EJB technology and application

1. Introduction to EJB technology
The full name of EJB is Enterprise java bean. Is the commercial application component technology in JAVA. The role EJB component structure in the EJB structure is a distributed computing structure based on components and a component in a distributed application system.
A complete EJB-based distributed computing structure consists of six roles, which can be provided by different developers. Each role must follow the EJB specifications provided by Sun, to ensure compatibility between them. These six roles are EJB component developer (Enterprise Bean Provider), Application aggreger (Application aggreger), Deployer (Deployer), and EJB Server Provider (EJB Server Provider), EJB Container Provider, System Administrator ):
2. Analysis of each role in EJB
1. Enterprise Bean Provider)
The EJB component developer is responsible for developing the EJB component that executes the commercial logic rules, and developing the EJB component to package it into the ejb-jar file. The EJB component developer is responsible for defining the remote and home interfaces of EJBs, compiling the EJB class that executes the commercial logic, and providing the deployment descriptor ). The deployment file contains the EJB name and the resource configuration used by the EJB, such as JDBC. EJB component developers are typical experts in commercial application development.
EJB component developers do not need to be proficient in system-level programming. Therefore, they do not need to know system-level processing details, such as transactions, synchronization, security, and distributed computing.
2. Application aggreger)
The application composite is responsible for combining a complete application system using various EJBs. Application composite sometimes needs to provide related programs. For example, in an e-commerce system, the application composite needs to provide JSP (Java Server Page) programs.
The application composite must master the home and remote interfaces of the EJB used, but do not need to know the implementation of these interfaces.
3. Deployer)
The deployer is responsible for deploying the ejb-jar file to the user's system environment. The system environment contains an EJB Server and an EJB Container. The deployer must ensure that all resources declared by the EJB component developer in the deployment file are available. For example, the deployer must configure the database resources required by the EJB.
The deployment process is divided into two steps: the deployer first uses the tools provided by the EJB Container to generate some classes and interfaces so that the EJB Container can use these classes and interfaces to manage EJBs in the running state.
The deployer installs the EJB component and other classes generated in the previous step into the ejb iner.
The deployer is an expert in an EJB running environment.
In some cases, the deployer also needs to understand the business methods contained in the EJB during deployment so as to write some simple program tests after the deployment is complete.
4. EJB Server Provider)
The EJB server provider is an expert in the system field and is proficient in distributed transaction management, distributed object management, and other system-level services. EJB server providers are generally provided by operating system developers, middleware developers, or database developers.