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This article focuses on "what are the HTTP Servlet API", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn what are the HTTP Servlet APIs.

HTTP Servlet API provided by javax.servlet.http.

The HTTP Servlet API uses an HTML table to send and receive data. To create a HTTP Servlet, extend the Http Servlet class, which is a subclass of GenericServlet that uses specialized methods to handle HTML tables. The HTML form is defined by the and tags. The form typically contains input fields, such as text input fields, check boxes, radio buttons, and select lists, and buttons for submitting data. When submitting information, they also specify which Servlet (or other program) the server should execute. The HttpServlet class contains methods like init (), destroy (), service (), and so on. Where the init () and destroy () methods are inherited.

(1) init () method

The init () method is executed only once during the lifetime of the Servlet. It is executed when the server loads the Servlet. The server can be configured to load the Servlet when starting the server or client * * to access Servlet. No matter how many clients access Servlet, init () is not repeated.

The default init () method usually meets the requirements, but it can also be overridden with a custom init () method, typically managing server-side resources. For example, you might write a custom init () to load GIF images only once, improving the performance of Servlet returning GIF images and containing multiple client requests. Another example is initializing a database connection. The default init () method sets the initialization parameters of Servlet and starts the configuration with its ServletConfig object parameters, so all Servlet that override the init () method should call super.init () to ensure that these tasks are still performed. Before calling the service () method, you should make sure that the init () method is completed.

(2) service () method

The ervice () method is the core of Servlet. Whenever a customer requests a HttpServlet object, the object's service () method is called and passed to the method a ServletRequest object and a ServletResponse object as parameters. The service () method already exists in HttpServlet. The default service function is to invoke the do function corresponding to the method requested by HTTP. For example, if the HTTP request method is GET, doGet () is called by default. Servlet should override the do functionality for the HTTP methods supported by Servlet. Because the HttpServlet.service () method checks to see if the request method calls the appropriate handling method, it is not necessary to override the service () method. Just override the corresponding do method.

When a customer makes an HTTP POST request through the HTML form, the doPost () method is called. The parameters related to the POST request are sent from the browser to the server as a separate HTTP request. When you need to modify server-side data, you should use the doPost () method.

The doGet () method is called when a customer makes an HTTP GET request through an HTML form or requests a URL directly.

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