What is servlet life cycle

The servlet life cycle refers to the entire process of Servlet from creation to destruction. The life cycle is divided into the following three stages: 1. Initialization stage. Before the Servlet container receives the first request for the Servlet, it will be initialized; 2. Service stage. After the Servlet object is initialized, when the request is received, the Servlet The container will process the request; 3. In the destruction phase, when the Servlet container is closed or the web application is uninstalled, the Servlet object will be destroyed.

The operating environment of this article: Windows10 system, Java19.0.1 version, Dell G3

Servlet life cycle refers to the Servlet from creation to destruction the whole process. The life cycle of a Servlet in a Web container is divided into the following stages: initialization, service, and destruction.

1. Initialization phase:

Before the Servlet container receives the first request for the Servlet, it will first call the Servlet's init() method for initialization. This method will only be called once and is used to perform some initialization operations, such as reading configuration files, establishing database connections, etc. During the initialization phase, the Servlet object is created and loaded into memory, but no requests have been received yet.

2. Service phase:

After the Servlet object is initialized, when a request is received, the Servlet container will call the service() method of the Servlet to process the request. This method will call the corresponding doGet(), doPost() and other methods according to the request type (GET, POST, etc.) to process the request and generate a response. The service() method generates a response object based on the processing result of the request and sends it to the client.

3. Destruction phase:

When the Servlet container is closed or the Web application is uninstalled, the Servlet's destroy() method will be called to destroy the Servlet object. The destroy() method will only be called once and is used to perform some cleanup operations, such as releasing resources, closing database connections, etc. During the destruction phase, the Servlet object is removed from memory and no longer receives any requests.

It should be noted that the life cycle of Servlet is managed by the Servlet container and cannot be directly controlled by developers. The Servlet container will create, initialize, call and destroy Servlet objects according to the actual situation. Throughout its lifecycle, Servlet objects can maintain state and share data even between different requests.

In addition, Servlet also provides some other life cycle methods that can be called at specific times, such as:

service() method: used to process requests and generate responses. This method is called every time a request is received.

doGet(), doPost() and other methods: handle requests according to the type of request. These methods will be called by the service() method.

destroy() method: used to perform cleanup operations. This method is called before the Servlet is destroyed.

Summary

The life cycle of Servlet includes three stages: initialization, service and destruction, which are completed through methods such as init(), service() and destroy(). operate. Understanding the life cycle of Servlet is very important for developing and debugging Servlet applications. Corresponding operations can be performed at different stages to improve the performance and stability of the application.

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