J2EE application deployment (2 ):

1. Configure the J2EE package
1.1 enterprise application development process
1.2 Structure of J2EE application package
1.3 EAR deployment descriptor
2. A simple instance
2.1 Components
2.2 Assembly application
2.3 deploy and run applications
3. Optional application deployment descriptor tag
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1. Configure the J2EE package
In the previous article, we learned some basic knowledge about J2EE application encapsulation and deployment, including the different roles and behaviors of the class loader. Next, you can configure and deploy enterprise applications. Therefore, we must understand the process of creating the EAR file and the content of the application deployment descriptor.
1.1 enterprise application development process
The process of constructing an enterprise application can be summarized as follows:
Construct various components, including EJBs, JSP pages, servlets, and resource adapters.
Package these components into a J2EE module in the JAR file format, and provide a deployment descriptor for the J2EE module. A J2EE module is a collection of one or more J2EE components of the same type. That is to say, an EJB module can contain more than one EJB, A Web application module can contain multiple JSP pages and servlets, and a resource adapter package can contain multiple resource adapters.
Create an EAR file with one or more J2EE modules, and provide the enterprise application deployment descriptor to construct a J2EE application. The simplest J2EE application only contains one J2EE module. A slightly more complex J2EE application can consist of multiple J2EE modules, A more complex J2EE application can contain multiple J2EE modules and dependent libraries used by classes in the modules. The J2EE application can also contain help files and other documents describing the deployment process.
Deploy the J2EE application on the J2EE platform. Install the J2EE application and integrate it with the infrastructure provided by the application server. During the deployment of J2EE applications, each J2EE module is deployed separately according to the deployment requirements of such modules, and each component is deployed to a suitable container suitable for this component type. For example, suppose there is a my. ear file that contains my. jar and my. war. When you deploy an application. the ear file is copied to the application server. Then, the deployment mechanism of the application server extracts my. jar and my. war module, which is deployed according to the class loading requirements of the current platform. If both modules are successfully deployed, the entire J2EE application is successfully deployed.
The J2EE enterprise application development and deployment process can be illustrated as follows:
When a component is encapsulated as a J2EE module, a deployment descriptor is provided. The J2EE module can be created using a deployment tool. The deployment tool can also be used to deploy and "deploy" independent J2EE modules to encapsulate one or more J2EE modules and other deployment descriptors into J2EE applications, it is used to add additional content to a J2EE application, delete some content from a J2EE application, or deploy the entire application on the application server.