MD5加密实战

什么是MD5加密？ 一种加密手段。 为什么使用MD5进行加密？ 为了防止信息泄露，造成不必要损失。 怎样做MD5加密？ 注册登录简单实战（数据库）

项目结构

Main.java

package com.jd.test; import java.util.Scanner; import java.util.UUID; import com.jd.tool.db.DBLink; import com.jd.tool.db.MD5Tool; 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() { System.out.println("1注册");//用户名 密码 确认密码 System.out.println("2登录");//用户名 密码 System.out.println("3退出");//System.exit(0); System.out.println("请输入操作，按Enter键确认："); Scanner scanner = new Scanner(System.in); int option = scanner.nextInt(); switch (option) { case 1:{ System.out.println("欢迎使用注册系统"); 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(new DBLink().exist(sql,user_name)) { System.out.println("用户名已存在，请重新输入"); break; } System.out.println("请输入密码"); String password = scanner.next(); System.out.println("请确认密码"); String repassword = scanner.next(); if(password.equals(repassword)) { password = MD5Tool.encrypt(password); String id = UUID.randomUUID().toString(); sql = "insert into user_info(id,user_name,password) values ('"+id+"',?,?)"; if(new DBLink().update(sql,user_name,password)) { System.out.println("注册成功"); break; } } System.out.println("两次密码不一致，注册失败"); break; } case 2:{ System.out.println("欢迎使用登录系统"); System.out.println("请输入用户名"); String user_name = scanner.next(); System.out.println("请输入密码"); String password = scanner.next(); password = MD5Tool.encrypt(password); String sql = "select id from user_info where user_name=? and password=?"; if(new DBLink().exist(sql, user_name,password)) { System.out.println("登录成功"); break; } System.out.println("用户名或密码错误，登录失败"); break; } case 3:{ System.out.println("已退出系统"); System.exit(0); break; } default: System.out.println("I'm Sorry,there is not the "+option+" option,please try again."); } } }

tool

DBLink.java

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 Administrator */ public class DBLink { private Logger logger = Logger.getLogger(DBLink.class); /** * 获取数据库连接 * * @author Administrator */ 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);//创建连接 } catch (Exception e) { logger.debug(e.getMessage(), e); } return null; } /** * 查询数据 * * @author Administrator */ public void select(String sql,IRowMapper rowMapper,Object...params) {//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; PreparedStatement preparedStatement = null; ResultSet resultSet = null; try { connection = getConnection();//创建连接 preparedStatement = connection.prepareStatement(sql);//创建语句 for (int i = 0; i < params.length; i++) { preparedStatement.setObject(i+1, params[i]); } resultSet = preparedStatement.executeQuery();//executeQuery()方法会把数据库响应的查询结果存放在ResultSet类对象中供我们使用 rowMapper.IRowMapper(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 { close(resultSet,preparedStatement,connection); } } /** * 修改（insert，update和delete）数据 * * @author Administrator */ public boolean update(String sql) { Connection connection = null;//提升作用域 Statement statement = null; try { connection = getConnection(); statement = connection.createStatement(); int result = statement.executeUpdate(sql);//执行SQL语句，返回受影响的语句行数 //statement.close();//如果前面代码出错，下面代码将会不执行，所以不能写在这里 //connection.close(); return result>0; } catch (Exception e) { logger.debug(e.getMessage(), e); }finally { close(statement,connection); } return false; } /** * 修改（insert，update和delete）数据 * * @author Administrator */ public boolean update(String sql,Object...params) { Connection connection = null; PreparedStatement preparedstatement = null; try { connection = getConnection(); preparedstatement = connection.prepareStatement(sql); for (int i = 0; i < params.length; i++) { preparedstatement.setObject(i+1, params[i]); } return preparedstatement.executeUpdate()>0; } catch (Exception e) { logger.debug(e.getMessage(), e); }finally { close(preparedstatement,connection); } return false; } /** * 判断SQL语句是否能查出数据 * * @author Administrator */ public boolean exist(String sql,Object...params) {//查询 Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; try { connection = getConnection();//获取连接 preparedStatement = connection.prepareStatement(sql);//创建语句 for (int i = 0; i < params.length; i++) { preparedStatement.setObject(i, params[i]);//为占位符传值 } resultSet = preparedStatement.executeQuery(); return resultSet.next();//判断是否有值 } catch (Exception e) { logger.debug(e.getMessage(), e); }finally { close(resultSet,preparedStatement,connection); } return false; } /** * 释放资源 * * @author Administrator */ private void close(Statement statement,Connection connection) { try { if(statement!=null) { statement.close(); } } catch (SQLException e) { e.printStackTrace(); } try { if(connection!=null) { connection.close(); } } catch (SQLException e) { e.printStackTrace(); } } /** * 释放资源 * * @author Administrator */ private void close(ResultSet resultSet,Statement statement,Connection connection) {//方法的重载 try { if(resultSet!=null) { resultSet.close(); } } catch (SQLException e) { e.printStackTrace(); } close(statement,connection); } }

IRowMapper.java

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

MD5Tool.java

package com.jd.tool.db; 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; } }

PropertiesTool.java

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); } }

db.properties

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

log4j.properties

# DEBUG\u8BBE\u7F6E\u8F93\u51FA\u65E5\u5FD7\u7EA7\u522B\uFF0C\u7531\u4E8E\u4E3ADEBUG\uFF0C\u6240\u4EE5ERROR\u3001WARN\u548CINFO \u7EA7\u522B\u65E5\u5FD7\u4FE1\u606F\u4E5F\u4F1A\u663E\u793A\u51FA\u6765 log4j.rootLogger=DEBUG,Console,RollingFile #\u5C06\u65E5\u5FD7\u4FE1\u606F\u8F93\u51FA\u5230\u63A7\u5236\u53F0 log4j.appender.Console=org.apache.log4j.ConsoleAppender log4j.appender.Console.layout=org.apache.log4j.PatternLayout log4j.appender.Console.layout.ConversionPattern= [%-5p]-[%d{yyyy-MM-dd HH:mm:ss}] -%l -%m%n #\u5C06\u65E5\u5FD7\u4FE1\u606F\u8F93\u51FA\u5230\u64CD\u4F5C\u7CFB\u7EDFD\u76D8\u6839\u76EE\u5F55\u4E0B\u7684log.log\u6587\u4EF6\u4E2D log4j.appender.RollingFile=org.apache.log4j.DailyRollingFileAppender log4j.appender.RollingFile.File=D://log.log log4j.appender.RollingFile.layout=org.apache.log4j.PatternLayout log4j.appender.RollingFile.layout.ConversionPattern=%d [%t] %-5p %-40.40c %X{traceId}-%m%n

说明：

项目中使用了两次MD5加密， 第一次，注册时，密码与确认密码一致，进行加密，将密码通过MD5变为32位的字符串，传到数据库中。 第二次，登录时，将输入的密码进行加密，转换为32位的字符串，若与数据库中的32位字符串相同，即登录成功。 MD5加密保证了数据的安全性，但也不绝对安全，目前已知的MD5解码就已经达到95%的正确率了。（手动狗头）