@Transaction注解导致动态切换更改数据库失效
使用场景
- 给所有的Controller方法上加切点
- 在@Before注解的方法里,根据http请求中携带的header,动态切换数据源
- 使用mybatis或者jpa执行操作
遇到问题
当给Controller方法加上@Transaction注解后,动态切换数据源就失效了,原因是每次@Before注解的方法运行之前,protected abstract Object determineCurrentLookupKey();就已经运行了,而这个方法是切换数据源的关键。
解决
其实也算不上解决,就是不要在Controller方法上加事务注解,非要加事务,中间的Service层就不要省了。
@Transactional失效的场景及原理
1.@Transactional修饰的方法
为非public方法,这个时候@Transactional会实现。
失败的原理是:@Transactional是基于动态代理来实现的,非public的方法,他@Transactional的动态代理对象信息为空,所以不能回滚。
2.在类内部没有添加@Transactional的方法
调用了@Transactional方法时,当你调用是,他也不会回滚
测试代码如下
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@Service public class UserServiceImpl extends BaseServiceImpl<UserEntity> implements UserService { @Autowired private UserMapper userMapper; @Override @Transactional public void insertOne() { UserEntity userEntity = new UserEntity(); userEntity.setUsername( "Michael_C_2019" ); //插入到数据库 userMapper.insertSelective(userEntity); //手动抛出异常 throw new IndexOutOfBoundsException(); } @Override public void saveOne() { insertOne(); } } |
失败的原理:@Transactional是基于动态代理对象来实现的,而在类内部的方法的调用是通过this关键字来实现的,没有经过动态代理对象,所以事务回滚失效。
3.就是在@Transactional方法内部捕获了异常
没有在catch代码块里面重新抛出异常,事务也不会回滚。
代码如下:
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@Override @Transactional public void insertOne() { try { UserEntity userEntity = new UserEntity(); userEntity.setUsername( "Michael_C_2019" ); //插入到数据库 userMapper.insertSelective(userEntity); //手动抛出异常 throw new IndexOutOfBoundsException(); } catch (IndexOutOfBoundsException e) { e.printStackTrace(); } } |
所以在阿里巴巴的Java开发者手册里面有明确规定,在 @Transactional的方法里面捕获了异常,必须要手动回滚,
代码如下:
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@Override @Transactional public void insertOne() { try { UserEntity userEntity = new UserEntity(); userEntity.setUsername( "Michael_C_2019" ); //插入到数据库 userMapper.insertSelective(userEntity); //手动抛出异常 throw new IndexOutOfBoundsException(); } catch (IndexOutOfBoundsException e) { e.printStackTrace(); TransactionAspectSupport.currentTransactionStatus().setRollbackOnly(); } } |
失败原理:这时候我们来看看spring的源码:
TransactionAspectSupport类里面的invokeWithinTransaction方法
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TransactionAspectSupport |
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@Nullable protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targetClass, TransactionAspectSupport.InvocationCallback invocation) throws Throwable { TransactionAttributeSource tas = this .getTransactionAttributeSource(); TransactionAttribute txAttr = tas != null ? tas.getTransactionAttribute(method, targetClass) : null ; PlatformTransactionManager tm = this .determineTransactionManager(txAttr); String joinpointIdentification = this .methodIdentification(method, targetClass, txAttr); Object result; if (txAttr != null && tm instanceof CallbackPreferringPlatformTransactionManager) { TransactionAspectSupport.ThrowableHolder throwableHolder = new TransactionAspectSupport.ThrowableHolder( null ); try { result = ((CallbackPreferringPlatformTransactionManager)tm).execute(txAttr, (status) -> { TransactionAspectSupport.TransactionInfo txInfo = this .prepareTransactionInfo(tm, txAttr, joinpointIdentification, status); Object var9; try { Object var8 = invocation.proceedWithInvocation(); return var8; } catch (Throwable var13) { if (txAttr.rollbackOn(var13)) { if (var13 instanceof RuntimeException) { throw (RuntimeException)var13; } throw new TransactionAspectSupport.ThrowableHolderException(var13); } throwableHolder.throwable = var13; var9 = null ; } finally { this .cleanupTransactionInfo(txInfo); } return var9; }); if (throwableHolder.throwable != null ) { throw throwableHolder.throwable; } else { return result; } } catch (TransactionAspectSupport.ThrowableHolderException var19) { throw var19.getCause(); } catch (TransactionSystemException var20) { if (throwableHolder.throwable != null ) { this .logger.error( "Application exception overridden by commit exception" , throwableHolder.throwable); var20.initApplicationException(throwableHolder.throwable); } throw var20; } catch (Throwable var21) { if (throwableHolder.throwable != null ) { this .logger.error( "Application exception overridden by commit exception" , throwableHolder.throwable); } throw var21; } } else { TransactionAspectSupport.TransactionInfo txInfo = this .createTransactionIfNecessary(tm, txAttr, joinpointIdentification); result = null ; try { result = invocation.proceedWithInvocation(); } catch (Throwable var17) { //异常时,在catch逻辑中回滚事务 this .completeTransactionAfterThrowing(txInfo, var17); throw var17; } finally { this .cleanupTransactionInfo(txInfo); } this .commitTransactionAfterReturning(txInfo); return result; } } |
他是通过捕获异常然后在catch里面进行事务的回滚的,所以如果你在自己的方法里面catch了异常,catch里面没有抛出新的异常,那么事务将不会回滚。
以上为个人经验,希望能给大家一个参考,也希望大家多多支持服务器之家。
原文链接:https://blog.csdn.net/m0_37659871/article/details/81672373