Spring事务失效的几种原因

1.数据库引擎不支持事务

在MySQL数据库中有几种引擎(InnoDB,MyISAM,Memory等等),仅仅InnoDB支持事务,如果数据库底层都不支持事务的话,那么再怎么折腾都是白搭.   mysql的myisam引擎不支持事务操作，innodb才支持事务。从mysql5.5.5开始的默认存储引擎是innodb 之前默认都是myisam

2.没有被spring管理

     因为事务使用的是代理类织入。如@Service注解被注解掉，则该bean不会被spring管理

 

3.方法不是public的，@transactional加在private方法上

@Transactional只能加在public方法上,如果需要在private方法中加入事务,可以使用Aspect配transactionManager使用.

4.自调用问题- 本类方法调本类另一个方法

   调用该类自己的方法，而没有经过spring的代理类，默认只有在外部调用事务才会生效。解决方案之一是在类中注入自己，用注入的对象再调用另外一个方法。另一个方案如下：

     使用两个服务类(被调用的方法也定义到一个service类里)，从ioc容器中直接获取该服务的代理对象

例如:

@Service
public class UserServiceImpl implements UserService {

  @Transactional
  public void update(User user) {
  //check
    updateUserInfo(user);
  }

  @Transactional(propagation = Propagation.REQUIRES_NEW)
  public void updateUser(User user) {
    // update user
  }

}

@Transactional(propagation = Propagation.REQUIRES_NEW)是无效的,在Spring中是使用代理的方式实现事务,发生自身调用的时候,没有经过Spring的代理,自然事务失效.

6.事务的扩展上不支持事务

     如 Propagation.NOT_SUPPORTED 表示不以事务运行，当前存在事务则挂起

@Service
public class UserServiceImpl implements UserService {

  @Transactional(propagation = Propagation.NOT_SUPPORTED)
  public void update(User user) {
  //do some action
  }

}

@Transactional(propagation = Propagation.NOT_SUPPORTED)表示如果当前存在事务就挂起,以没有事务的方式运行,主动不支持事务了,那么再怎么操作也是白搭. 此处贴下Spring的传播行为:

  /**
   * Support a current transaction, create a new one if none exists.
   * Analogous to EJB transaction attribute of the same name.
   * <p>This is the default setting of a transaction annotation.
   */
  REQUIRED(TransactionDefinition.PROPAGATION_REQUIRED),

  /**
   * Support a current transaction, execute non-transactionally if none exists.
   * Analogous to EJB transaction attribute of the same name.
   * <p>Note: For transaction managers with transaction synchronization,
   * PROPAGATION_SUPPORTS is slightly different from no transaction at all,
   * as it defines a transaction scope that synchronization will apply for.
   * As a consequence, the same resources (JDBC Connection, Hibernate Session, etc)
   * will be shared for the entire specified scope. Note that this depends on
   * the actual synchronization configuration of the transaction manager.
   * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setTransactionSynchronization
   */
  SUPPORTS(TransactionDefinition.PROPAGATION_SUPPORTS),

  /**
   * Support a current transaction, throw an exception if none exists.
   * Analogous to EJB transaction attribute of the same name.
   */
  MANDATORY(TransactionDefinition.PROPAGATION_MANDATORY),

  /**
   * Create a new transaction, and suspend the current transaction if one exists.
   * Analogous to the EJB transaction attribute of the same name.
   * <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box
   * on all transaction managers. This in particular applies to
   * {@link org.springframework.transaction.jta.JtaTransactionManager},
   * which requires the {@code javax.transaction.TransactionManager} to be
   * made available to it (which is server-specific in standard Java EE).
   * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager
   */
  REQUIRES_NEW(TransactionDefinition.PROPAGATION_REQUIRES_NEW),

  /**
   * Execute non-transactionally, suspend the current transaction if one exists.
   * Analogous to EJB transaction attribute of the same name.
   * <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box
   * on all transaction managers. This in particular applies to
   * {@link org.springframework.transaction.jta.JtaTransactionManager},
   * which requires the {@code javax.transaction.TransactionManager} to be
   * made available to it (which is server-specific in standard Java EE).
   * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager
   */
  NOT_SUPPORTED(TransactionDefinition.PROPAGATION_NOT_SUPPORTED),

  /**
   * Execute non-transactionally, throw an exception if a transaction exists.
   * Analogous to EJB transaction attribute of the same name.
   */
  NEVER(TransactionDefinition.PROPAGATION_NEVER),

  /**
   * Execute within a nested transaction if a current transaction exists,
   * behave like PROPAGATION_REQUIRED else. There is no analogous feature in EJB.
   * <p>Note: Actual creation of a nested transaction will only work on specific
   * transaction managers. Out of the box, this only applies to the JDBC
   * DataSourceTransactionManager when working on a JDBC 3.0 driver.
   * Some JTA providers might support nested transactions as well.
   * @see org.springframework.jdbc.datasource.DataSourceTransactionManager
   */
  NESTED(TransactionDefinition.PROPAGATION_NESTED);

7.异常被吃--异常被catch

     默认回滚的是RuntimeException,如果想触发其他异常回滚，需要在注解上配置一下(rollbackFor=Exception.class)

     将异常try catch 没有throw出来。回滚异常没有，无法回滚

@Service
public class UserServiceImpl implements UserService {

  @Transactional
  public void update(User user) {
  try{

  }catch(Exception e){
    log.error(e.getMessage(),e);
  }
  }

}

触发回滚的操作是被接收到异常,一般我们会在@Transactional后面加上rollbackFor或者noRollbackForClassName来指明触发回滚的异常,但是如果在代码中给catch了异常,那么对于Spring代理来说就这个方法从头到尾都没有问题,自然不会触发回滚.

8.异常类型错误

@Service
public class UserServiceImpl implements UserService {

  @Transactional
  public void update(User user) {
  try{

  }catch(Exception e){
    log.error(e.getMessage(),e);
    throw new Exception(e.getMessage());
  }
  }

}

以上方式throw new Exception(e.getMessage());事务也是无效的,主要原因是事务回滚的条件是throw 运行时异常(RunTimeException).如果需要其他异常也回滚,需要在@Transactional后面加上rollbackFor或者noRollbackForClassName来指明触发回滚的异常.

9.数据源没有配置事务管理器,没有配置TransactionManager