Java EE Overview (4)

The Java EE component is packaged separately and bundled into a Java EE application for deployment. Each component, its related files such as GIF, HTML files, and server-side feature classes, and a deployment description, form a module and are added to the Java EE application. A Java EE application consists of one or several enterprise Bean component modules, Web Component modules, or application client component modules. Depending on the design requirements, the final enterprise solution can be a Java EE application, or it can be composed of two or more Java EE applications.
A Java EE application and each of its modules has its own deployment instructions. A deployment description is an XML file with an. xml extension that describes the deployment settings for a component. For example, a description of the deployment of a enterprise bean module describes the transaction attributes and security authorization of a enterprise bean. Because the deployment description information is public, it can be changed without having to modify the bean's source code. At runtime, the Java server will read this deployment description and follow it.
A Java EE application and all of its modules are submitted to a enterprise ARchive (EAR) file. An ear file is a standard Java Archive (JAR) file with an. ear extension. In the GUI version of the Java SDK Application Deployment tool, you first create an ear file and add jar files and Web Archive (WAR) files to it. However, if you are using a command-line packaging tool, you must first create the jar and war file, but the ear file is built. For more information on the Java EE SDK tools, see the tools.

1. Each EJB jar file contains a deployment description, Enterprise bean file, and related files.
2. Each application client jar file contains a deployment description, a class file for the application client, and related files.
3. Each war file contains a deployment description, a Web Component file, and related resources.

The use of modules and ear files makes it possible to use the same component to assemble many different Java-EE applications. No extra programming work, all you have to do is add a variety of Java EE modules to the Java EE ear file.

8. Developing role-reusable modules makes it possible to divide the development process and deployment process of the application into different roles. In this way, different people or companies can undertake different tasks in each part of the process.
The first two roles assume the task of purchasing and installing Java EE products and tools. After the software has been purchased and installed, the application component provider begins to develop the Java EE component, where the application assembler is responsible for the assembly, and the application Deployer is responsible for deployment. In a large organization, each of these roles may correspond to different individuals and groups. This division of work is done because the previous role will output a portable file, which will be the input of the latter role. For example, in the application Component provider phase, an enterprise bean software developer submits an EJB jar file. In the application assembler phase, other developers combine the EJB jar files into a Java EE application and save it as an ear file. At the application Deployer stage, the system administrator of the consumer site uses the ear file to install the Java application to the Java server.
Different roles do not necessarily have to be performed by different people. For example, if you are working in a small company or you are engaged in prototype development of a sample program, you may also need to perform each phase of the task.

9, Java EE product provider Java products Provider is designed and provided to achieve the Java EE specification defined Java platform, API and other functions of the company. This generally refers to the operating system, database systems, application servers, or Web server vendors, they follow the Java EE specifications to achieve the Java platform.

9.1 Tool Provider tool providers are companies or individuals that establish the development, assembly, and packaging tools used by component providers, assemblers, and Deployer. For more information about Java EE SDK 1.3 available tools, see tools.

9.2 Application Component Provider application component providers are companies or individuals that create Web components, enterprise beans, applets, or application clients used by Java EE applications.

The 9.3 Enterprise Bean Developer Application Assembler is a company or person who accepts an application component jar file from the component provider and assembles it into a Java EE application ear file. The assembler or deployer can edit the deployment instructions directly or use tools that can correctly add XML flags based on interactivity. A software developer performs the following tasks and submits an ear file containing the Java EE application:

1. Assemble the EJB jar files and war files that were built in the previous phase into a Java EE application (EAR) file.
2, detailed description of the application of Java EE deployment instructions.
3. Verify that the components in the ear file comply with the Java EE specification.