版权声明

本文原创作者：谷哥的小弟
作者博客地址：http://blog.csdn.net/lfdfhl

在这里插入图片描述
在本节教程中，我们完成项目的登录功能。

User

请在bean包中创建User类，代码如下：

package com.cn.bean;
/**
 * 本文作者：谷哥的小弟
 * 博客地址：http://blog.csdn.net/lfdfhl
 */
public class User {
    private int id;
    private String username;
    private String password;

    public User() {
    }

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = 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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

图示如下：

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登录页面

请在web文件夹下创建登录页面index.jsp，代码如下：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <meta charset="UTF-8">
    <title>首页</title>
    <style type="text/css">
        body {
            background: #e2e6c2;
        }

        #AllLogin {
            margin-top: 15%;
            text-align: center;
        }

        .loginDiv {
            background: #fff;
            padding: 20px 30px;
            width: 400px;
            margin: 0 auto;
            text-align: center;
        }

        button {
            width: 180px;
            height: 40px;
            background: #17334e;
            border: 1px solid #fff;
            color: #fff;
            font-size: 14px;
        }

        input {
            width: 260px;
            padding: 4px 2px;
        }

        .tips {
            width: 440px;
            height: 30px;
            margin: 5px auto;
            background: #fff;
            color: #17334e;
            border: 1px solid #ccc;
            display: none;
            line-height: 30px;
            padding-left: 20px;
            font-size: 13px;
        }
    </style>

    <script src="js/jquery-1.8.3.js"></script>
    <script type="text/javascript">
        $(function () {
            $("#username,#password").blur(function () {
                var value = $(this).val();
                if (value.trim() == '') {
                    $(".tips").css("display", "block")
                    $(".tips").html("输入内容不能为空!");
                } else {
                    $(".tips").css("display", "none")
                }
            });
        });
    </script>
</head>
<body>
<div id="AllLogin">
    <div id="tipsDivID" class="tips"></div>
    <div class="loginDiv">
        <form action="${pageContext.request.contextPath}/LoginServlet" method="post">
            <p>
                <label>用户名：<input id="username" type="text" name="username"></label>
            </p>
            <p>
                <label>密　码：<input id="password" type="password" name="password"></label>
            </p>
            <p>
                <button type="submit" id="login">登录</button>
            </p>
        </form>
    </div>
</div>
</body>
</html>

图示如下：

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LoginServlet

请在servlet包下创建LoginServlet处理用户登录。

登录成功：将当前用户保存至Session中再跳转到ShowStudentServlet查询所有学生并显示
登录失败：跳转到登录页面重新登录

代码如下：

package com.cn.servlet;

import com.cn.util.C3P0Utils;
import com.cn.bean.User;
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 javax.servlet.http.HttpSession;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

@WebServlet(name = "LoginServlet", urlPatterns = "/LoginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            connection = C3P0Utils.getConnection();
            String sql = "SELECT * FROM user where username=? and password=?";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, username);
            preparedStatement.setString(2, password);
            resultSet = preparedStatement.executeQuery();
            boolean isSuc = resultSet.next();
            if (isSuc) {
                System.out.println("success");
                User user = new User(username,password);
                HttpSession session = request.getSession();
                session.setAttribute("user",user);
                String contextPath = request.getContextPath();
                response.sendRedirect( contextPath+"/ShowStudentServlet");
            } else {
                System.out.println("error");
                String contextPath = request.getContextPath();
                response.sendRedirect(contextPath + "/index.jsp");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            C3P0Utils.release(connection, preparedStatement, resultSet);
        }
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}