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J2EE application author: Unknown J2EE applications
Assessing J2EE applications from the following three modules: Enterprise Beans, Web Components, and J2EE Applications Clients. These modules are reusable, and you create a new application from existing Enterprise Beans and Components. And, due to the might of these modules, the application they consisted will be able to run any J2EE server that meets the specification.
J2EE application content
Figure 1-4 shows the inheritance relationship of the J2EE application. A J2EE application may contain one or more Enterprise Beans, Web Components, or J2EE application client components. An Enterprise Bean consists of three class files, EJB Class, Remote Interface, and HOME interface. (The next chapter will discuss these class files in detail) .Web Components can include the following file types: Servlet Class, JSP, HTML, GIF.J2EE application customers are running in a environment (container) that can be allowed to access J2EE service Java app.
Each J2EE application, Web Component, Enterprise Bean has a distribution description (DEPLOY DEPLOY Descriptor). A distribution description is a .xml file that describes the component. For example, the EJB distribution describes the transaction characteristics and security certification declared Enterprise Bean. Because this information is declared, it can be changed without changing the source code of the bean. When running, J2EE reads this information and step by step.
Figure 1-4 Content of J2EE Application
J2EE uses a special file format to bundle each module, bundle the J2EE application with .ser file, use .jar bundle Enterprise Bean. For example, one .ear file contains a .xml file as its distribution description, or one or more ejb.jar and .war files. An ejb.jar contains its distribution description, and a .class file as an Enterprise Bean, the following table lists each file type in the J2EE application:
Table 1-2 J2EE file use
Element file type
J2EE application. Pear
J2EE application distribution description. Xml
Enterprise bean ejb.jar
EJB distribution description. Xml
EJB Class .Class
Remote interface .CLASS
HOME interface .CLASS
Web component .war
Web Component distribution description .xmljsp file .jsp
Servlet Class .class
GIF file .gif
HTML file .html
J2EE application customer .jar
J2EE application customer distribution description. Xml
Java app .class
J2EE application development phase
The development of J2EE applications has the following stages
Enterprise Bean creation
Web Component creation
J2EE application assembly
J2EE application distribution
In a large tissue, each link may have a different group or individual responsibility. This manual allocation is due to a light output file to the next phase of each previous stage. For example, in the generation phase of Enterprise Bean, developers distribute EJB.jar files. In the J2EE application phase, another developer connects these ejb.jar files with the J2EE application and stores as .ser files. In the final phase, the J2EE application distribution phase, the client's system administrator uses the .ser file to install the J2EE application to the J2EE server. Figure 1-5 shows the last two phases.
Different stages are not always performed by different people. For example, if you are a small company, or your own routine, you can do every stage yourself.
Figure 1-5 Assembly and distribution of J2EE applications
The following sections summarize the development phase of the J2EE application. Because the J2EE application does not need each type of module, only the top three are required. The last step is necessary. Since we focus on Enterprise Beans, do not discuss the creation phase of Web Component. The next chapter of the manual, Getting Started will give you a J2EE application that contains Enterprise Beans.
Enterprise bean creation phase
Personnel: Software Developer
task:
* Writing and compiling the Java source code required for Enterprise Bean
* Specification Enterprise BEAN's distribution description
* Generate .class files and distribution descriptions to ejb.jar files
Published file: Ejbl.jar file containing Enterprise Bean
Web Component Creation Stage
Personnel: Network Designer (JSP Component), Software Developer (Servlets)
task:
* Written and compile the source code for servlet
* Written .jsp and .html file
* Bundle .class, .jsp, .html and distribution description to .war files
Published file: contains a WEB Component .war file
J2EE application's client creation
Personnel: Software Developer
task:
* Written and compile the necessary Java source code required
* Specification client distribution description
* Bundle .class files and distributions describe the .jar files as the client
Published file: Contains a .jar file with the J2EE application client.
J2EE application assembly
Personnel: Software Developer
task:
* Assemble the Enterpise Bean file (ejb.jar) and web component (.war) file to J2EE application file (.ear)
* Specification J2EE application distribution specification
Published file: contains a .ser file containing J2EE applications.
J2EE application distribution
Personnel: System Administrator
task:
* Add J2EE application file (.ear) to the J2EE server during the addition.
* Configure the optional Environment Variables of the J2EE application by modifying the profile of the J2EE application to arrange the J2EE application J2EE application to the server