Java EE Technology __java

Maybe you've been learning Java for so long, but if someone asks you what is a Java EE. How would you answer him? Let me talk about Java EE related technology. (Personal opinion only)

When we talk about Java EE, we first take a look at the platform. Currently, there are 3 versions of the Java platform: javame (Java Platform Micro Edition,java miniature) for small devices and smart cards, javase for desktop systems (Java Platform Standard Edition , Java Standard Edition) and Java Java Platform Enterprise Edition, which is suitable for enterprise-class applications. Java EE is a development of enterprise-class application of the norms and standards, in the current enterprise-level development is most commonly used, the most favored by developers.

Java EE applications are made up of components, which means that they are based on component development. Components are self-contained units that are assembled into Java EE applications through related classes and files and interact with other components. Changes to one component do not affect other components, code duplication is reduced, and reuse rates are high. is advantageous to the good division of labor and the cooperation, realizes the parallel development. If it is developed with a three-tier structure, then the presentation layer and the data access layer are independent, so the art can be more convenient to expand the presentation layer, so that the system has good scalability.

In the Java EE Technology System, a variety of framework technologies are also integrated. Among them, the SSH (struts+hibernate+spring) framework technology is the most famous, these framework technology represents the current enterprise (company) level development trend. Of course, there are some more well-known framework technology, such as: WebWork, JSF, EJB, Ibats and so on. Various framework technologies are formed on the basis of Java EE, and applications are created in the framework technology. Therefore, if you want to learn Java EE, you must first learn Java EE based on servlet technology. If an introduction to learn SSH framework technology to build, as if a person is still an hour to learn to walk first, not first learn to climb, which is somewhat spot "taste."

The technical architecture of Java EE also embodies the principle of layering, similar to the C # three-tier structure. Only the "Change", the form has changed, the core of the technical content has not changed. When we design a system, we usually design the system into layers (usually three layers). What are the benefits of designing a three-storey? Because any software or system, there are about 80% of the time is in the late maintenance stage, designed into three layers, conducive to future maintenance and expansion, but also conducive to the control of the program and the display of the page.

The technical structure of Java EE is divided into three layers, so what are the three layers? In fact, similar to C #, respectively, is the presentation layer, middle tier, data layer. C # Three layers are the presentation layer, the business logic layer, the data access layer, but not the same argument, but the expression is the same meaning just. The presentation layer is the user interface, the middle tier contains various business logic, and the data layer is the access and encapsulation of the data. In these three layers, which layer do you think is the most important? Maybe you think the business logic layer, but the answer is wrong, the correct answer is the presentation layer. Just imagine, you make a web system, the interface is not beautiful, unfriendly, users do not want to use, that also talk about what business logic AH. So here I recommend you, in the three-tier structure to develop a project, first from the presentation layer, first the presentation layer well. Then one analyzes the business logic, and then the idea of data access is there. Oh......

What is the content of the Java EE technology that has been said for so long? What technology is used to achieve each layer. Let me start with the presentation layer.

The presentation layer technique is to use HTML tags, javascript scripts, and Ajax in JSP pages. It should be noted that Ajax is not a technology, but a combination of several technologies. It takes the form of an asynchronous request, with the primary function of sending a request to the server, processing the data, or displaying the page again based on the returned data.

Middle-tier technology is mainly JSP, Servlet, JSTL, JavaBean, struts framework. Where JSP is the server page that displays the dynamic content, the servlet is the request that receives the client and responds, JSTL is the standard tag library that helps JSP display dynamic content, JavaBean is the model component of Java EE. It is important to note that the Struts framework technology is primarily extended to the servlet. In the middle tier, the servlet is an important component that controls other components.

The data-tier technology uses JDBC, JNDI, and hibernate frameworks. Among them, JDBC is the traditional way of database connection, Jndi and hibernate just extend the function, and not completely replace JDBC. Now popular is relational database, we use most of them, such as: SQL Server, Oracle, MySQL, etc., Hibernate framework technology is an object to operate relational database, to reduce the use of memory.

In addition, there is system integration technology. When you make a Web service, it's inevitable. In the present phase, if we develop with SSH framework technology, then spring is a system-Integrated framework technology and the most used system integration technology at this stage. System-Integrated JAX-WS technology is an important part of the Java EE platform, simplifying the work of using Java technology to develop Web services. However, I am a bit sorry, do not understand JAX-WS technology.

Said for so long, if there is a time, someone asked you what Java EE is, I hope you can see my opinion after the play, and finally, I wish the reader friends happy every day!!!