MD5加密

 项目结构如下：

MD5加密代码如下： 

package com.jd.tool; import java.math.BigInteger; import java.security.MessageDigest; public class MD5Tool { public static String encrypt(String password) { byte[] bytes = null; try { MessageDigest messageDigest = MessageDigest.getInstance("MD5"); messageDigest.update(password.getBytes());//加密 bytes = messageDigest.digest();//获得加密结果 } catch (Exception e) { e.printStackTrace(); } String result = new BigInteger(1, bytes).toString(16);// 将加密后的数据转换为16进制数字 // 生成数字未满32位，则前面补0 for (int i = 0; i < 32 - result.length(); i++) { result = "0" + result; } return result; } }

 

在实际登录操作中：

package com.jd.test; import java.util.Scanner; import java.util.UUID; import com.jd.tool.MD5Tool; import com.jd.tool.db.DBLink; public class Main { public static void main(String[] args) { System.out.println("*********************************"); System.out.println("*\t\t\t\t*"); System.out.println("*\t欢迎使用注册登录系统\t\t*"); System.out.println("*\t\t\t\t*"); System.out.println("*********************************"); while (true) { menu(); } } static void menu() { DBLink db = new DBLink(); System.out.println("1、注册");//用户名 密码 确认密码 System.out.println("2、登录");//用户名和密码 System.out.println("3、退出");//System.exit(0); System.out.println("请输入操作，以Enter键结束:"); Scanner scanner = new Scanner(System.in); int option = scanner.nextInt(); switch (option) { case 1:{ System.out.println("请输入用户名"); String user_name = scanner.next(); String sql = "select id from user_info where user_name = ?"; if(db.exist(sql,user_name)) { System.out.println("用户名已存在，操作中止！"); return; } System.out.println("请输入用密码"); String password = scanner.next(); System.out.println("请再次输入密码"); String repassword = scanner.next(); if(!password.equals(repassword)) { System.out.println("两次输入密码不一致,操作中止"); return; } String id = UUID.randomUUID().toString(); password = MD5Tool.encrypt(password);//在注册时为防止管理员可以直接在后台看到密码，采用MD5加密，将所有的输入密码转换为32位的代码。 sql = "insert into user_info (id,user_name,password) value ('"+id+"',?,?)"; if(db.update(sql,user_name,password)) { System.out.println("注册成功"); return; } System.out.println("注册失败"); break; } case 2: System.out.println("请输入用户名"); String user_name = scanner.next(); System.out.println("请输入用密码"); String password = scanner.next(); password = MD5Tool.encrypt(password);//在进行登陆操作时，由于数据库中存入的是加密后的32位代码，因此需要在将输入的密码转化为32位代码与数据库中的信息进行比对。成功即可登录。 String sql = "select id from user_info where user_name = ？ and password = ？"; if(db.exist(sql,user_name,password)) { System.out.println("登录成功"); break; } System.out.println("登录失败"); break; case 3: System.out.println("退出登录"); System.exit(0); break; default: System.out.println("I'm Sorry,there is not the "+option+" option,please try again."); } } }

加密解析如上。 

DBLink代码：

package com.jd.tool.db; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import org.apache.log4j.Logger; import com.jd.tool.PropertiesTool; /** * 数据库管理工具类 * * @author GaoHuanjie */ public class DBLink { private Logger logger = Logger.getLogger(DBLink.class); /** * 获取数据库连接 * * @author GaoHuanjie */ private Connection getConnection() { try { Class.forName("com.mysql.jdbc.Driver");//加载驱动 String userName = PropertiesTool.getValue("db.username"); String password = PropertiesTool.getValue("db.password"); String url = PropertiesTool.getValue("db.url"); return DriverManager.getConnection(url, userName, password);//获取连接 } catch (Exception e) { logger.debug(e.getMessage(), e); } return null; } /** * 判断SQL语句是否能查出数据 * * @author GaoHuanjie */ public boolean exist(String sql) { Connection connection = null; Statement statement =null; ResultSet resultSet=null; try { connection = getConnection();//获取连接 statement = connection.createStatement(); resultSet= statement.executeQuery(sql);//执行sql,将查询的数据存到ResultSet类型的变量中 return resultSet.next(); } catch (Exception e) { logger.debug(e.getMessage(), e); }finally { close(resultSet,statement,connection); } return false; } /** * 判断SQL语句是否能查出数据 * * @author GaoHuanjie */ public boolean exist(String sql, Object ...params) { Connection connection = null; PreparedStatement preparedStatement =null; ResultSet resultSet=null; try { connection = getConnection();//获取连接 preparedStatement = connection.prepareStatement(sql); for (int i = 0; i < params.length; i++) { preparedStatement.setObject(i+1, params[i]); } resultSet= preparedStatement.executeQuery();//执行sql,将查询的数据存到ResultSet类型的变量中 return resultSet.next(); } catch (Exception e) { logger.debug(e.getMessage(), e); }finally { close(resultSet,preparedStatement,connection); } return false; } /** * 查询数据 * * @author GaoHuanjie */ public void select(String sql,IRowMapper rowMapper) {//接口无法创建对象，所以rowMapper参数一定指向IRowMapper接口实现类对象 Connection connection = null; Statement statement =null; ResultSet resultSet=null; try { connection = getConnection();//获取连接 statement = connection.createStatement(); resultSet= statement.executeQuery(sql);//执行sql,将查询的数据存到ResultSet类型的变量中 rowMapper.rowMapper(resultSet);//因为rowMapper参数指向IRowMapper接口实现类对象，所以此处将调用接口实现类中所实现的rowMapper方法 多态 } catch (Exception e) { logger.debug(e.getMessage(), e); }finally {//释放资源 close(resultSet,statement,connection); } } /** * 查询数据 * * @author GaoHuanjie */ public void select(String sql,IRowMapper rowMapper,Object ...params) { Connection connection = null; PreparedStatement preparedStatement =null; ResultSet resultSet=null; try { connection = getConnection();//获取连接 preparedStatement= connection.prepareStatement(sql);//含有？号占位符的sql for (int i = 0; i < params.length; i++) { preparedStatement.setObject(i+1, params[i]);//为？号赋值 } resultSet= preparedStatement.executeQuery();//执行sql rowMapper.rowMapper(resultSet);//因为rowMapper参数指向IRowMapper接口实现类对象，所以此处将调用接口实现类中所实现的rowMapper方法 多态 } catch (Exception e) { logger.debug(e.getMessage(), e); }finally {//释放资源 close(resultSet,preparedStatement,connection); } } /** * 修改（insert、update和delete）数据 * * @author GaoHuanjie */ public boolean update(String sql) { Connection connection = null; Statement statement = null; try { connection = getConnection();//获取数据库连接对象，一个对象表示一次数据库连接 statement = connection.createStatement();//获取Statement对象 int result = statement.executeUpdate(sql);//执行sql语句，返回受影响的行数，仅限于数据insert、update和delete return result>0;//处理结果 } catch (Exception e) { logger.debug(e.getMessage(), e); }finally {//即便有异常也会执行代码 close(statement,connection); } return false; } /** * 修改（insert、update和delete）数据 * * @author GaoHuanjie */ public boolean update(String sql,Object ...params) { Connection connection= null; PreparedStatement preparedStatement= null; try { connection= getConnection(); preparedStatement= connection.prepareStatement(sql);//含有？号占位符的sql for (int i = 0; i < params.length; i++) { preparedStatement.setObject(i+1, params[i]);//为？号赋值 } return preparedStatement.executeUpdate()>0; } catch (Exception e) { logger.debug(e.getMessage(), e); }finally { close(preparedStatement,connection); } return false; } /** * 释放资源 * * @author GaoHuanjie */ private void close(Statement statement,Connection connection) { try { if(statement!=null) {//有可能由于异常导致statement没有赋值，比如url出错 statement.close(); } } catch (SQLException e) { logger.debug(e.getMessage(), e); } try { if(connection!=null) { connection.close(); } } catch (SQLException e) { logger.debug(e.getMessage(), e); } } /** * 释放资源 * * @author GaoHuanjie */ private void close(ResultSet resultSet,Statement statement,Connection connection) {//重载 try { if(resultSet!=null) { resultSet.close(); } } catch (SQLException e) { logger.debug(e.getMessage(), e); } close(statement,connection); } }

Properties代码：

package com.jd.tool; import java.io.IOException; import java.io.InputStream; import java.util.Properties; public class PropertiesTool { private static Properties properties = new Properties(); static { InputStream inputStream = PropertiesTool.class.getClassLoader().getResourceAsStream("db.properties");//将db.properties变为javaIO流对象 try { properties.load(inputStream); } catch (IOException e) { e.printStackTrace(); } } public static String getValue(String key) { return properties.getProperty(key); } }

IRowMapper代码：

package com.jd.tool.db; import java.sql.ResultSet; public interface IRowMapper { void rowMapper(ResultSet rs); }

db.properties:

db.username = root db.password = root db.url =jdbc:mysql://127.0.0.1:3306/test