- _nosay
Servlet跳转之重定向
2017-11-20 11:27:18
重定向简介:
重定向是根据服务器返回的状态码来实现的.客户端浏览器在请求服务器的时候,服务端会返回一个状态码.服务器通过HttpServletResponse的setStatus(int status)方法来设置状态码.如果服务器这个时候返回的状态码是３０１或者３０２,则浏览器会到新的网址重新请求该资源,服务器的响应中会带着这个新资源的地址.
请求重定向的相关代码:
//设置状态码为３０２,SC_MOVED_TEMPORAILY就是３０２的静态常量response.setStatus(HttpServletResponse.SC_MOVED_TEMPOPAILY);
//在请求头在携带新的资源地址
response.setHeader("Location","http://www.baidu.com");
为了使用方便HttpServletResponse中将setStatus和setHeader这两人种方法合并到一起叫做sendRedirect(String location);
接下来实现登陆成功以后,跳转到用户中心界面
首行建立一个用户中心简单界面,member.jsp具体内容如下:
<%-- Created by IntelliJ IDEA. User: nosay Date: 17-11-20 Time: 上午11:19 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <h1>这里是用户中心</h1> </body> </html>
在Test5Servlet文件中,加入登陆成功的相应代码,具体代码如下:
package com.nosay.servlet;
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(name = "Test5Servlet",urlPatterns = "/test5")
public class Test5Servlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = "nosay";
String pass = "123456";
String name = request.getParameter("username");
String password = request.getParameter("password");
if(!name.equals(username))
{
request.setAttribute("errorMessage","帐户不存在");
request.getRequestDispatcher("/loginError.jsp").forward(request,response);
//帐户不存在
}else if(!password.equals(pass))
{
request.setAttribute("errorMessage","密码错误");
request.getRequestDispatcher("/loginError.jsp").forward(request,response);
//密码错误
}else{ //登陆成功
response.setStatus(HttpServletResponse.SC_MOVED_TEMPORARILY);
response.setHeader("Location","/member.jsp");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}这样我们输入正确的用户名,以及密码.成功的跳转到了正确的页面,即用户中心界面(member.jsp)
其实,为了方便我们实现重定向功能,有一个简化的sendRedirect(String location);相关代码如下所示:
package com.nosay.servlet;
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(name = "Test5Servlet",urlPatterns = "/test5")
public class Test5Servlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = "nosay";
String pass = "123456";
String name = request.getParameter("username");
String password = request.getParameter("password");
if(!name.equals(username))
{
request.setAttribute("errorMessage","帐户不存在");
request.getRequestDispatcher("/loginError.jsp").forward(request,response);
//帐户不存在
}else if(!password.equals(pass))
{
request.setAttribute("errorMessage","密码错误");
request.getRequestDispatcher("/loginError.jsp").forward(request,response);
//密码错误
}else{ //登陆成功
// response.setStatus(HttpServletResponse.SC_MOVED_TEMPORARILY);
// response.setHeader("Location","/member.jsp");
response.sendRedirect("/member.jsp");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}这样同样能实现相同的效果.
请求转发和重定向有什么功别呢?
１.重定向的地址栏会发生变化 ,转发不会.
２.重定向是两次请求两次响应,转发是一次请求一次响应.
３.重定向路径需要加工程名,转发路径不需要加工程名.
４.重定向可以跳转到任何网站,转发只能在服务器内部进行.