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This article will explain in detail the three stages of the servlet life cycle. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

Servlet lifecycle: 1. In the initialization phase, the Servlet container creates an Servlet instance and calls the [init ()] method; 2, in the client request processing phase, the server generates a new thread to process each client request; and 3, in the termination phase, call the destroy method to terminate.

Servlet Lifecycle:

1. The life cycle of servlet

There are three main ways:

Init () initialization phase

Service () processing client request phase

Destroy () termination phase

Initialization phase:

The Servlet container loads Servlet. After loading, the Servlet container creates a Servlet instance and calls the init () method. The init () method is called only once.

The Servlet container loads Servlet in the following situations:

Some servlet is automatically loaded when the Servlet container starts, which requires adding 1 in the web.xml file to achieve this

After the Servlet container is started, the customer sends a request to Servlet for the first time

After the Servlet class file is updated, reload

Processing client request phase:

Every time a client request is received, the server generates a new thread to process.

For a user's Servlet request, the Servlet container creates a request-specific ServletRequest and ServletResponse.

For tomcat, it puts the passed parameters into a HashTable, which is a key-value mapping of String- > String []

Termination phase:

When the web application is terminated, or the Servlet container terminates, or when Servlet reloads a new instance of Servlet, the Servlet container calls the destroy () method of Servlet.

2. The working principle of servlet

The client sends a request, and Servlet calls the service () method to respond to the request, and the service () method matches the requested method, enters the corresponding logic layer, and completes the response to the request.

However, there are no doGet (), doPost () and other methods in the Servlet interface and GenericServlet interface. These methods are defined in HttpServlet, but the Error information is returned, so these methods are overridden every time you define Servlet.

Sertvlet and GenericServlet are not specific to any protocol, while HttpServlet is specific to the Http protocol, so the service () method in HttpServlet strongly converts ServletRequest,ServletResponse to HttpRequest and HttpResponse, and finally calls its own service method to complete the response.

This is the end of the three stages of the servlet life cycle. I hope the above content can be of some help and learn more knowledge. If you think the article is good, you can share it for more people to see.

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