A brief introduction to the Servlet life cycle and working principle (pictures and text)

This article brings you a brief introduction (pictures and texts) about the Servlet life cycle and working principle. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Servlet life cycle

Process: Loading--> Instantiation--> Service--> Destruction

init(): In the Servlet life cycle, the init() method is only executed once, no matter how many clients access it. Will be executed repeatedly. It is executed when the server loads the Servlet, and the load initializes the Servlet object.

service(): When the Servlet container receives a request, the Servlet container will create a ServletRequest for the request. ServletResponse object. Then call the service() method. And pass these two parameters to the service() method. The service() method obtains the requested information through the ServletRequest object. and process the request. Then generate the response result of this request through the ServletResponse object.

destroy(): In the Servlet life cycle, the destroy() method will only be executed once. When the Servlet object ends its life cycle, it is responsible for releasing resources.

Servlet working principle

##After the web server receives an http request, the web server will hand over the request to the servlet container The servlet container first parses the requested URL and finds the corresponding processing servlet according to the web.xml configuration file At the same time, pass the request and response objects to it. The servlet can know the client's requester, request information and other information through the request object. After processing the request, the servlet will put all the information that needs to be returned into the response object and return it to the client Once the servlet has processed the request, the servlet container refreshes the response object and returns control to the web server.

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