关于@Transactional注解：
添加事务注解
1.使用 propagation 指定事务的传播行为, 即当前的事务方法被另外一个事务方法调用时
如何使用事务, 默认取值为 REQUIRED, 即使用调用方法的事务
REQUIRES_NEW: 事务自己的事务, 调用的事务方法的事务被挂起.
2.使用 isolation 指定事务的隔离级别, 最常用的取值为 READ_COMMITTED
3.默认情况下 Spring 的声明式事务对所有的运行时异常进行回滚. 也可以通过对应的
属性进行设置. 通常情况下去默认值即可.
4.使用 readOnly 指定事务是否为只读. 表示这个事务只读取数据但不更新数据,
这样可以帮助数据库引擎优化事务. 若真的事一个只读取数据库值的方法, 应设置 readOnly=true
5.使用 timeout 指定强制回滚之前事务可以占用的时间。
个人疑问有一些，结尾来说，用教程例子来说吧。
我的代码如下：
BookShopDao接口
package com.demo.spring.bean; public interface BookShopDao { // 根据书的编号返回书的单价 public int findBookPriceByIsbn(String isbn); // 根据书的编号返回输的库存 public void updateBookStock(String isbn); // 更新用户账户余额 public void updateUserAccount(String username, int price); }
实现类
package com.demo.spring.bean; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.stereotype.Repository; @Repository("bookShopDao") public class BookShopDaoImpl implements BookShopDao { @Autowired private JdbcTemplate jdbcTemplate; @Override public int findBookPriceByIsbn(String isbn) { // TODO Auto-generated method stub String sql = "SELECT price FROM book WHERE isbn=?"; Integer price = jdbcTemplate.queryForObject(sql, Integer.class, isbn); return price; } @Override public void updateBookStock(String isbn) { // TODO Auto-generated method stub String sql = "SELECT stock FROM book_stock WHERE isbn= ? "; Integer stock = jdbcTemplate.queryForObject(sql, Integer.class, isbn); if (stock == 0) { throw new BookStockException("库存不足！！"); } String sql1 = "UPDATE book_stock SET stock=stock-1 WHERE isbn=?"; jdbcTemplate.update(sql1, isbn); } @Override public void updateUserAccount(String username, int price) { // TODO Auto-generated method stub String sql1 = "SELECT balance FROM account WHERE username= ? "; Integer account = jdbcTemplate.queryForObject(sql1, Integer.class, username); if (account < price) { throw new AccountException("余额不足！！"); } String sql = "UPDATE account SET balance=balance-? WHERE username=?"; jdbcTemplate.update(sql, price, username); } }
BookShopService接口
package com.demo.spring.bean; public interface BookShopService { // 购书 public void purchase(String username, String isbn); }
实现类
package com.demo.spring.bean; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import org.springframework.transaction.annotation.Transactional; @Service("bookShopService") public class BookShopServiceImpl implements BookShopService { @Autowired private BookShopDao bookShopDao; // @Transactional(propagation=Propagation.REQUIRES_NEW,isolation=Isolation.READ_COMMITTED,readOnly=true,timeout=5,noRollbackFor=AccountException.class) @Transactional @Override public void purchase(String username, String isbn) { try { Thread.sleep(5000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } // TODO Auto-generated method stub int price = bookShopDao.findBookPriceByIsbn(isbn); bookShopDao.updateBookStock(isbn); bookShopDao.updateUserAccount(username, price); } }
Cashier批量购书接口
package com.demo.spring.bean; import java.util.List; public interface Cashier { // 批量购书 public void checkout(String username, List<String> isbns); }
实现类
package com.demo.spring.bean; import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service("cashier") public class CashierImpl implements Cashier { @Autowired private BookShopService bookShopService; // @Transactional @Override public void checkout(String username, List<String> isbns) { // TODO Auto-generated method stub for (String isbn : isbns) { bookShopService.purchase(username, isbn); } } }
账户余额不足及库存不足异常（自定义异常）
package com.demo.spring.bean; public class AccountException extends RuntimeException { /** * */ private static final long serialVersionUID = 1L; public AccountException() { super(); // TODO Auto-generated constructor stub } public AccountException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) { super(message, cause, enableSuppression, writableStackTrace); // TODO Auto-generated constructor stub } public AccountException(String message, Throwable cause) { super(message, cause); // TODO Auto-generated constructor stub } public AccountException(String message) { super(message); // TODO Auto-generated constructor stub } public AccountException(Throwable cause) { super(cause); // TODO Auto-generated constructor stub } }
package com.demo.spring.bean; public class BookStockException extends RuntimeException { /** * */ private static final long serialVersionUID = 1L; public BookStockException() { super(); // TODO Auto-generated constructor stub } public BookStockException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) { super(message, cause, enableSuppression, writableStackTrace); // TODO Auto-generated constructor stub } public BookStockException(String message, Throwable cause) { super(message, cause); // TODO Auto-generated constructor stub } public BookStockException(String message) { super(message); // TODO Auto-generated constructor stub } public BookStockException(Throwable cause) { super(cause); // TODO Auto-generated constructor stub } }
测试类
package com.demo.spring.bean; import java.util.Arrays; import org.junit.Test; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainTest { private ApplicationContext ctx; @Autowired private Cashier cashier; { ctx=new ClassPathXmlApplicationContext("bean.xml"); cashier=(Cashier) ctx.getBean("cashier"); } @Test public void test(){ // System.out.println(bookShopDao.findBookPriceByIsbn("1001")); cashier.checkout("rongrong", Arrays.asList("1001","1002")); } }
bean文件
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.1.xsd"> <!-- 装载自导导入的包 --> <context:component-scan base-package="com.demo.spring.bean"></context:component-scan> <!-- 引入外部数据源 --> <context:property-placeholder location="classpath:db.properties"/> <!-- 配置mysql数据源 --> <bean id="datasource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="${db.driverClassName}"></property> <property name="url" value="${db.url}"></property> <property name="username" value="${db.username}"></property> <property name="password" value="${db.password}"></property> </bean> <!-- 配置jdbc模板 --> <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"> <property name="dataSource" ref="datasource"></property> </bean> <!-- 配置事务管理器 --> <bean id="transactionManagertest" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="datasource"></property> </bean> <!-- 启用事务注解 --> <tx:annotation-driven transaction-manager="transactionManagertest"/> </beans>
数据源
db.driverClassName=com.mysql.jdbc.Driver db.url=jdbc:mysql://localhost:3306/spring db.username=root db.password=root
疑问如下：
前提条件：用户按照1001，1002这种顺序去购书，调用checkout接口批量购书
@Transactional注解确实满足原子性操作，要么都做，要么不做
但是，我试验了下，如果在public void checkout(String username, List<String> isbns) 上方不加Transactional
与在public void purchase(String username, String isbn)上方加@Transactional(propagation=Propagation.REQUIRES_NEW效果一样
当账户余额为120，可以满足账户减去1001的单价，1001的库存减1
但是，将账户余额改为80，从单价上看可以买1002那本书，按照上面的顺序去买书
按照上面加上注解@Transactional(propagation=Propagation.REQUIRES_NEW效果一样，根本不好使，
我个人觉得因为在更新账户余额，那有个判断先查询1001的书的单价确实大于当前账户余额80，先判断了，所以抛异常后面代码就不走了
另外当前账户余额可以买1002这本书，想在不改变购书的顺序情况下，用@Transactional注解实现，可以买1002这本书？，减去当前账户余额80，更新1002书的库存，哪位大神看到，帮我看下，怎么用这个注解实现？
附上：sql
/* Navicat MySQL Data Transfer Source Server : myTestdata Source Server Version : 50627 Source Host : localhost:3306 Source Database : spring Target Server Type : MYSQL Target Server Version : 50627 File Encoding : 65001 Date: 2017-01-18 11:28:50 */ SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for account -- ---------------------------- DROP TABLE IF EXISTS `account`; CREATE TABLE `account` ( `username` varchar(50) NOT NULL, `balance` int(11) DEFAULT NULL, PRIMARY KEY (`username`) ) ENGINE=InnoDB DEFAULT CHARSET=gbk; -- ---------------------------- -- Records of account -- ---------------------------- INSERT INTO `account` VALUES ('rongrong', '300'); INSERT INTO `account` VALUES ('zhangsan', '200'); -- ---------------------------- -- Table structure for book -- ---------------------------- DROP TABLE IF EXISTS `book`; CREATE TABLE `book` ( `isbn` varchar(50) NOT NULL, `book_name` varchar(100) DEFAULT NULL, `price` int(11) DEFAULT NULL, PRIMARY KEY (`isbn`) ) ENGINE=InnoDB DEFAULT CHARSET=gbk; -- ---------------------------- -- Records of book -- ---------------------------- INSERT INTO `book` VALUES ('1001', 'java', '100'); INSERT INTO `book` VALUES ('1002', 'python', '60'); -- ---------------------------- -- Table structure for book_stock -- ---------------------------- DROP TABLE IF EXISTS `book_stock`; CREATE TABLE `book_stock` ( `isbn` varchar(50) NOT NULL, `bookname` varchar(100) DEFAULT NULL, `stock` int(11) DEFAULT NULL, PRIMARY KEY (`isbn`) ) ENGINE=InnoDB DEFAULT CHARSET=gbk; -- ---------------------------- -- Records of book_stock -- ---------------------------- INSERT INTO `book_stock` VALUES ('1001', 'java', '10'); INSERT INTO `book_stock` VALUES ('1002', 'python', '10');