13.4.1 Overview of the exploded archive format

This chapter provides an overview of the exploded archive format and describes how to deploy and un-deploy the exploded archive-format J2EE applications.

Organization of this subsection
(1) Exploded archive-format J2EE applications

(1) Exploded archive-format J2EE applications

An exploded archive-format J2EE application is one of the application formats that can be executed on a J2EE server. An exploded archive-format J2EE application holds the application entities, such as the EJBs and servlets, in files or directories that are outside the J2EE server and follow fixed rules. If you create a root directory called an application directory and store the components, such as the EJB-JAR and Web applications, in the application directory, you can operate the application as a J2EE application. For details on the application directory, see 13.4.2 Configuration of the application directory.

The following figure shows an exploded archive-format J2EE application.

Figure 13-2 Exploded archive-format J2EE application

[Figure]

An exploded archive-format J2EE application stores the path information to the DD and the application directory. The components, such as the EJB-JAR or Web applications, are not stored in the working directory of the J2EE server.

This subsection describes the features of an exploded archive-format J2EE application.

(a) Simplifying the replacement of a J2EE application

With an exploded archive-format J2EE application, you need not archive the components in the EAR format. Therefore, you can replace an exploded archive-format J2EE application using fewer steps as compared to an archive-format J2EE application.

Moreover, by using the reload functionality, you dynamically replace a J2EE application using even fewer steps. The reload functionality detects the updates of the files configuring the J2EE application and reloads the updated J2EE application. By using the reload functionality, you dynamically replace the deployed servlets, JSPs, and EJB-JARs without restarting the J2EE server. For details on the reload functionality, see 13.8 Detecting updates and reloading J2EE applications.

(b) Sharing the application directory across multiple J2EE servers

With the exploded archive-format J2EE applications, multiple J2EE servers can share the application directory.

For example, when you use an archive-format J2EE application, if you want to execute the J2EE applications with the same contents on multiple J2EE servers, you must allocate an EAR file or a ZIP file on multiple J2EE servers respectively. Also, to replace an imported J2EE application, you must re-import and redeploy the J2EE application for all those servers.

However, with the exploded archive-format J2EE applications, only the path information to the DD and the application directory is stored, so multiple J2EE servers can share the components, such as the EJB-JAR or Web applications, existing in the application directory.

For example, when J2EE servers are arranged in a cluster configuration and the same J2EE application is to be used on each J2EE server, you can specify the same directory as the application directory. The same application directory is referenced, so if any change occurs in the J2EE application, you can replace all J2EE applications by merely updating the files, such as the class files, in the application directory. The following figure shows an example of sharing an application directory.

Figure 13-3 Example of sharing an application directory

[Figure]

Note that when a J2EE application is shared, place the application directory in an environment (such as a shared disk device) that can be referenced from each J2EE server.