In this section of the operating principle of simple introduction  JSP  and strengths.For the first time in a JSP documents requested by the engine, JSP Servlet is transformed into a document JSP. This engine is itself a Servlet. The operating process of the JSP shown below:69137

(1) the JSP engine put the JSP files converting a Java source files (Servlet),  if you find the files have any grammar mistake JSP, conversion process will interrupt, and to the server and client output error messages.

(2) if converted, with the engine JSP javac Java source file compiler into a corresponding scale-up files.

(3) to create a the Servlet (JSP page), the transformation of the Servlet jspInit () method was executed, jspInit () method in the life cycle of Servlet executed only once.

(4) jspService () method invocation to the client requests. For each request, JSP engine to create a new thread for processing the request. If you have multiple clients and request the JSP files, JSP engine will create multiple threads. Each client requests a thread. To execute multi-thread can greatly reduce the requirement of system resources, improving the concurrency value and response time. But also should notice the multi-thread programming, due to the limited Servlet always in response to memory, so is very fast.

(5) if the file has been modified. The JSP, server will be set according to the document to decide whether to recompile, if need to recompile, will  replace the Servlet compile the memory and continue the process.论文网

(6) although the JSP efficiency is high, but at first when the need to convert and compile and some slight delay. In addition, if at any time due to reasons of system

resources, JSP engine will in some way of uncertain Servlet will remove from memory. When this happens jspDestroy () method was first call.

(7) and then Servlet examples were marked with "add" garbage collection. But in jspInit () some initialization work, if establish connection with database, or  to establish a network connection, from a configuration file take some parameters, such as, in jspDestory () release of the corresponding resources.

Based on a Java language has many other techniques JSP page dynamic characteristics, technical have embodied in the following aspects:

One simplicity and effectiveness

The JSP dynamic web pages with the compilation of the static HTML pages of writing is very similar. Just in the original HTML page add JSP tags, or some of the proprietary scripting (this is not necessary). So, a familiar with HTML page write design personnel may be easily performed JSP page development. And the developers can not only, and write script by JSP tags used exclusively others have written parts to realize dynamic pages. So, an unfamiliar with the web developers scripting language, can use the JSP make beautiful dynamic pages. And this in other dynamic web development is impossible.

Tow the independence of the program

The JSP are part of the family of the API Java, it has the general characteristics of the cross-platform Java program. In other words, is to have the procedure, namely the independence of the platform, 6 Write bided anywhere! .

Three procedures compatibility

The dynamic content can various JSP form, so it can show for all kinds of customers, namely from using HTML/DHTML browser to use various handheld wireless equipment WML (for example, mobile phones and pdas), personal digital equipment to use XML applications, all can use B2B JSP dynamic pages.

Four program reusability

In the JSP page can not directly, but embedded scripting dynamic interaction will be cited as a component part. So, once such a component to write, it can be repeated several procedures, the program of the reusability. Now, a lot of standard JavaBeans