myBatis之事务管理

1. myBatis单独使用时，使用SqlSession来处理事务： 

public class MyBatisTxTest {

    private static SqlSessionFactory sqlSessionFactory;
    private static Reader reader;

    @BeforeClass
    public static void setUpBeforeClass() throws Exception {
        try {
            reader = Resources.getResourceAsReader("Configuration.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } finally {
            if (reader != null) {
                reader.close();
            }
        }
    }

    @Test
    public void updateUserTxTest() {
        SqlSession session = sqlSessionFactory.openSession(false); // 打开会话，事务开始

        try {
            IUserMapper mapper = session.getMapper(IUserMapper.class);
            User user = new User(9, "Test transaction");
            int affectedCount = mapper.updateUser(user); // 因后面的异常而未执行commit语句
            User user = new User(10, "Test transaction continuously");
            int affectedCount2 = mapper.updateUser(user2); // 因后面的异常而未执行commit语句
            int i = 2 / 0; // 触发运行时异常
            session.commit(); // 提交会话，即事务提交
        } finally {
            session.close(); // 关闭会话，释放资源
        }
    }
}

2. 和Spring集成后，使用Spring的事务管理： 

a. @Transactional方式： 

在类路径下创建beans-da-tx.xml文件，在beans-da.xml（系列五）的基础上加入事务配置： 

<!-- 事务管理器 -->
<bean id="txManager"
    class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
</bean>

<!-- 事务注解驱动，标注@Transactional的类和方法将具有事务性 -->
<tx:annotation-driven transaction-manager="txManager" />

<bean id="userService" class="com.john.hbatis.service.UserService" />

服务类： 

@Service("userService")
public class UserService {

    @Autowired
    IUserMapper mapper;

    public int batchUpdateUsersWhenException() { // 非事务性
        User user = new User(9, "Before exception");
        int affectedCount = mapper.updateUser(user); // 执行成功
        User user2 = new User(10, "After exception");
        int i = 1 / 0; // 抛出运行时异常
        int affectedCount2 = mapper.updateUser(user2); // 未执行
        if (affectedCount == 1 && affectedCount2 == 1) {
            return 1;
        }
        return 0;
    }

    @Transactional
    public int txUpdateUsersWhenException() { // 事务性
        User user = new User(9, "Before exception");
        int affectedCount = mapper.updateUser(user); // 因后面的异常而回滚
        User user2 = new User(10, "After exception");
        int i = 1 / 0; // 抛出运行时异常，事务回滚
        int affectedCount2 = mapper.updateUser(user2); // 未执行
        if (affectedCount == 1 && affectedCount2 == 1) {
            return 1;
        }
        return 0;
    }
}

在测试类中加入： 

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:beans-da-tx.xml" })
public class SpringIntegrateTxTest {

    @Resource
    UserService userService;

    @Test
    public void updateUsersExceptionTest() {
        userService.batchUpdateUsersWhenException();
    }

    @Test
    public void txUpdateUsersExceptionTest() {
        userService.txUpdateUsersWhenException();
    }
}

b. TransactionTemplate方式 

在beans-da-tx.xml中添加： 

<bean id="txTemplate" class="org.springframework.transaction.support.TransactionTemplate">
    <constructor-arg type="org.springframework.transaction.PlatformTransactionManager" ref="transactionManager" />
</bean>

在UserService类加入： 

@Autowired(required = false)
TransactionTemplate txTemplate;

public int txUpdateUsersWhenExceptionViaTxTemplate() {
    int retVal = txTemplate.execute(new TransactionCallback<Integer>() {

        @Override
        public Integer doInTransaction(TransactionStatus status) { // 事务操作
            User user = new User(9, "Before exception");
            int affectedCount = mapper.updateUser(user); // 因后面的异常而回滚
            User user2 = new User(10, "After exception");
            int i = 1 / 0; // 抛出运行时异常并回滚
            int affectedCount2 = mapper.updateUser(user2); // 未执行
            if (affectedCount == 1 && affectedCount2 == 1) {
                return 1;
            }
            return 0;
        }

    });
    return retVal;
}

在SpringIntegrateTxTest类中加入： 

@Test
public void updateUsersWhenExceptionViaTxTemplateTest() {
    userService.txUpdateUsersWhenExceptionViaTxTemplate(); //
}

注：不可catch Exception或RuntimeException而不抛出： 

@Transactional
public int txUpdateUsersWhenExceptionAndCatch() { // 事务性操作，但是外围框架捕获不到异常，认为执行正确而提交。
    try {
        User user = new User(9, "Before exception");
        int affectedCount = mapper.updateUser(user); // 执行成功
        User user2 = new User(10, "After exception");
        int i = 1 / 0; // 抛出运行时异常
        int affectedCount2 = mapper.updateUser(user2); // 未执行
        if (affectedCount == 1 && affectedCount2 == 1) {
            return 1;
        }
    } catch (Exception e) { // 所有异常被捕获而未抛出
        e.printStackTrace();
    }
    return 0;
}