使用spring的annotation配置事务

首先配置Hibernate的局部事务管理，使用HibernateTransactionManager类，该类实现了PlatformTransactionManager接口，是针对Hibernate的特定实现，如下添加：

    <bean id="transactionManager"
            class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"></property>
    </bean>

另外需要开启annotation支持，添加如下配置：

<tx:annotation-driven transaction-manager="transactionManager"/>

添加完成后我的applicationContext.xml文件如下：

<?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:p="http://www.springframework.org/schema/p"
    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-2.0.xsd
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
    <!-- derby创建用户名和密码参考：http://www.joyzhong.com/archives/643 -->
    <bean
        id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName">
            <value>org.apache.derby.jdbc.EmbeddedDriver</value>
        </property>
        <property name="url">
            <value>jdbc:derby:f:/zwh/mydb2</value>
        </property>
        <property name="username">
            <value>root</value>
        </property>
        <property name="password">
            <value>root</value>
        </property>
    </bean>
    <bean
        id="sessionFactory"
        class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
        <property name="dataSource">
            <ref bean="dataSource"/>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect"> org.hibernate.dialect.DerbyDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
            </props>
        </property>
        <property name="annotatedClasses">
            <list>
                <value>zwh.ssh.maven.po.User</value>
                <value>zwh.ssh.maven.po.Account</value>
                <value>zwh.ssh.maven.po.Book</value>
            </list>
        </property>
    </bean>
    <!-- 使用annotation的方式配置Spring Bean -->
    <context:component-scan base-package="zwh.ssh.maven"></context:component-scan>
    <!-- 使用注解方式的aop -->
    <bean class="zwh.ssh.maven.aop.ServiceAdvice"></bean>
    <bean class="zwh.ssh.maven.aop.DaoAdvice"></bean>
    <aop:aspectj-autoproxy/>
    <!-- 开启声明式事务，并采用注解的方式 -->
    <bean id="transactionManager"
            class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"></property>
    </bean>
    <tx:annotation-driven transaction-manager="transactionManager"/>
</beans>

使用事务时，只需要在某方法上使用@Transactional标注即可，例如：

@Service("accountService")
public class AccountServiceImpl implements AccountService {
	@Autowired
	private AccountDao accountDao;
	@Autowired
	private BookDao bookDao;
	
	public AccountDao getAccountDao() {
		return accountDao;
	}

	public void setAccountDao(AccountDao accountDao) {
		this.accountDao = accountDao;
	}
	
	public BookDao getBookDao() {
		return bookDao;
	}

	public void setBookDao(BookDao bookDao) {
		this.bookDao = bookDao;
	}

	@Override
	public Account getAccountByUserID(int user_id) {
		Account account = this.accountDao.getAccountByUserID(user_id);
		return account;
	}
	
	@Transactional
	@Override
	public void buyBooks(Account account, Book book, int num) {
		account.setBalance(account.getBalance() - book.getPrice()*num);
		book.setAmount(book.getAmount() - num);
		this.bookDao.update(book);
		this.accountDao.update(account);
	}
}

上面的buyBooks模拟了一次购买书的过程，在这次购书过程中需要两次与数据库交互，首先调用bookDao的update方法减少书的数量，然后调用accountDao的update方法减少账户余额。如果该过程不采用事务，假设某一次买书的过程中书的数量是充足的，而账户的余额不足，那么就会出现书的数量减少了而余额却仍是原来的余额，这肯定出问题。加上事务之后就不会出现了上面的问题了，如果这次执行中出现了异常，那么事务的全部操作都被回滚。