.javabeat.net/tips/100-comparing-objects-in-java.html http://www.javabeat.net/tips/99-how-to-use-datasource-in-hibernate-applicatio.html This article explains how to configure datasource in the JBoss application server and how to use the same datasource in the hibernate configuration file. Before looking into the hibernate configuration, we will satrt with creating datasource inside JBoss application server. http://www.javabeat.net/tips/99-how-to-use-datasource-in-hibernate-applicatio.html http://www.javabeat.net/tips/98-hibernate-criteria-query-example.html Criteria APIs in the hibernate framework is useful for creating the dynamic query to execute. It is an alternative way to write the queries without using HQL. The queries are generated at runtime and excuted on the fly. Application developer need not worry about writing the query in hand, he/she just need to use APIs provided in the hibernate. It is one of the elegant way to write the queries in hibernate. http://www.javabeat.net/tips/98-hibernate-criteria-query-example.html http://www.javabeat.net/tips/97-how-to-lazy-initialize-spring-beans.html As we know Spring's bean factory is pre-initiate all the beans when first time creating the facory. This is good practise because if there is any dependency error everything can be resolved at the time of startup. This is not case in all the application scnarios. http://www.javabeat.net/tips/97-how-to-lazy-initialize-spring-beans.html http://www.javabeat.net/tips/95-inner-beans-in-spring-ioc.html Spring IOC allows Inner Beans declaration. We can declare a bean inside a beans. But, it has few restriction. Inner Beans are like annonymous beans where it is created and used on the fly. this beans cannot be used outside the enclosing beans. So, it is wise to avoid declaring the 'ID' or 'SCOPE' attributes for them. Because, these values will be ignored by the container. Only the enclosing beans can access them. http://www.javabeat.net/tips/95-inner-beans-in-spring-ioc.html http://www.javabeat.net/tips/94-setter-injection-in-spring-ioc.html This article presents how to write the Constructor Injection in Spring IOC. There is two types of Dependency Injection(DI) techniques we can use. 1) Setter Injection and 2) Constructor Injection. http://www.javabeat.net/tips/94-setter-injection-in-spring-ioc.html http://www.javabeat.net/tips/93-constructor-injection-in-spring-ioc.html This article presents how to write the Constructor Injection in Spring IOC. There is two types of Dependency Injection(DI) techniques we can use. 1) Setter Injection and 2) Constructor Injection. http://www.javabeat.net/tips/93-constructor-injection-in-spring-ioc.html http://www.javabeat.net/tips/92-how-to-configure-hibernate-using-xml-files.html Using XML files for configuring hibernate application is the most widely used approach. This is simple one and less whanges needed in the future. There is two types of configuration we can do using XML files. one is non-managed environment and another one is for managed environment. Here we will explain about the non-managed environment or standalone program. In the managed environment you can use datasourec for establishing connection to the database instead directly specifying all the properties in the configuration file. http://www.javabeat.net/tips/92-how-to-configure-hibernate-using-xml-files.html http://www.javabeat.net/tips/91-creating-simple-toolbar-using-richfaces-tag-l.html This example demonstrates how to create simple toolbar using RichFaces tag library. RichFaces provides predefined tags like rich:toolBar which will be easily plugged into our webpages to disply the toolbar component. Apart from rich:toolBar, to create menus we have to use other tags rich:dropDownMenu and rich:menuItem. http://www.javabeat.net/tips/91-creating-simple-toolbar-using-richfaces-tag-l.html http://www.javabeat.net/tips/90-use-richdatascroller-for-richdatatable-pagi.html rich:dataTable tag is the RichFaces version fo datatable component which has few extra features on look and feel.One of the difficulty JSF developers is creating good pagination for the data dsiplayed using rich:datatable. To resole this problem, RichFaces tags library provides rich:datascroller component which can display the automatic paginations based on data populated using rich:dataTable. http://www.javabeat.net/tips/90-use-richdatascroller-for-richdatatable-pagi.html http://www.javabeat.net/tips/89-use-a4jstatus-to-display-status-of-the-reque.html When there is a request to the server, the client have to wait untill he gets the response. It will be nice if you give status of the server request processing. use a4j:status tag in the RichFaces to implement this feature in your webpages. In this example this tag is used with a4j:support and showing the status message while user types in the text field. http://www.javabeat.net/tips/89-use-a4jstatus-to-display-status-of-the-reque.html http://www.javabeat.net/tips/88-a4jsupport-how-to-use-action-attribute.html This example program demonstrates how to use action attribute to update the server values and display in the screen. In this example user inputs are passed to update method and processed. The values are updated in the h:panelGrid component. The advantage of using a4j:support tag is it can be updated the whole region by specifying the reRender attribute. http://www.javabeat.net/tips/88-a4jsupport-how-to-use-action-attribute.html http://www.javabeat.net/tips/87-a4jsupport-simple-example-on-onkeyup-event.html This example program demonstrates how to get started with a4j:support tag in the RiachFaces tag libraray. This is part of Ajax4jsf libraray. But, from RiachFaces 3.0, Ajax4jsf is merged with RichFaces tag libraray. a4j:support is used inside any component to provide ajax support on that particular field. http://www.javabeat.net/tips/87-a4jsupport-simple-example-on-onkeyup-event.html http://www.javabeat.net/tips/86-how-to-write-throws-advice-in-spring-aop.html Throws Advice is used when throwing exception from the business methods. This interceptor will be called when there is any exception, so one can do any logic to candle the exception. http://www.javabeat.net/tips/86-how-to-write-throws-advice-in-spring-aop.html http://www.javabeat.net/tips/85-how-to-write-interception-around-advice-in-sp.html In this tips we explore how to use the Interception Around Advice in Spring's Aspect Oriented Programming(AOP). Interception Around Advice is fundamental advice type in the Spring framework. Also this advice type is derived from other frameworks like AspectJ. So it is interoporable with other framework, other advices in the Spring AOPs are specific to Spring Framework and cannot be used in the other similar frameworks. http://www.javabeat.net/tips/85-how-to-write-interception-around-advice-in-sp.html http://www.javabeat.net/tips/84-simple-example-for-before-advice-and-after-ad.html This tips presents a very simple program for invoking the Before Advice and After Advice in the Spring Framework. Thsese two methods are part of Spring's AOP implementation and used as interceptor methods. http://www.javabeat.net/tips/84-simple-example-for-before-advice-and-after-ad.html http://www.javabeat.net/tips/83-editing-eclipse-classpath-file.html While creating a project in Eclipse, by default it creates a .classpath file in the project directory. That file will be usedfor storing file names and other dependent files needed in the classpath to compile and execute the project successfully. http://www.javabeat.net/tips/83-editing-eclipse-classpath-file.html http://www.javabeat.net/tips/82-baisc-steps-to-configure-log4j-using-xml-and.html This example demonstrated how to configure Log4j setup using the Proerties file and XML file. These are the two most widely used techniques for configuring the Log4j for your application. But, in the recent days configuring with properties files are considered to be old technique and recommended using XML. http://www.javabeat.net/tips/82-baisc-steps-to-configure-log4j-using-xml-and.html http://www.javabeat.net/tips/81-batch-insert-in-hibernate.html This example program shows how to insert multiple rows using the batch processing in hibernate. when there are thousand of rows to be persisted, everytime iterating and inserting will cause the memory problem. Hibernate stored all the persisted objects in the memory. To avoid this problem use batch processing in the hibernate. http://www.javabeat.net/tips/81-batch-insert-in-hibernate.html http://www.javabeat.net/tips/80-hibernate-basic-configuration-example.html This example demonstrates how to configure hibernate framework for running a simple standalone program. Here the sample program uses programmatic configuration to set all the properties required for running hibernate. Also the example uses derby as the database to connect and update the values. This is not the big change, you only have to change few parameters if you are using any other databases. http://www.javabeat.net/tips/80-hibernate-basic-configuration-example.html http://www.javabeat.net/tips/79-accessing-managed-bean-methods-programmatical.html As we know JSF managed beans are mostly access only through the JSP pages are faces-config.xml. But, there is some schenarios where you will need information stored in the managed beans for the business logic in some other beans. JSF provides API to access those values where ever you want. http://www.javabeat.net/tips/79-accessing-managed-bean-methods-programmatical.html http://www.javabeat.net/tips/78-how-to-use-managed-bean-reference-inside-face.html Managed Bean in JSF can refer another managed bean inside the faces-config.xml. There is no restriction for the type of bean can be refered. But, JSF does not support the cyclic dependencies for Managed Bean reference. For example, you cannot refer bean B from bean A while bean B also refers to bean A. The following simple program demonstrates how to refer a listBean inside a normal JSF Managed Bean. For simplicity purpose this example use List as managed bean. You can use any type of bean for the reference. http://www.javabeat.net/tips/78-how-to-use-managed-bean-reference-inside-face.html http://www.javabeat.net/tips/77-how-to-initialize-map-property-in-managed-mea.html JSF Managed Beans can initialize its Map properties in the faces-config.xml. There is a property in the faces-config.xml as map-entries. This cane be used for initializing the values and can be accessed directly through the Managed Beans in any JSP pages. http://www.javabeat.net/tips/77-how-to-initialize-map-property-in-managed-mea.html http://www.javabeat.net/tips/76-how-to-initialize-list-property-in-managed-me.html JSF Managed Beans can initialize its List properties in the faces-config.xml. There is a property in the faces-config.xml as list-entries. This cane be used for initializing the values and can be accessed directly through the Managed Beans in any JSP pages. http://www.javabeat.net/tips/76-how-to-initialize-list-property-in-managed-me.html http://www.javabeat.net/tips/74-lists-and-maps-as-managed-beans-in-jsf.html This tips explain how to use List and Map classes directly as Managed Beans. Here notice that you cannot use List and Map interfaces directly as Managed Beans, you can use only the implementations classes like ArrayList, Map,etc. There is no way to call constructor in the interfaces if you use List or Map directly. http://www.javabeat.net/tips/74-lists-and-maps-as-managed-beans-in-jsf.html http://www.javabeat.net/tips/73-publish-and-subscribe-messages-using-jms-topi.html This tips gives overview on how to write Java Messaging Service(JMS) code for creating Topic in the Tomcat server. This is very basic example and only show how to get started instead of looking into the advanced concepts in JMS technology. http://www.javabeat.net/tips/73-publish-and-subscribe-messages-using-jms-topi.html http://www.javabeat.net/tips/72-how-to-use-hselectoneradio-inside-hdatatabl.html This tips explains how to use the h:selectOneRadio tag inside h:dataTable iteration tag. Using h:selectOneRadio is not straight forward since JSF dowsn't provide easy mechanism for toggling the radio button selectios. Programmer has to write the manual script code to toggle the radio selections. http://www.javabeat.net/tips/72-how-to-use-hselectoneradio-inside-hdatatabl.html http://www.javabeat.net/tips/71-write-your-own-validator-in-jsf.html This tips presents sample programs for how to write the custom validator in JSF application. There is many built-in validators available in JSF. http://www.javabeat.net/tips/71-write-your-own-validator-in-jsf.html http://www.javabeat.net/tips/70-create-simple-custom-converter-implementation.html This article explains the simple Converter class implementation. Converter class is used for converting any given input to the desired output format or with any business logic to the input values. This example also includes the PhaseListener to identify in which JSF lifecycle phase the convertion happens. http://www.javabeat.net/tips/70-create-simple-custom-converter-implementation.html http://www.javabeat.net/tips/69-how-to-implement-fphaselistener-for-hcomman.html How to implement f:phaseListener for h:commandButton? - PhaseListener in JSF http://www.javabeat.net/tips/69-how-to-implement-fphaselistener-for-hcomman.html http://www.javabeat.net/tips/68-how-to-read-xml-file-and-inject-bean-referenc.html This article presents sample source code for creating the Bean instance using the Spring Framework. This is basic example to read configuration file from the file system and create the beans from the applicationContext.xml file. This xml file define two beans Employee and Address. http://www.javabeat.net/tips/68-how-to-read-xml-file-and-inject-bean-referenc.html http://www.javabeat.net/tips/67-how-to-implement-actionlistener-factionlist.html This article explains how to implement the ActionListener class in the JSF core tag library. An ActionListener is an event handler interface for a class that can respond to user events in your JSF page. The body content of this tag must be empty. http://www.javabeat.net/tips/67-how-to-implement-actionlistener-factionlist.html http://www.javabeat.net/tips/66-fconvertdatetime-tag-in-jsf.html f:convertDateTime is used for validating the date input. If the user enters any invlid input, it will throw the error message to the screen. Also it allows the user to specify the apttern of date format using the 'pattern' attribute. http://www.javabeat.net/tips/66-fconvertdatetime-tag-in-jsf.html http://www.javabeat.net/tips/65-houtputformat-tag-in-jsf.html The outputFormat tag renders parameterized text and allows you to customize the appearance of this text using CSS styles. Parameterized text is compound text containing placeholder values to be replaced by actual values at rendering time. http://www.javabeat.net/tips/65-houtputformat-tag-in-jsf.html http://www.javabeat.net/tips/64-fconvertnumber-tag-in-jsf.html This tag is used to register the NumberConverter instance on the enclosing component. This class is responsible to convert String to java.util.Number object and vice-versa. http://www.javabeat.net/tips/64-fconvertnumber-tag-in-jsf.html http://www.javabeat.net/tips/63-create-ejb-30-project-in-netbeans-61.html This article explains how to create EJB 3.0 project using NetBeans IDE 6.1. This article will not explain the details of EJB 3.0 but will give basic knowledge on how to create simple EJB 3.0 project using NetBeans 6.1 IDE. http://www.javabeat.net/tips/63-create-ejb-30-project-in-netbeans-61.html http://www.javabeat.net/tips/62-entity-beans-in-ejbbmp.html Thus far, we acquainted ourselves with Sessionbeans ( both stateless and stateful) and also CMP Entity bean. In this instalment, we take up the most difficult type, (ie) Bean-Managed Persistent Entity bean.(BMP) http://www.javabeat.net/tips/62-entity-beans-in-ejbbmp.html http://www.javabeat.net/tips/61-entity-beans-in-ejbcmp.html As already mentioned ,Entity beans can be thought of as a record ( or row) in a table of a relational database. ( This is just for easy understanding because, the database can also be Object Database, XML database etc.) http://www.javabeat.net/tips/61-entity-beans-in-ejbcmp.html http://www.javabeat.net/tips/60-java-security-packages-using-jcajce.html In this tutorial, the author explains the cryptography-related concepts and packages in JDK,with code examples.Many of the concepts and technical terms thus learnt will be useful in understanding the Cryptography API in MFC also. http://www.javabeat.net/tips/60-java-security-packages-using-jcajce.html http://www.javabeat.net/tips/59-java-messaging-servicejms.html A brief note and demo for JMS ( Java Messaging Service) http://www.javabeat.net/tips/59-java-messaging-servicejms.html http://www.javabeat.net/tips/58-jstl-sql-tags.html In this fourth and last part of the tutorial on JSTL,the author deals with the 'sql' tags in JSTL and shows how they greatly simplify simple database operations like 'select' queries. In another demo, common database operations like 'add','modify' , 'delete' and 'verify'also are dealt with. http://www.javabeat.net/tips/58-jstl-sql-tags.html http://www.javabeat.net/tips/57-jstl-xml-tags.html In this third part of the tutorial on JSTL, the author explains the use of xml tags of the JSTL and shows their wonderful simplicity ,ease of use and raw power. http://www.javabeat.net/tips/57-jstl-xml-tags.html http://www.javabeat.net/tips/56-core-tags-in-jstl.html In the second part of this tutorial on JSTL, the author explains how the tags in the core-group can be used in JSP pages, with a number of simple examples. http://www.javabeat.net/tips/56-core-tags-in-jstl.html http://www.javabeat.net/tips/55-an-introduction-to-jstl.html As J2EE programmers, we are familiar with Servlets , JSP and JavaBeans. Any JSP page should encapsulate the business logic in a bean and invoke it by using jsp:useBean tag. Till recently, a combination of Servlets, JSP and beans was the standard practice. But, the JCP realeased an API for enabling programmers to create custom tags and use them in their JSP pages. The difference between javabean and java custom tags was that, though both made use of java classes, tags can be used by non-programmers also without knowledge of Java programming, just as they would use html tags.( From a programmers perspective,however, a much more important distinction is that tags are specific to the page in which they are created while javabeans are general. ) http://www.javabeat.net/tips/55-an-introduction-to-jstl.html http://www.javabeat.net/tips/54-getting-started-with-flex-20.html Flex2 is the latest RIA technolgy based on MXML and Flash.Originally from Macromedia, this software is now being provided by Adobe, as Adobe has recently acquired Macromedia. The Flex2 software was given in DeveloperIQ CD in August-2006. That edition carried a very interesting and informative interview with Dave Gruber of Adobe by the editor Mr.Ramdas. Flex2 is being positioned and promoted as a better technology than Ajax. ( this is the impression that we gain, from their advertisements in JavaLobby site). The aim of this introductory tutorial is to explore the technology at a very basic level. However, what we see by these basic experiments is that it is just like DotNet Framework and ASP.net , atleast so far as naming of controls etc are concerned and partly like an applet( it is executed in client-side). http://www.javabeat.net/tips/54-getting-started-with-flex-20.html http://www.javabeat.net/tips/53-what-is-spring.html Spring is grate framework for development of Enterprise grade applications. Spring is a light-weight framework for the development of enterprise-ready applications. Spring can be used to configure declarative transaction management, remote access to your logic using RMI or web services, mailing facilities and various options in persisting your data to a database. Spring framework can be used in modular fashion, it allows to use in parts and leave the other components which is not required by the application. http://www.javabeat.net/tips/53-what-is-spring.html http://www.javabeat.net/tips/52-display-error-messages-in-jsf-hmessages-.html Display error messages in JSF [ h:messages ] - part 1 http://www.javabeat.net/tips/52-display-error-messages-in-jsf-hmessages-.html http://www.javabeat.net/tips/51-hselectonemenu-java-server-faces-jsf.html h:selectOneMenu - Java Server Faces (JSF) http://www.javabeat.net/tips/51-hselectonemenu-java-server-faces-jsf.html http://www.javabeat.net/tips/50-hselectmanymenu-java-server-faces-jsf.html h:selectManyMenu - Java Server Faces (JSF) http://www.javabeat.net/tips/50-hselectmanymenu-java-server-faces-jsf.html http://www.javabeat.net/tips/49-hselectmanycheckbox-java-server-faces-jsf.html h:selectManyCheckBox - Java Server Faces (JSF) http://www.javabeat.net/tips/49-hselectmanycheckbox-java-server-faces-jsf.html http://www.javabeat.net/tips/48-hselectbooleancheckbox-java-server-faces-.html h:selectBooleanCheckBox - Java Server Faces (JSF) http://www.javabeat.net/tips/48-hselectbooleancheckbox-java-server-faces-.html http://www.javabeat.net/tips/47-how-to-use-resource-bundle-in-jsf.html How to use Resource Bundle in JSF? http://www.javabeat.net/tips/47-how-to-use-resource-bundle-in-jsf.html http://www.javabeat.net/tips/46-hdatatable-java-server-faces-jsf.html h:dataTable - Java Server Faces (JSF) http://www.javabeat.net/tips/46-hdatatable-java-server-faces-jsf.html http://www.javabeat.net/tips/45-how-to-set-selected-tab-in-richtabpanel-tag.html How to set selected tab in rich:tabPanel tag? http://www.javabeat.net/tips/45-how-to-set-selected-tab-in-richtabpanel-tag.html http://www.javabeat.net/tips/44-hcommandlink-how-to-pass-parameter-to-next.html h:commandLink - How to pass Parameter to next page? http://www.javabeat.net/tips/44-hcommandlink-how-to-pass-parameter-to-next.html http://www.javabeat.net/tips/43-how-to-use-hselectbooleancheckbox-within-hd.html How to use h:selectBooleanCheckBox within h:dataTable? http://www.javabeat.net/tips/43-how-to-use-hselectbooleancheckbox-within-hd.html http://www.javabeat.net/tips/42-fattribute-tag-in-java-server-faces-jsf.html f:attribute Tag in Java Server Faces (JSF) http://www.javabeat.net/tips/42-fattribute-tag-in-java-server-faces-jsf.html http://www.javabeat.net/tips/41-display-error-messages-in-jsf-hmessage-.html Display error messages in JSF [ h:message ] - part 2 http://www.javabeat.net/tips/41-display-error-messages-in-jsf-hmessage-.html http://www.javabeat.net/tips/40-display-error-messages-in-jsf-hmessages-.html Display error messages in JSF [ h:messages ] - part 1 http://www.javabeat.net/tips/40-display-error-messages-in-jsf-hmessages-.html http://www.javabeat.net/tips/39-knowing-about-your-database.html We use the Jdbc APIs for accessing the data from the database system. However, the different databases from different vendors will vary a lot in their underlying model and functionalities. For example, a feature supported in one database might not be supported in another database. So, even before working with a database, it is important to know the supported features and other related information. Java provides an interface called DatabaseMetaData to achieve this. http://www.javabeat.net/tips/39-knowing-about-your-database.html http://www.javabeat.net/tips/38-customizing-dragging-and-dropping-for-swing-c.html Swing's Drop and Drop API can be used for customizing Drag and Drop support. For most of the commonly used components like Text Components, Color Chooser, File Chooser etc, the dropping support is enabled by default. We have to explicitly enable the dragging support by calling the setDragEnabled() method. Before getting into customizing them, let us see a simple example, http://www.javabeat.net/tips/38-customizing-dragging-and-dropping-for-swing-c.html http://www.javabeat.net/tips/37-locking-files-using-java.html File Locking can be achieved in java by making use of the New I/O API (nio). Before the advent of New I/O API, there was no direct support in Java for locking a file. It is important to understand that File locking is hugely dependent on the native operating system on which the program is executing. http://www.javabeat.net/tips/37-locking-files-using-java.html http://www.javabeat.net/tips/36-file-upload-and-download-using-java.html File Upload and Download is always a handy utility to know. There will be some need to upload a file to an FTP server, Like if you generate a report or store some data in .xls file, then it needs to be uploaded to a FTP server for further use. like wise we need to download some data (data stored in .xls files)for manuplation from the server in our projects. Here we have the code to do this for us. The FileUploadDownload utility. http://www.javabeat.net/tips/36-file-upload-and-download-using-java.html http://www.javabeat.net/tips/35-precise-rounding-of-decimals-using-rounding-m.html The Rounding Mode Enum in java.math package is used to perform precise rounding of decimal values. It was introduced in Java 5.0. This Enum provides various constants each of which is used for different modes of rounding. The decimal value would be rounded off to the number of decimal places based on the scale that is defined for the decimal value. http://www.javabeat.net/tips/35-precise-rounding-of-decimals-using-rounding-m.html http://www.javabeat.net/tips/34-using-the-prototype-pattern-to-clone-objects.html Prototype pattern is one of the creational patterns that concentrate on duplicating objects if needed. Assuming that we are in process of creating a template. Most of the times, we copy an existing template, do some changes in it and then will use it. http://www.javabeat.net/tips/34-using-the-prototype-pattern-to-clone-objects.html http://www.javabeat.net/tips/33-sending-mail-from-java.html The Java Mail API provides support for sending and receiving electronic mail messages. The API provides a plug-in architecture where vendor's implementation for their own proprietary protocols can be dynamically discovered and used at the run time. Sun provides a reference implementation and its supports the following protocols namely, http://www.javabeat.net/tips/33-sending-mail-from-java.html http://www.javabeat.net/tips/32-passing-arguments-and-properties-from-command.html Arguments and properties can be passed to a java application from command line. In this techical tip, let us see how to pass arguments as well as properties from command line. http://www.javabeat.net/tips/32-passing-arguments-and-properties-from-command.html http://www.javabeat.net/tips/31-generation-of-random-numbers.html Random numbers in java can be generated either by using the Random class in java.util package or by using the random() method in the Math class in java.lang package. http://www.javabeat.net/tips/31-generation-of-random-numbers.html http://www.javabeat.net/tips/30-downloading-content-from-the-internet.html Let us write a Simple Downloader in this techincal tip by making use of the classes with java.net package. URL stands for Uniform Resource Locator and it is used to locate a resource in the Web in a standard fashion. A resource in the Web can be anything; http://www.javabeat.net/tips/30-downloading-content-from-the-internet.html http://www.javabeat.net/tips/29-creating-user-defined-exceptions.html Though Java provides an extensive set of in-built exceptions, there are cases in which we may need to define our own exceptions in order to handle the various application specific errors that we might encounter. http://www.javabeat.net/tips/29-creating-user-defined-exceptions.html http://www.javabeat.net/tips/28-copying-file-contents-using-filechannel.html In this technical tip, let us see an easy way of achieving file copy using File Channels. File Channels are part of Java New I/O Packages. A file can be viewed as a sequence of bytes. The various Buffer classes in New I/O Packages serve as a container for manipulating the primitive byte contents. http://www.javabeat.net/tips/28-copying-file-contents-using-filechannel.html http://www.javabeat.net/tips/27-logging-messages-using-java-logging-api.html The Logging API in Java enables Applications to log messages of some level which will be very useful for debugging purpose. Say, if a system fails for some reasons, then the reason can be easily traced out by looking at the information available in the log file. In this section, let us see an overview of using Logging facility in Java. http://www.javabeat.net/tips/27-logging-messages-using-java-logging-api.html http://www.javabeat.net/tips/26-working-with-virtual-proxy-pattern.html Application is often a collection of components and in most of the situations it may be the case that a component should be loaded until it is first accessed by the Client. Reasons may be that the component in consideration may be using most of the system resources. For example, http://www.javabeat.net/tips/26-working-with-virtual-proxy-pattern.html http://www.javabeat.net/tips/25-making-use-of-the-properties-class.html In this section, let us make use of the Properties class for storing and loading application related configuration values as well as other user information. It is also possible to query or modify the various System properties using this class. For example, the following code tries to get all the properties that are available for the currently executing JVM. http://www.javabeat.net/tips/25-making-use-of-the-properties-class.html http://www.javabeat.net/tips/24-parsing-input-using-scanner.html A Scanner object can be used to read text input from a number of sources. The input source can be a file, an input stream or even from a string. It internally uses the Regular Expression Api for parsing and getting the input. Let us see a simple example to parse a String object, http://www.javabeat.net/tips/24-parsing-input-using-scanner.html http://www.javabeat.net/tips/23-parsing-xml-documents-using-sax.html Xml Parsers are used to parse and extract information from Xml Documents. The most commonly used Xml Parsers are Simple API for Xml Parsing and Document Object Model. SAX Parsers are preferred when the size of the Xml Document is comparatively large and the application doesn't wish to store and reuse the Xml information in the future. In this tip, let us see how to parse an Xml Document using SAX Technique. http://www.javabeat.net/tips/23-parsing-xml-documents-using-sax.html http://www.javabeat.net/tips/22-persisting-object-state-in-xml-format.html Persistence is the process of saving the state of an object permanently to a storage like file or database, and the state of the object can be restored at a later time. In Java terms, Persistence is nothing but Serialization. For example, the following code is used to save the state of an object in a file. http://www.javabeat.net/tips/22-persisting-object-state-in-xml-format.html http://www.javabeat.net/tips/21-randomly-accessing-the-file-contents.html In this techincal tip, let us see how to access the contents of a file randomly instead of the traditional sequential access. Imagine that we want to search for a particular record in a file. If we prefer Sequential access in this case, then it will involve traversing over the file byte by byte and searching for the relevant record. This won't be an ideal solution particularly if the size of the file is too big. http://www.javabeat.net/tips/21-randomly-accessing-the-file-contents.html http://www.javabeat.net/tips/20-sorting-custom-types-in-java.html The class java.util.Collections provides many Utility methods for simplifying the most commonly used operations. One of the methods available in that class is sort() which is used for sorting elements. Let us the see how the Collections.sort() method operates on pre-defined data-types as well as user-defined data-types. http://www.javabeat.net/tips/20-sorting-custom-types-in-java.html http://www.javabeat.net/tips/19-recursively-traversing-files-and-folders-usin.html In this section, let us see how to recursively traverse over files and folders by making use of Java File API. Whether it is a folder or a file, both are represented as a java.io.File object. For example, consider the following code snippet, http://www.javabeat.net/tips/19-recursively-traversing-files-and-folders-usin.html http://www.javabeat.net/tips/18-factory-pattern-design-patterns-in-javaj.html Creational pattern deals with the creation of objects and it hides the complex logic involved in the object creation object from the clients. One of the common creational patterns is the Factory pattern and it is used extensively in Applications. Let us understand what factors should be considered in mind while designing a Factory pattern or a Factory method pattern. http://www.javabeat.net/tips/18-factory-pattern-design-patterns-in-javaj.html http://www.javabeat.net/tips/17-conversion-between-array-and-list-types.html In some cases, we may need to convert an array to a list or vice versa. The method asList() is available in the Arrays class, and the toArray() method in list and set classes serve this purpose. http://www.javabeat.net/tips/17-conversion-between-array-and-list-types.html http://www.javabeat.net/tips/16-querying-class-information-at-runtime-using-j.html Java Reflection API provides support for querying information about a class at run-time. This information includes the list of public as well as private members (methods) available for the class, the various public operations it supports etc. This section will guide you in making use of the Reflection API. http://www.javabeat.net/tips/16-querying-class-information-at-runtime-using-j.html http://www.javabeat.net/tips/15-using-the-jar-utility.html Jar stands for Java Archive file and it is used to compress and archive one or more files. It is equivalent to Zip file in Window operating system. A typical jar file contains Java class files in addition to source files as well as resource files, like images and properties. http://www.javabeat.net/tips/15-using-the-jar-utility.html http://www.javabeat.net/tips/14-storing-application-data-using-preferences-ap.html Applications can now make use of the Java Preferences API for storing and retrieving Application related data. The location where the Data gets stored is implementation specific. Two levels of Preferences come into picture, one is the User Preferences for storing user information and the other is the System Preferences that deals with information common to all users as well as configuration details. http://www.javabeat.net/tips/14-storing-application-data-using-preferences-ap.html http://www.javabeat.net/tips/13-threads-synchronization.html Synchronization is done in order to protect a segment of code from being accessed by more than a single Thread at any particular instance of time. In Java, synchronization is achieved with the use of synchronized keyword. Synchronization can be applied to methods as well as to a block of code. http://www.javabeat.net/tips/13-threads-synchronization.html http://www.javabeat.net/tips/12-overriding-the-tostring-method-in-object-cl.html The toString() method in the Object class is used to display some information regarding any object. If any code needs some information of an object of a class, then it can get it by using this method http://www.javabeat.net/tips/12-overriding-the-tostring-method-in-object-cl.html http://www.javabeat.net/tips/11-using-the-externalizable-interface.html Serialization is the process of giving persistence storage to Java objects so that they can be restored at a later time. Classes can be made persistent in Java by implementing the Serializable interface. Serializable is a marker interface meaning that it has no methods within it. Any Serializable class can be passed on to ObjectOutputStream.writeObject(object) for saving the object state and a call back to ObjectInputStream.readObject() will get the object back from the storage. http://www.javabeat.net/tips/11-using-the-externalizable-interface.html http://www.javabeat.net/tips/10-enhanced-for-loop-for-user-defined-objects.html Enhanced For-loop is a new syntax for traversing over a collection of objects and it was introduced from Java 5.0. Let us see how Enhanced for-loop operates on user-defined Objects. The following example shows the syntax of using enhanced for-loop on a Collection object, http://www.javabeat.net/tips/10-enhanced-for-loop-for-user-defined-objects.html http://www.javabeat.net/tips/9-hashcode-and-equals-methods.html HashTable, HashMap and HashSet are the Collection classes in java.util package that make use of hashing algorithm to store objects. In all these Collection classes except HashSet, objects are stored as key-value pairs. For the storage and the retrieval of any user-defined objects it is a good practice to override the following methods which is mentioned below, http://www.javabeat.net/tips/9-hashcode-and-equals-methods.html http://www.javabeat.net/tips/8-using-the-new-process-builder-class.html We all know how to execute programs from within a Java Application by making use of the Runtime Api. For example, assume that we want to launch the Internet Explorer browser within the Java code. Then the following code snippet will just do that, http://www.javabeat.net/tips/8-using-the-new-process-builder-class.html http://www.javabeat.net/tips/7-singleton-pattern-design-patterns-in-javaj.html Situations often will demand for the existence of only one object for a particular class in an Application. For example, the existence of only one Database Connection for a particular session, one object referencing the set of Global properties being shared across the various modules, etc. http://www.javabeat.net/tips/7-singleton-pattern-design-patterns-in-javaj.html http://www.javabeat.net/tips/6-template-method-pattern-design-patterns-in.html A Template method pattern provides a skeleton for performing any sort of algorithm or an operation, and it allows the sub-classes to re-define part of the logic. Let us directly get into an example to clarify things in a much better manner. For example, if we wish to write a String Decorator class, http://www.javabeat.net/tips/6-template-method-pattern-design-patterns-in.html http://www.javabeat.net/tips/5-state-pattern-design-patterns-in-javaj2ee.html State pattern falls under the category of Behavioural patterns. Assume that we have an object and its behavior is largely dependent on the state of its internal variables. Consider the following example, http://www.javabeat.net/tips/5-state-pattern-design-patterns-in-javaj2ee.html http://www.javabeat.net/tips/4-expression-language-in-jsp-20.html Expression Language was first introduced in JSTL 1.0 (JSP Standard Tag Library ). Before the introduction of JSTL, scriptlets were used to manipulate application data.JSTL introduced the concept of an expression language (EL) which simplified the page development by providing standerd tag libraries. These tag libraries provide support for common, structural tasks, such as: iteration and conditionals, processing XML documents, internationalization and database access using the Structured Query Language (SQL). The Expression Language introduced in JSTL 1.0 is now incorporated in JavaServer Pages specification(JSP 2.0). This articie gives some idea about what is Expression Language and how to simplify the maintenance for JSP applications by avoiding scripting elements. http://www.javabeat.net/tips/4-expression-language-in-jsp-20.html