java实现用户登录

package mysql;

/*

• java程序实现用户登录，用户名和密码，数据库检查

• 演示被别人注入攻击

*/

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.Statement;

import java.util.Scanner;

public class JDBCDEMO2 {

public static void main(String[] args) throws Exception {

// TODO Auto-generated method stub

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

Connection con = DriverManager.getConnection

("jdbc.mysql://localhost:3306/mybase", "root" , "root");

Statement stat = con.createStatement();

Scanner sc = new Scanner(system.in );

String user = sc.nextLine();

String pass = sc.nextLine();

// 执行SQL语句，数据表，查询用户名和密码，如果存在，登录成功，不存在登录失败

String sql = "SELECT * FROM user WHERE username = '" +

user + "' AND PASSWORD = '" + pass + "'";

// + " = 'dsfsdfd' AND PASSWORD = 'wrethiyu'OR 1=1";

// String sql = "SELECT * FROM user WHERE username"

// + " = 'dsfsdfd' AND PASSWORD = 'wrethiyu'OR 1=1";

// String sql = "SELECT * FROM user WHERE username"

// + " = '" + user + "' AND PASSWORD = '" + pass + " 'OR 1=1";

ResultSet rs = stat.executeQuery(sql);

while(rs.next()) {

System.out .println

(rs.getString("username" + " " + rs.getString("password")));

}

rs.close();

stat.close();

con.close();

}

}

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

/**
 * @ClassName:      JDBCUtils
 * @Auther:         Mollen
 * @CreateTime:     2018-09-23  10:18:14
 * @Description:    JDBCUtils 数据库连接工具类
 */
public class JDBCUtils {

    /**
     * 1.定义成员变量datasource
     */
    private static DataSource ds;

    /**
     * 2.加载数据源
     */
    static {
        try {
            Properties pro = new Properties();
            pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("Druid.properties"));
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 3.获取连接池对象
     * @return
     */
    public static DataSource getDatasource(){
        return ds;
    }

    /**
     * 4.获取连接池Connection对象
     * @return
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }

    /**
     * 5.释放资源
     * @param st
     * @param conn
     */
    public static void close(PreparedStatement st, Connection conn) {
        close(null, st, conn);
    }

    /**
     * 5.释放资源重载方法
     * @param rs
     * @param st
     * @param conn
     */
    public static void close(ResultSet rs, PreparedStatement st, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

/**
 * @ClassName:      User
 * @Auther:         Mollen
 * @CreateTime:     2018-09-23  10:12:41
 * @Description:
 *                  User实体类
 */
 
public class User {

    private String userName;
    private String password;

    public User() {
    }

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

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

    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;
    }
}