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This article mainly introduces what the life cycle of JSP is like, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

JSP lifecycle

The key to understanding the underlying functions of JSP is to understand the lifecycle they follow.

The JSP life cycle is the whole process from creation to destruction, similar to the servlet life cycle, except that the JSP life cycle also includes compiling JSP files into servlet.

Here are several phases of the JSP lifecycle:

Compilation phase: the servlet container compiles servlet source files to generate servlet classes

Initialization phase: load the servlet class corresponding to JSP, create its instance, and call its initialization method

Execution phase: call the service method of the servlet instance corresponding to JSP

Destroy phase: call the destroy method of the servlet instance corresponding to JSP, and then destroy the servlet instance

. . .

JSP compilation

When the browser requests a JSP page, the JSP engine first checks to see if the file needs to be compiled. If the file has not been compiled, or has been changed since the last compilation, the JSP file is compiled.

The compilation process consists of three steps:

Parse the JSP file.

Convert the JSP file to servlet.

Compile servlet.

. . .

JSP initializes http://www.iis7.com/a/lm/yczmljgj/

After the container loads the JSP file, it calls the jspInit () method before providing any services to the request. If you need to perform a custom JSP initialization task, just override the jspInit () method, like this:

Public void jspInit () {

/ / initialization code

}

Generally speaking, the program is initialized only once, and so is servlet. Typically you can initialize a database connection, open a file, and create a query table in the jspInit () method.

. . .

JSP execution

This phase describes all request-related interactions in the JSP life cycle until it is destroyed.

When the JSP page is initialized, the JSP engine will call the _ jspService () method.

The _ jspService () method requires a HttpServletRequest object and a HttpServletResponse object as its parameters, like this:

Void _ jspService (HttpServletRequest request,HttpServletResponse response)

{

/ / Server processing code

}

The _ jspService () method is called once in each request and is responsible for generating the corresponding response, and it is also responsible for generating responses from all seven HTTP methods, such as GET, POST, DELETE, and so on.

. . .

JSP cleanup

The destroy phase of the JSP life cycle describes what happens when a JSP page is removed from the container.

The destruction method of the jspDestroy () method in JSP and servlet. Override the jspDestroy () method when you need to perform any cleanup, such as releasing a database connection or closing a folder, and so on.

The format of the jspDestroy () method is as follows:

Public void jspDestroy ()

{

/ / Clean the code

}

Thank you for reading this article carefully. I hope the article "what is the life cycle in JSP" shared by the editor will be helpful to you. At the same time, I also hope you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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