Unveil J2EE and unveil J2EE

Unveil J2EE and unveil J2EE
For beginners who first started learning java, they should first know the java version. java has introduced three versions: J2SE, J2EE, and J2SE, which contain the original core class library. J2EE features are comprehensive and used for data processing and server-side applications. It is mainly used for embedded devices such as mobile phones. The following describes J2EE in detail.
The core of J2EE is a set of technical specifications and guidelines. The components, service architecture, and technical layers contained in the Guidelines share common standards and specifications, allowing various platforms that follow the J2EE architecture, there is good compatibility to solve the problem of incompatibility between the information products used by the enterprise backend in the past and the difficulty of intercommunication between the enterprise and the outside.

The difference between the J2EE component and the "standard" Java class is that it is assembled in a J2EE application and has a fixed format and complies with the J2EE specifications, and is managed by the J2EE server. The J2EE specification defines J2EE components as follows: the client application and applet are components running on the client; Java Servlet and Java Server Pages (JSP) are Web components running on the Server; the Enterprise Java Bean (EJB) component is a service component running on the server.

Advantages:
1. simplified structure
The J2EE platform supports simplified and component-based development models. Because J2EE is based on the Java programming language and J2SE platform, it provides the portability of writing once and running anywhere, all servers that comply with the J2EE standard support this model.
2. Improve development efficiency
Due to the use of component technologies, developers can divide application development into different parts based on their skills, develop applications in parallel, and provide overall development efficiency.
3. High portability
In addition to the inherent portability of the Java language, the EJB architecture provides a standardized application programming interface between the Bean and the container that supports the Bean, this allows developers to port beans from one operating environment to another without re-writing their source code.
4. reusability, good scalability, and easy maintenance
In the EJB model, each software component is strictly separated. Therefore, you can assemble the existing software component into a server application. Applications based on the J2EE platform can be deployed on various operating systems. As components can be updated and replaced independently, new functions can be easily added by updating specific components in the application.
5. Retain existing IT assets
Because enterprises must adapt to new business needs and make full use of existing enterprise information system investment, rather than re-developing, it is particularly important to update the overall solution, A server platform built on an existing system in a progressive (rather than radical, totally negative) manner is what most companies want.