HttpServletRequest 类

1.HttpServletRequest 类的常用方法:
i. getRequestURI() 获取请求的资源路径
ii. getRequestURL() 获取请求的统一资源定位符（绝对路径）
iii. getRemoteHost() 获取客户端的 ip 地址
iv. getHeader() 获取请求头
v. getParameter() 获取请求的参数
vi. getParameterValues() 获取请求的参数（多个值的时候使用），返回数组
vii. getMethod() 获取请求的方式 GET 或 POST
viii. setAttribute(key, value); 设置域数据
ix. getAttribute(key); 获取域数据
x. getRequestDispatcher() 获取请求转发对象

代码：

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/requestServlet1")
public class RequestServlet1 extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //结果：/Day_06/requestServlet1
        System.out.println("获取请求的资源路径: "+request.getRequestURI());
        //结果： http://localhost:8080/Day_06/requestServlet1
        System.out.println("获取请求的统一资源定位符（绝对路径）: "+request.getRequestURL());
        //结果：GET
        System.out.println("获取请求的方式 GET 或 POST: "+request.getMethod());
        //结果：Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36
        System.out.println("获取请求头: "+request.getHeader("User-Agent"));
        //结果：127.0.0.1
        System.out.println("获取客户端的 ip 地址: "+request.getRemoteHost());
    }
}

2.doGet 请求的中文乱码：

代码：

// 获取请求参数
String username = req.getParameter("username");
//1 先以 iso8859-1 进行编码
//2 再以 utf-8 进行解码
username = new String(username.getBytes("iso-8859-1"), "UTF-8");

3.POST 请求的中文乱码：

代码：

req.setCharacterEncoding("UTF-8");

 4.请求转发：

  1）. 转发地址栏路径不变
  2）. 转发只能访问当前服务器下的资源
  3）. 转发是一次请求，可以使用request对象来共享数据

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/requestServlet2")
public class RequestServlet2 extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setAttribute("key", "人才");
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/requestServlet3");
        requestDispatcher.forward(request, response);
    }
}

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.jar.JarOutputStream;

@WebServlet("/requestServlet3")
public class RequestServlet3 extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("value: "+request.getAttribute("key"));
    }
}