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1 Service
什么是业务?
代表用户完成的一个业务功能#xff0c;可以由一个或多个DAO的调用组成。软件所提供的一个功…JDBC 结构优化2 文章目录 JDBC 结构优化2结构优化2 - ATM系统(存,取,转,查)1 Service2 事务3 ThreadLocal4 事务的封装 结构优化2 - ATM系统(存,取,转,查)
1 Service
什么是业务?
代表用户完成的一个业务功能可以由一个或多个DAO的调用组成。软件所提供的一个功能叫业务。
核心思想: 用户角度: 功能即业务 转账这一功能就是一个业务 服务者角度: 业务包含多个步骤 从A账户扣钱给B账户加钱 程序设计角度: 每一个步骤都是一个方法 AccountDao save() //存钱take() //取钱 AccountService transfer(){dao.take(A);dao.save(B);
}**目的**DAO提高数据操作的重用性Service提高业务功能的重用性。
2 事务
概念
事务是一个原子操作由一个或多个SQL语句组成。在同一个事务当中所有的SQL语句要么全部执行成功要么全部失败。
事务的边界
在JDBC中先获得Connection对象。开始事务conn.setAutoCommit(false); #set autocommit0;手动提交事务conn.commit(); #commit手动回滚事务conn.rollback(); #rollback;
在Service中调用了多次DAO操作。每一个业务功能都要控制事务。
在Service层中控制事务 问题: 当程序发生异常事务回滚并没有成功。
原因Service控制事务和DAO访问数据库时的连接对象并非同一个 注意: 在一个业务流程中要保证多个数据库访问操作的连接对象是同一个。
解决方法:
可以将整个线程中单线程中存储一个共享值。线程拥有一个类似Map的属性键值对结构ThreadLocal对象值。
3 ThreadLocal
ThreadLocal线程本地变量
每一个线程通过ThreadLocal绑定一个连接对象。在整个流程中任一环节可以存值或取值。
ThreadLocal应用流程 ThreadLocal应用 在释放资源的方法中连接对象关闭后提供threadLocal.remove()。 将关闭后的连接从当前ThreadLocal中移除。
4 事务的封装
现有问题
事务的开启、提交、回滚的代码都写在了Service中。Service的主要职责是模拟现实业务功能。要将事务的控制封装在工具类中。
工具类封装事务控制方法
开启事务begin();
代码演示:
// 4 开启事务
public static void begin() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.setAutoCommit(false);}
}提交事务commit();
代码演示:
// 5 提交事务
public static void commit() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.commit();}
}回滚事务rollback();
代码演示:
// 6 回滚事务
public static void rollback() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.rollback();}
}关闭连接close(); 解除绑定连接
代码演示:
// 3 释放资源
public static void closeAll(Connection connection, Statement statement, ResultSet resultSet) {try {if (resultSet ! null) {resultSet.close();}if (statement ! null) {statement.close();}if (connection ! null) {//判断是否开启事务, 如果没有开启事务, 要关闭//若开启事务, 则在事务结束后手动关闭if (connection.getAutoCommit()) {connection.close();//从线程中移除threadLocal.remove();}}} catch (SQLException e) {System.out.println(资源释放失败: e.getMessage());throw new RuntimeException(e);}
}// 7 关闭事务连接
public static void close() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.close();threadLocal.remove();}
}ATM系统
代码演示:
Dao层
Dao接口:
public interface AccountDao {//查询Account select(String cardNo, String password);Account select(String cardNo);//更新//更新存钱void updateSave(String cardNo, BigDecimal money);//更新取钱void updateTake(String cardNo, BigDecimal money);//更新密码void updatePassword(String cardNo, String password);
}DaoImpl:
public class AccountDaoImpl implements AccountDao {//登录Overridepublic Account select(String cardNo, String password) {ResultSet resultSet null;PreparedStatement preparedStatement null;Connection connection null;try {// 1 获取连接connection DBUtils.getConnection();// 2 创建预编译命令String sql SELECT * FROM companydb.account where cardNo ? And password ?;preparedStatement connection.prepareStatement(sql);// 给?占位符赋值preparedStatement.setObject(1, cardNo);preparedStatement.setObject(2, password);// 3 执行命令resultSet preparedStatement.executeQuery();Account account null;// 4 处理if (resultSet.next()) {int id resultSet.getInt(id);String name resultSet.getString(name);BigDecimal money resultSet.getBigDecimal(money);account new Account(id, name, money, cardNo, password);}return account;} catch (SQLException e) {throw new RuntimeException(e);} finally {// 5 释放资源DBUtils.closeAll(connection, preparedStatement, resultSet);}}//通过卡号查询Overridepublic Account select(String cardNo) {ResultSet resultSet null;PreparedStatement preparedStatement null;Connection connection null;try {// 1 获取连接connection DBUtils.getConnection();// 2 创建预编译命令String sql SELECT * FROM companydb.account where cardNo ?;preparedStatement connection.prepareStatement(sql);// 参数赋值preparedStatement.setObject(1, cardNo);// 3 执行命令resultSet preparedStatement.executeQuery();Account account null;// 4 处理(获取结果集中的数据)if (resultSet.next()) {int id resultSet.getInt(id);String name resultSet.getString(name);BigDecimal money resultSet.getBigDecimal(money);String password resultSet.getString(password);account new Account(id, name, money, cardNo, password);}return account;} catch (SQLException e) {throw new RuntimeException(e);} finally {//关闭资源DBUtils.closeAll(connection, preparedStatement, resultSet);}}//存钱Overridepublic void updateSave(String cardNo, BigDecimal money) {Connection connection null;PreparedStatement preparedStatement null;try {//1 获取连接connection DBUtils.getConnection();//2 创建预编译SQL命令String sql UPDATE companydb.account SET account.money account.money ? WHERE account.cardNo ?;preparedStatement connection.prepareStatement(sql);//2.1 参数赋值preparedStatement.setObject(1, money);preparedStatement.setObject(2, cardNo);//3 执行命令preparedStatement.executeUpdate();} catch (SQLException e) {throw new RuntimeException(e);} finally {//4 释放资源DBUtils.closeAll(connection, preparedStatement, null);}}//取钱Overridepublic void updateTake(String cardNo, BigDecimal money) {Connection connection null;PreparedStatement preparedStatement null;try {//1 获取连接connection DBUtils.getConnection();//2 创建预编译SQL命令String sql UPDATE companydb.account SET account.money account.money - ? WHERE account.cardNo ?;preparedStatement connection.prepareStatement(sql);//2.1 参数赋值preparedStatement.setObject(1, money);preparedStatement.setObject(2, cardNo);//3 执行命令/处理preparedStatement.executeUpdate();} catch (SQLException e) {throw new RuntimeException(e);} finally {//释放资源DBUtils.closeAll(connection, preparedStatement, null);}}//修改密码Overridepublic void updatePassword(String cardNo, String password) {Connection connection null;PreparedStatement preparedStatement null;try {//1 获取连接connection DBUtils.getConnection();String sql UPDATE companydb.account SET account.password ? WHERE account.cardNo ?;//2 创建预编译SQL命令preparedStatement connection.prepareStatement(sql);//2.1 参数赋值preparedStatement.setObject(1, password);preparedStatement.setObject(2, cardNo);//3 执行命令/处理preparedStatement.executeUpdate();} catch (SQLException e) {throw new RuntimeException(e);} finally {//4 释放资源DBUtils.closeAll(connection, preparedStatement, null);}}
}entity
Account:
public class Account {private Integer id;private String name;private BigDecimal money;private String cardNo;private String password;public Account() {}public Account(Integer id, String name, BigDecimal money, String cardNo, String password) {this.id id;this.name name;this.money money;this.cardNo cardNo;this.password password;}public Integer getId() {return id;}public void setId(Integer id) {this.id id;}public String getName() {return name;}public void setName(String name) {this.name name;}public BigDecimal getMoney() {return money;}public void setMoney(BigDecimal money) {this.money money;}public String getCardNo() {return cardNo;}public void setCardNo(String cardNo) {this.cardNo cardNo;}public String getPassword() {return password;}public void setPassword(String password) {this.password password;}
}service层
service接口:
public interface AccountService {//登录Account login(String cardNo, String password);//存钱void save(String cardNo, BigDecimal money);//取钱void take(String cardNo, BigDecimal money);//转账void trans(String from, String to, BigDecimal money);//查询余额Account queryMoney(String cardNo, String password);//修改密码void modifyPassword(String cardNo, String oldPwd, String newPwd);
}serviceImpl:
public class AccountServiceImpl implements AccountService {//声明数据访问对象, 以调用Dao层操作private static final AccountDaoImpl accountDao new AccountDaoImpl();//登录public Account login(String cardNo, String password) {//通过卡号和密码查询数据, 都正确时放回数据, 登录成功Account account accountDao.select(cardNo, password);if (account null) {throw new RuntimeException(账户或密码错误);}return account;}//存钱public void save(String cardNo, BigDecimal money) {//添加限制//因money是BigDecimal类型, 使用compareTo方法进行比较//通过相减的方式进行比较判断if (money.compareTo(new BigDecimal(0))0) {throw new RuntimeException(存款金额必须大于0);}if (money.compareTo(new BigDecimal(50000))0) {throw new RuntimeException(存款金额必须小于50000);}accountDao.updateSave(cardNo, money);}//取款public void take(String cardNo, BigDecimal money) {if (money.compareTo(new BigDecimal(0))0) {throw new RuntimeException(取款金额必须大于0);}if (money.compareTo(new BigDecimal(20000))0) {throw new RuntimeException(取款金额必须小于20000);}//通过卡号查询当前账户的余额Account account accountDao.select(cardNo);if (money.compareTo(account.getMoney())0) {throw new RuntimeException(账户余额不足...);}accountDao.updateTake(cardNo, money);}//转账public void trans(String from, String to, BigDecimal money) {if (money.compareTo(new BigDecimal(0))0) {throw new RuntimeException(转账金额必须大于0);}if (money.compareTo(new BigDecimal(20000))0) {throw new RuntimeException(转账金额必须小于20000);}//通过卡号查询转账账户的余额Account account accountDao.select(from);if (money.compareTo(account.getMoney())0) {throw new RuntimeException(账户余额不足...);}//判断转账双方是否是同一人if (from.equals(to)) {throw new RuntimeException(不能给自己转账...);}//通过卡号查询判断接收方是否存在if (accountDao.select(to) null) {throw new RuntimeException(对方账户不存在...);}//转账try {//开启事务, 调用线程中的连接DBUtils.begin();//使用同一连接accountDao.updateTake(from, money);accountDao.updateSave(to, money);DBUtils.commit();//手动提交} catch (Exception e) {try {DBUtils.rollback();//异常回滚} catch (SQLException ex) {e.printStackTrace();}throw new RuntimeException(e);} finally {//手动关闭try {DBUtils.close();//关闭事务连接} catch (SQLException e) {e.printStackTrace();}}}//查询余额public Account queryMoney(String cardNo, String password) {AccountDao accountDao new AccountDaoImpl();Account account accountDao.select(cardNo, password);if (accountnull) {throw new RuntimeException(密码有误);}return account;}//修改密码public void modifyPassword(String cardNo, String oldPwd, String newPwd) {AccountDao accountDao new AccountDaoImpl();Account account accountDao.select(cardNo,oldPwd);if (account null) {throw new RuntimeException(原始密码有误...);}if (oldPwd.equals(newPwd)) {throw new RuntimeException(新密码不能与原始密码相同);}accountDao.updatePassword(cardNo,newPwd);}
}test:
ATMSystem:
public class ATMSystem {public static void main(String[] args) {Scanner scanner new Scanner(System.in);System.out.println(请输入卡号);String cardNo scanner.next();System.out.println(请输入密码);String password scanner.next();//创建业务对象AccountService accountService new AccountServiceImpl();try {Account account accountService.login(cardNo, password);boolean flag true;System.out.println(登录成功, 欢迎: account.getName());do {System.out.println(1 存钱, 2 取钱, 3 转账, 4 查询余额, 5 修改密码, 0 退出);System.out.println(请选择:);int choose scanner.nextInt();switch (choose) {case 1:try {System.out.println(请输入存钱金额:);BigDecimal money scanner.nextBigDecimal();accountService.save(account.getCardNo(), money);System.out.println(存钱成功...);} catch (Exception e) {System.out.println(e.getMessage());}break;case 2:try {System.out.println(请输入取款金额:);BigDecimal money scanner.nextBigDecimal();accountService.take(account.getCardNo(), money);System.out.println(取款成功...);} catch (Exception e) {System.out.println(e.getMessage());}break;case 3:System.out.println(请输入对方的卡号:);String toCard scanner.next();System.out.println(请输入转账金额:);BigDecimal money scanner.nextBigDecimal();try {accountService.trans(account.getCardNo(),toCard,money);System.out.println(转账成功...);} catch (Exception e) {System.out.println(e.getMessage());}break;case 4:System.out.println(请输入密码:);String pwd scanner.next();try {System.out.println(当前账户余额为: accountService.queryMoney(account.getCardNo(), pwd).getMoney());} catch (Exception e) {System.out.println(e.getMessage());}break;case 5:System.out.println(请输入原始密码);String oldPwd scanner.next();System.out.println(请输入新密码);String newPwd scanner.next();System.out.println(请再次输入新密码);String againPwd scanner.next();if (newPwd.equals(againPwd)) {try {accountService.modifyPassword(account.getCardNo(), oldPwd, newPwd);System.out.println(密码修改成功...);} catch (Exception e) {System.out.println(e.getMessage());}} else {System.out.println(两次密码不一致...);}break;case 0:flag false;break;default:System.out.println(输入有误...);}} while (flag);System.out.println(欢迎下次光临...);} catch (Exception e) {System.out.println(e.getMessage());}}
}util工具类
DbUtils:
public class DBUtils {private static String url;private static String user;private static String pwd;private static final ThreadLocalConnection threadLocal new ThreadLocal();// 1 注册驱动static {try {// 读取属性配置文件Properties properties new Properties();FileInputStream fis new FileInputStream(Properties/db.properties);properties.load(fis);fis.close();// 变量赋值String driver properties.getProperty(driver);url properties.getProperty(url);user properties.getProperty(user);pwd properties.getProperty(pwd);// 获取驱动对象Class.forName(com.mysql.jdbc.Driver);} catch (Exception e) {System.out.println(注册驱动失败: e.getMessage());}}// 2 获取连接public static Connection getConnection() {try {//从线程中获取连接Connection connection threadLocal.get();//判断线程中是否有连接, 没有则从数据库中获取if (connection null) {connection DriverManager.getConnection(url,user,pwd);//将连接放入线程中threadLocal.set(connection);}//若线程中有连接, 则直接返回return connection;} catch (SQLException e) {throw new RuntimeException(e);}}// 3 释放资源public static void closeAll(Connection connection, Statement statement, ResultSet resultSet) {try {if (resultSet ! null) {resultSet.close();}if (statement ! null) {statement.close();}if (connection ! null) {//判断是否开启事务, 如果没有开启事务, 要关闭//若开启事务, 则在事务结束后手动关闭if (connection.getAutoCommit()) {connection.close();//从线程中移除threadLocal.remove();}}} catch (SQLException e) {System.out.println(资源释放失败: e.getMessage());throw new RuntimeException(e);}}// 4 开启事务public static void begin() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.setAutoCommit(false);}}// 5 提交事务public static void commit() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.commit();}}// 6 回滚事务public static void rollback() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.rollback();}}// 7 关闭事务连接public static void close() throws SQLException{Connection connection DBUtils.getConnection();if (connection ! null) {connection.close();threadLocal.remove();}}
}
