EJB core technology and its application

Introduction of EJB Technology

The full name of the EJB is the Enterprise Java Bean. Is the commercial application component technology in Java. The role EJB component structure in EJB structure is a distributed computing structure based on component, and it is a component in Distributed Application System.

A complete EJB based distributed computing structure consists of six roles, which can be provided by different developers, and each role must follow the EJB specification provided by Sun to ensure compatibility with each other. These six roles are EJB component developers (Enterprise Bean Provider), application group (application assembler), Deployer (deployer), EJB server provider (EJB server-based Provider ), EJB container provider (EJB Container Provider), system administrator:

Analysis of each role in EJB

1, EJB Component Developer (Enterprise Bean Provider)

EJB component developers are responsible for developing EJB components that execute business logic rules, and the developed EJB components are packaged into Ejb-jar files. The EJB component developer is responsible for defining the remote and home interfaces of the EJB, writing the EJB class that executes the business logic, and providing the deployment file (deployment descriptor) to deploy the EJB. The deployment file contains the name of the EJB, the resource configuration used by the EJB, such as JDBC. The EJB component developer is a typical business application development domain expert.

EJB component developers do not need to be proficient in system-level programming, so there is no need to know some system-level processing details, such as transactions, synchronization, security, distributed computing, and so on.

2, application combination (application assembler)

The application portfolio is responsible for using a variety of EJB combinations for a complete application system. Application groups sometimes need to provide some relevant programs, such as in an E-commerce system, the application group needs to provide JSP (Java Server Page) program.

The application group must master the home and remote interfaces of the EJB used, but do not need to know the implementation of these interfaces.

3. Deployer (Deployer)

The deployer is responsible for deploying the Ejb-jar file into the user's system environment. The system environment contains some kind of EJB server and EJB Container. The deployer must ensure that all resources declared by the EJB component developer in the deployment file are available, for example, that the Deployer must configure the database resources required for the EJB.

The deployment process is two-step: The Deployer first uses the tools provided by EJB container to generate classes and interfaces that enable EJB container to leverage these classes and interfaces to manage EJBS in the running state. The Deployer installs the EJB components and other classes generated in the previous step into the EJB container. A deployer is an expert in an EJB running environment.

In some cases, the deployer also needs to understand the business methods that the EJB contains in order to write some simple program tests once the deployment is complete.

4. EJB Server Provider (EJB server-based Provider)

The EJB server provider is an expert in the system domain, proficient in Distributed transaction management, distributed object management, and other system-level services. EJB server providers are typically provided by operating system developers, middleware developers, or database developers.

In the current EJB specification, assuming that the EJB server provider and the EJB container provider are from the same developer, there is no interface standard defined between the EJB server provider and the EJB container provider.

5. EJB container provider (EJB Container Provider)

The EJB container provider provides the following features:

Provides an EJB deployment tool to provide a running environment for deployed EJB components. EJB Container is responsible for providing transaction management, security management and other services for EJB.

The EJB container provider must be a system-level programming expert and experience in a number of areas of application. The work of the EJB container provider focuses on developing a scalable container with transaction management capabilities integrated into the EJB server. The EJB container provider provides a standard set of Easy-to-use APIs for EJB component developers to access the EJB container so that EJB component developers do not need to know the various technical details in the EJB server.

The EJB container provider is responsible for providing a system monitoring tool for real-time monitoring of the EJB container and the state of the EJB component running in the container.

6, systems Administrator (System administrators)

The system administrator is responsible for providing an enterprise-level computing and network environment for EJB servers and containers.

The system administrator is responsible for monitoring the performance of EJB components using the monitoring management tools provided by the EJB server and container.