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Enterprise applications

An enterprise application project contains the hierarchy of resources that are required to deploy an enterprise (Java EE) application to WebSphere Application Server. It can contain a combination of Web applications (WAR files), EJB modules, Java libraries, and application client modules (all stored in JAR format). They also must include a deployment descriptor (applicaton.xml within the META-INF directory), which contains meta information to guide the installation and execution of the application.

The JAR files within an enterprise application can be used by the other contained modules. This allows sharing of code at the application level by multiple Web or EJB modules.

On deployment, the EAR file is unwrapped by the application server and the individual components (EJB modules, WAR files, and associated JAR files) are deployed individually, however, some aspects are configured across the enterprise application as a whole including, for example, shared JAR files.

The use of EJBs is not compulsory within an enterprise application. When developing an enterprise application (or even a Web application), the developer can write whatever Java is most appropriate for the situation. EJBs are the defined standard within Java EE for implementing application logic, but many factors can determine the decision for implementing this part of a solution. In the RedBank sample application presented later in this chapter, the business logic is implemented using standard Java classes that use HashMaps to store data.

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