转载：http://blog.sina.com.cn/s/blog_5c5bc9070100zhsn.html
1) redirect 方式
response.sendRedirect("/a.jsp");
页面的路径是相对路径。sendRedirect可以将页面跳转到任何页面，不一定局限于本web应用中，如：
response.sendRedirect("URL");
跳转后浏览器地址栏变化。
这种方式要传值出去的话，只能在url中带parameter或者放在session中，无法使用request.setAttribute来传递。
2) forward方式
RequestDispatcher dispatcher = request.getRequestDispatcher("/a.jsp");
dispatcher .forward(request, response);
Servlet页面跳转的路径是相对路径。forward方式只能跳转到本web应用中的页面上。
跳转后浏览器地址栏不会变化。
使用这种方式跳转，传值可以使用三种方法：url中带parameter，session，request.setAttribute
实例：
第一种方法:
AccountBean.java文件
package com.ht.servlet;
public class AccountBean {
private String username = "";
private String password = "";
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
}
CheckAccount.java文件
package com.ht.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class CheckAccount extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req,resp);
}
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
HttpSession session = req.getSession();
AccountBean account = new AccountBean();
String username = req.getParameter("username");
String pwd = req.getParameter("pwd");
account.setPassword(pwd);
account.setUsername(username);
if((username != null)&&(username.trim().equals("jsp"))) {
if((pwd != null)&&(pwd.trim().equals("1"))) {
System.out.println("success");
session.setAttribute("account", account);
String login_suc = "success.jsp";
resp.sendRedirect(login_suc);
return;
}
}
String login_fail = "fail.jsp";
resp.sendRedirect(login_fail);
return;
}
}
第二种方法：
package servlets;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String user = request.getParameter("user");
RequestDispatcher rd = null;
if(user!=null&&user.equals("admin"))
{
request.getSession().setAttribute("login", "true");
rd = request.getRequestDispatcher("admin.html");
rd.forward(request, response);
}
else if(user!=null&&user.equals("common"))
{
request.getSession().setAttribute("login", "true");
rd = request.getRequestDispatcher("common.html");
rd.forward(request, response);
}
else
response.sendRedirect("login.html");
}
}
