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This article mainly explains "what are the roles in EJB". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let the editor take you to learn "what roles are there in EJB"?

I. brief introduction of EJB technology

The full name of EJB is Enterprise java bean. Is a commercial application component technology in JAVA. The role EJB component structure in EJB structure is a component-based distributed computing structure, which is a component in distributed application system.

A complete EJB-based distributed computing architecture consists of six roles, which can be provided by different developers. The work done by each role must follow the EJB specification provided by Sun to ensure the compatibility between them.

These six roles are EJB component developer (Enterprise Bean Provider), application composer (Application Assembler), deployer (Deployer), EJB server provider (EJB Server Provider), EJB container provider (EJB Container Provider), and system administrator (System Administrator).

Second, the analysis of each role in EJB

1. EJB component developer (Enterprise Bean Provider)

EJB component developers are responsible for developing EJB components that implement 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 performs the business logic, and providing the deployment file (deployment descriptor) for deploying the EJB.

The deployment file contains the name of EJB, the resource configuration used by EJB, such as JDBC, and so on. EJB component developers are typical experts in the field of business application development.

EJB component developers do not need to be proficient in system-level programming, so they do not need to know some system-level processing details, such as transactions, synchronization, security, distributed computing and so on.

2. Application Combinator (Application Assembler)

The application composer is responsible for assembling a complete application system using various EJB. Application composers sometimes need to provide some related programs, such as in an e-commerce system, application combiners need to provide JSP (Java Server Page) programs. The application composer 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 to 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, the deployer must configure the database resources required by EJB.

The deployment process is divided into two steps: the deployer first uses the tools provided by EJB Container to generate classes and interfaces that enable EJB Container to use these classes and interfaces to manage EJB in a running state. The deployer installs the EJB component and other classes generated in the previous step into EJB Container. The deployer is an expert in an EJB runtime environment.

In some cases, deployers also need to understand the business methods included in EJB at deployment time so that they can write some simple program tests after deployment is complete.

4. EJB server provider (EJB Server Provider)

EJB server providers are system experts who are 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.

In the current EJB specification, it is assumed that the EJB server provider and the EJB container provider come from the same vendor, so there is no interface standard between the EJB server provider and the EJB container provider.

5. EJB Container provider (EJB Container Provider)

The EJB container provider provides the following functions:

Provide EJB deployment tools to provide a running environment for deployed EJB components. EJB container is responsible for providing transaction management, security management and other services for EJB.

EJB container providers must be system-level programming experts and have some experience in the application domain. The work of the EJB container provider is focused on developing a scalable container with transaction management capabilities integrated into the EJB server.

The EJB container provider provides a set of standard and easy-to-use API access EJB containers for EJB component developers, so that EJB component developers do not need to know the technical details of the EJB server. The EJB container provider is responsible for providing system monitoring tools to monitor the status of the EJB container and EJB components running in the container in real time.

6. System administrator (System Administrator)

The system administrator is responsible for providing an enterprise-class computing and network environment for EJB servers and containers. The system administrator is responsible for monitoring the operation of EJB components by using the monitoring and management tools provided by EJB servers and containers.

At this point, I believe you have a deeper understanding of "what roles are in EJB". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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