用JSP+Servlet做一个用户登录的例子

运用了mvc模式写的，代码如下：

LoginBiz.java

package com.biz

import com.entity.User

public interface LoginBiz {

boolean checkLogin(User user) throws Exception

}

LoginBizImpl.java

package com.biz

import com.dao.LoginDao

import com.dao.LoginDaoImpl

import com.entity.User

public class LoginBizImpl implements LoginBiz {

private LoginDao dao = new LoginDaoImpl()

public boolean checkLogin(User user) throws Exception {

return dao.checkLogin(user)

}

}

LoginDao.java

package com.dao

import com.entity.User

public interface LoginDao {

boolean checkLogin(User user) throws Exception

}

LoginDaoImpl.java

package com.dao

import java.sql.Connection

import java.sql.PreparedStatement

import java.sql.ResultSet

import com.entity.User

import com.util.SQLUtil

public class LoginDaoImpl implements LoginDao {

private SQLUtil sqlUtil = new SQLUtil()

private Connection conn = null

private PreparedStatement pstmt = null

private ResultSet rs = null

//验证用户信息

public boolean checkLogin(User user) throws Exception {

conn = sqlUtil.getConn()

String sql = "select * from user where username = ? and password = ?"

pstmt = conn.prepareStatement(sql)

pstmt.setString(1, user.getUsername())

pstmt.setString(2, user.getPassword())

rs = pstmt.executeQuery()

if(rs.next()){

return true

}

return false

}

}

User.java

package com.entity

public class User {

private int id

private String username

private String password

public int getId() {

return id

}

public void setId(int id) {

this.id = id

}

public String getUsername() {

return username

}

public void setUsername(String username) {

this.username = username

}

public String getPassword() {

return password

}

public void setPassword(String password) {

this.password = password

}

}

LoginServlet.java

package com.servlet

import java.io.IOException

import java.io.PrintWriter

import javax.servlet.ServletException

import javax.servlet.http.HttpServlet

import javax.servlet.http.HttpServletRequest

import javax.servlet.http.HttpServletResponse

import com.biz.LoginBiz

import com.biz.LoginBizImpl

import com.entity.User

public class LoginServlet extends HttpServlet {

private LoginBiz biz = new LoginBizImpl()

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doPost(request,response)

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

String username = request.getParameter("username")

String password = request.getParameter("password")

User user = new User()

user.setUsername(username)

user.setPassword(password)

boolean b = true

try {

b = biz.checkLogin(user)

} catch (Exception e) {

e.printStackTrace()

}

if(b == true){

request.getRequestDispatcher("/success.jsp").forward(request, response)

}else{

request.getRequestDispatcher("/error.jsp").forward(request, response)

}

}

}

ShowDate.java

package com.servlet

import java.io.IOException

import java.io.PrintWriter

import javax.servlet.ServletException

import javax.servlet.http.HttpServlet

import javax.servlet.http.HttpServletRequest

import javax.servlet.http.HttpServletResponse

public class ShowDate 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 year = request.getParameter("year")

request.setCharacterEncoding("utf-8")

request.setAttribute("year", year)

request.getRequestDispatcher("/showDate.jsp").forward(request, response)

}

}

SQLUtil.java

package com.util

import java.sql.Connection

import java.sql.DriverManager

import java.sql.PreparedStatement

import java.sql.ResultSet

import java.sql.SQLException

public class SQLUtil {

private static Connection conn

private static PreparedStatement pstmt

private static ResultSet rs

//创建连接

public static Connection getConn(){

String url = "jdbc:mysql://localhost:3306/test"

String user = "root"

String password = "123456"

try {

Class.forName("com.mysql.jdbc.Driver")

conn = DriverManager.getConnection(url, user, password)

} catch (SQLException e) {

e.printStackTrace()

return null

} catch (ClassNotFoundException e) {

e.printStackTrace()

return null

}

return conn

}

//关闭连接

public static void closeConn(Connection conn,PreparedStatement pstmt,ResultSet rs){

if(rs != null){

try {

rs.close()

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

}

if(pstmt != null){

try {

pstmt.close()

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

}

if(conn != null){

try {

conn.close()

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

}

}

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

<servlet>

<description>This is the description of my J2EE component</description>

<display-name>This is the display name of my J2EE component</display-name>

<servlet-name>LoginServlet</servlet-name>

<servlet-class>com.servlet.LoginServlet</servlet-class>

</servlet>

<servlet>

<description>This is the description of my J2EE component</description>

<display-name>This is the display name of my J2EE component</display-name>

<servlet-name>ShowDate</servlet-name>

<servlet-class>com.servlet.ShowDate</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>LoginServlet</servlet-name>

<url-pattern>/loginServlet</url-pattern>

</servlet-mapping>

<servlet-mapping>

<servlet-name>ShowDate</servlet-name>

<url-pattern>/showDate</url-pattern>

</servlet-mapping>

<welcome-file-list>

<welcome-file>index.jsp</welcome-file>

</welcome-file-list>

</web-app>

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

</head>

<body>

<form action="loginServlet" method="post">

<table>

<tr>

<td>用户名：</td>

<td><input type="text" name="username" /></td>

</tr>

<tr>

<td>密 码：</td>

<td><input type="password" name="password" /></td>

</tr>

<tr>

<td colspan="2"><input type="submit" value="登录"/></td>

</tr>

</table>

</form>

</body>

</html>

success.jsp

<%@ page language="java" contentType="text/htmlcharset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/htmlcharset=UTF-8">

<title>Insert title here</title>

</head>

<body>

<form action="showDate" method="post">

<table>

<tr>

<td>年</td>

<td>

<select name="year">

<option>2002</option>

<option>2003</option>

<option>2004</option>

<option>2005</option>

<option>2006</option>

</select>

</td>

</tr>

<tr>

<td clospan="2"><input type="submit" value="提交"/></td>

</tr>

</table>

</form>

</body>

</html>

error.jsp

<%@ page language="java" contentType="text/htmlcharset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/htmlcharset=UTF-8">

<title>Insert title here</title>

</head>

<body>

您输入的用户名或密码错误，请重新输入！<a href='javascript:history.go(-1)'>返回上一页</a>

</body>

</html>

showDate.jsp

<%@ page language="java" contentType="text/htmlcharset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/htmlcharset=UTF-8">

<title>Insert title here</title>

</head>

<body>

您选择的年份是${year }

</body>

</html>

例如：在用户提交用户名和密码之后，进入樱棚到loginServlet后，通过获取页面上checkbox的脊斗则值来判断用户是否需要记住密码，如果需要的话，使用：Cookie cookie = new Cookie("testkey","testvalue")cookie.setMaxAge(3600)// 有效时间，单位是秒cookie.setPath("abc")response.addCookie(cookie)如上几句来保存cookie。在登录页面的时候，需要使用：Cookie[] cookies = request.getCookies()for (int i = 0cookies != null &&i <cookies.lengthi++) { System.out.println(cookies[i].getName() + "=" + cookies[i].getValue())}来获取cookie的值判断用户曾经是否已经记住密码，如果是的话销蠢，则直接调用cookie的值来进行登录，如果不是，则正常登录

你这只是贴出来前端页面，servlet有个web.xml文件配置正确吗？名称和form表单请求名一致吗？看看配置文件有没有配置后缀，伍族比如action或do，如果有，需要加在servlet请求名后面，在登录前点击F12，检查请求是否状态为族橘大200，或者后台跳转页面是兆竖否正常调整，后端加个断点跟踪一下

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