Java HttpServletRequest Guide

In Java, you can retrieve information about an HTTP request using the HttpServletRequest object.

Firstly, make sure to import the HttpServletRequest class in your code.

import javax.servlet.http.HttpServletRequest;

Then, in the `doGet()` or `doPost()` method of the Servlet, you can use the `HttpServletRequest` object to obtain information about the request, such as the request method, request URL, request parameters, and so on. Here are some examples of commonly used methods:

protected void doGet(HttpServletRequest request, HttpServletResponse response) {
    // 获取请求方法
    String method = request.getMethod();
    System.out.println("请求方法：" + method);
    
    // 获取请求URL
    String url = request.getRequestURL().toString();
    System.out.println("请求URL：" + url);
    
    // 获取请求参数
    String paramValue = request.getParameter("paramName");
    System.out.println("请求参数值：" + paramValue);
    
    // 获取请求头信息
    String userAgent = request.getHeader("User-Agent");
    System.out.println("User-Agent：" + userAgent);
    
    // 获取请求的IP地址
    String ipAddress = request.getRemoteAddr();
    System.out.println("请求IP地址：" + ipAddress);
    
    // 获取Session对象
    HttpSession session = request.getSession();
}

These methods are just a part of the HttpServletRequest class, you can use other methods as needed to obtain more request information.

Before using the HttpServletRequest object, make sure you have created a Servlet class and overridden the doGet() or doPost() method.