6----重定向和转发的区别和使用_转发和重定向 302-优快云博客

本文链接：https://blog.youkuaiyun.com/u014185088/article/details/98791494

本文详细解析了页面跳转中的重定向302与转发（getRequestDispatcher）两种方式的区别与应用场景，包括它们的行为特性、请求次数、浏览器地址变化、request数据处理及路径问题，通过具体Java代码示例进行说明。

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目的：页面跳转

重定向302（response.sendRedirect("");）：定位到新的网站资源位置

特点：

1 客户端行为

2 两次请求

3 浏览器地址改变

4 request数据丢失

5 “/项目名/资源”代表web站点的根路径

Html:

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title>简单注册案例</title>
	</head>
	<body>
	
		<form action="/registerDemo/registerServlet" method="post">
			用户名：<input type="text" name="username" value="" /><br />
			密码：<input type="password" name="password" /><br />
			Eamil:<input type="text" name="email" /><br/>
			<input type="submit" value="注册"/>
		</form>
		
	</body>
</html>

JAVA

package com.register.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

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

@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public RegisterServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//1 设置编码  后期采用map实现
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=utf-8");
		//2 读取数据
		String username=request.getParameter("username");
		String password=request.getParameter("password");
		String email=request.getParameter("email");
		
		// 3 验证数据
		PrintWriter out=response.getWriter();
		if (username==null||username.trim().equals("")) {
			out.write("用户名不能为空！");
			return;
		}
		
		if (password==null||password.trim().equals("")) {
			out.write("密码不能为空！");
			return;
		}
		
		if (email==null||email.trim().equals("")) {
			out.write("email不能为空！");
			return;
		}
		
		//4 保存数据库
		Connection connection=null;
		PreparedStatement pStat=null;
			//注册驱动
			try {
				Class.forName("com.mysql.jdbc.Driver");
				//获取连接
				String url="jdbc:mysql://localhost:3306/javastudy?useSSL=false";
				String user="root";
				String pass="";
				connection=DriverManager.getConnection(url, user, pass);
				//创建命令
				pStat=connection.prepareStatement("INSERT INTO db_user (username,PASSWORD,email) VALUE(?,?,?)");
				pStat.setString(1, username);
				pStat.setString(2, password);
				pStat.setString(3, email);
				
				int result=pStat.executeUpdate();
				if (result>0) {
					response.sendRedirect("/registerDemo/index.html");
					out.write("注册成功");
				}else {
					out.write("注册失败");
				}
				
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} finally {
				if (connection!=null) {
					try {
						connection.close();
					} catch (SQLException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
					
				}
				
				if (pStat!=null) {
					try {
						pStat.close();
					} catch (SQLException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
					
				}
			}
			
	
		
		
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

转发（getRequestDispatcher）：只能转发到同一个web下的url，客户端感觉不到转发

特点：

1 服务端行为

2 1次请求

3 浏览器地址不变

4 request数据不丢失

5 转发同一个web应用

java:

package com.register.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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;

/**
 * Servlet implementation class DispatcherServlet
 */
@WebServlet("/dispatcherServlet")
public class DispatcherServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DispatcherServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//1 设置编码  后期采用map实现
				request.setCharacterEncoding("UTF-8");
				response.setContentType("text/html;charset=utf-8");
				//2 读取数据
				String username=request.getParameter("username");
				String password=request.getParameter("password");
				String email=request.getParameter("email");
				
				// 3 验证数据
				PrintWriter out=response.getWriter();
				if (username!=null||username.trim().equals("111")) {
					//转发
					//获取转发器
					RequestDispatcher dispatcher = request.getRequestDispatcher("/registerServlet");
					//转发
					dispatcher.forward(request, response);
					return;
				}
		
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

Html:

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title>转发案例</title>
	</head>
	<body>
	
		<form action="/registerDemo/dispatcherServlet" method="post">
			用户名：<input type="text" name="username" value="" /><br />
			密码：<input type="password" name="password" /><br />
			Eamil:<input type="text" name="email" /><br/>
			<input type="submit" value="注册"/>
		</form>
		
	</body>
</html>