验证用户名密码：Servlet+Maven+Mysql+jdbc+Jsp

前言：

模拟我们日常使用网页使用账号密码进行登录网页，验证用户名和密码

用户数据表：

drop table if exists t_user;

create table t_user(
    id int(10) primary key auto_increment,
    username varchar(32) not null unique,
    password varchar(32) not null,
    realname varchar(128)
);
insert into t_user(username,password,realname) values('zhangzhixi','zhixi158','root');
insert into t_user(username,password,realname) values('zhangsan','123','普通用户');

select * from t_user;

Maven的依赖：

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <!--servlet依赖-->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
    </dependency>
    <!--jsp依赖-->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.0</version>
    </dependency>
    <!--mysql-jdbc依赖-->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.48</version>
    </dependency>
  </dependencies>

JSP页面：登录页面-成功页面-失败页面：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/login" method="post">
    账号
    <input type="text" name="username"><br>
    密码
    <input type="password" name="password"><br>
    <input type="submit" value="登录">
</form>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
欢迎您：

欢迎您:${pageContext.request.getAttribute("user")}用户

用户 </body> </html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
登录失败，请检查用户名密码是否正确
</body>
</html>

Servlet验证：

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
/**
 * @author zhangzhixi
 */
public class LoginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //解决乱码问题
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //获取用户在登录页面输入的值
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        PrintWriter out = response.getWriter();

        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            //1、注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2、获取连接
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/donglijiedian", "root", "zhixi158");
            //3、获取预编译的数据库操作对象
            String sql = "select * from t_user where username=? and password=?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, username);
            ps.setString(2, password);
            //4、执行sql
            rs = ps.executeQuery();
            //5、处理查询结果
            if (rs.next()) {
                //有数据代表有这个用户
                String realname = rs.getString("realname");
                request.setAttribute("user", realname);
                request.getRequestDispatcher("welcome.jsp").forward(request, response);
            } else {
                //没有这个用户
                System.out.println("没有这个用户");
                request.getRequestDispatcher("error.jsp").forward(request, response);
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //6、释放资源
            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (ps != null) {
                try {
                    ps.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    }
}

测试：

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原文地址：https://www.cnblogs.com/zhangzhixi/p/14135486.html