J2EE Application Deployment Roles

The J2EE platform promotes a sequential and modular mechanism for the deployment of its applications. There are a series of steps, which are conducted by specific roles (also known as providers ), in the deployment of J2EE applications, as depicted in Figure 1.5, and described as follows .

J2EE Product Provider

The J2EE product providers are companies, such BEA Systems, IBM, and Sun Microsystems, which implement the J2EE platform according to the J2EE Specification within their products (operating systems, database systems, application servers, or Web servers).

J2EE Tool Provider

A tool provider provides tools for the development, assembly, packaging, and deployment of J2EE components and applications. Such providers include BEA Systems, TogetherSoft, WebGain, and Borland.

Note

A product provider will in most cases provide tools for the deployment of applications into their application server environments. In such cases, they are also considered to be tool providers as well.

Application Component Provider

The application component provider is either a J2EE Web or business component developer who creates Web components, enterprise beans, applets, or application clients for use in J2EE applications. One of the goals of the J2EE Application Programming Model is to ensure that the infrastructure services required by J2EE components, such as security, database access, and transaction management, are not the focal point of the J2EE component developers, whose role is primarily to implement the business logic into J2EE components (servlets, JSPs, and EJBs).

J2EE achieves this by transferring these service responsibilities on to the J2EE platform, which provides a way to specify them through XML-based declarations that are stored within deployment descriptors ( .xml files). These deployment descriptors are completely separate from the component code, and enable a J2EE application to be modified without having to modify any of its associated components.

The first step in the J2EE application deployment process is for the J2EE client, Web, and server component developers to package their components that will form the J2EE application into modules of similar component types:

• Client components are all compiled, and the .class files with a deployment descriptor ( application.xml file) are then packaged to form the Java Module ( .JAR file).

• Web components are all compiled, and the .class , .jsp , .html , and .gif files with a deployment descriptor ( Web.xml file) are then packaged to form the Web Module ( .WAR file).

• Server components (EJBs) are all compiled, and the .class files with a deployment descriptor ( ejb-jar.xml file) are then packaged to form the EJB Module ( .JAR file).

Application Assembler

The application assembler's role is to receive the application component modules ( .JAR and .WAR files) from the component providers and assemble them into one Enterprise Archive (EAR) file.

Application Deployer

Through the use of tools provided by a product provider, the role of the application deployer is to deploy the J2EE application into the context of a J2EE-compliant application server, such as the BEA WebLogic Server 7.0. In order to deploy a J2EE application, the deployer will adhere to the following three-step deployment process:

• Installation ” The deployer moves the application components to the server machine, and generates the additional container-specific classes and interfaces that assist the containers in managing the application components at runtime.

• Configuration ” Validates and modifies the deployment descriptor of the J2EE application supplied by the application component providers, in order to resolve any external dependencies, implement security settings, and set any transaction attributes.

• Execution ” The deployer starts the J2EE application.

System Administrator

The role of the system administrator is to maintain and administer the J2EE application server environment once the J2EE application has been deployed. Ideally, the system administrator should be using tools certified by the product provider of the application server for any maintenance and monitoring operations.