Spring 声明事务中transactionAttributes属性 + - Exception 实现逻辑
下面是一段典型的Spring 声明事务的配置：
1 <bean id=“baseTxProxy” lazy-init=“true”class=“org.springframework.transaction.interceptor.TransactionProxyFactoryBean” scope=“singleton” abstract=“true”> 2 <property name=“transactionManager”> 3 <ref local=“transactionManager” /> 4 </property> 5 <property name=“transactionAttributes”> 6 <props> 7 <prop key=“register*”>PROPAGATION_REQUIRED</prop> 8 <prop key=“trade*”>PROPAGATION_REQUIRED</prop> 9 <prop key=“cancel*”>PROPAGATION_REQUIRED</prop> 10 <prop key="save*">PROPAGATION_REQUIRED,-ApplicationException,+BusinessException</prop> 11 <prop key=“exe*”>PROPAGATION_REQUIRED</prop> 12 <prop key=“add*”>PROPAGATION_REQUIRED</prop> 13 <prop key=“persist*”>PROPAGATION_REQUIRED</prop> 14 <prop key=“remove*”>PROPAGATION_REQUIRED</prop> 15 <prop key=“del*”>PROPAGATION_REQUIRED</prop> 16 <prop key=“update*”>PROPAGATION_REQUIRED</prop> 17 <prop key=“gen*”>PROPAGATION_REQUIRED</prop> 18 <prop key=“finish*”>PROPAGATION_REQUIRED</prop> 19 <prop key=“get*”>PROPAGATION_REQUIRED,readOnly</prop> 20 <prop key=“find*”>PROPAGATION_REQUIRED,readOnly</prop> 21 <prop key=“query*”>PROPAGATION_REQUIRED,readOnly</prop> 22 <prop key=“select*”>PROPAGATION_REQUIRED,readOnly</prop> 23 <prop key=“is*”>PROPAGATION_REQUIRED,readOnly</prop> 24 </props> 25 </property> 26 </bean>
查阅相关spring 的资料后发现transactionAttributes的各种属性的意义如下：
PROPAGATION_REQUIRED--支持当前事务，如果当前没有事务，就新建一个事务。这是最常见的选择。
PROPAGATION_SUPPORTS--支持当前事务，如果当前没有事务，就以非事务方式执行。
PROPAGATION_MANDATORY--支持当前事务，如果当前没有事务，就抛出异常。
PROPAGATION_REQUIRES_NEW--新建事务，如果当前存在事务，把当前事务挂起。
PROPAGATION_NOT_SUPPORTED--以非事务方式执行操作，如果当前存在事务，就把当前事务挂起。
PROPAGATION_NEVER--以非事务方式执行，如果当前存在事务，则抛出异常。
PROPAGATION_NESTED--如果当前存在事务，则在嵌套事务内执行。如果当前没有事务，则进行与PROPAGATION_REQUIRED类似的操作。
在Spring声明事务中，我们可以自定义方法的哪些Exception需要回滚，哪些Exception可以直接提交。
通过下面的配置：
<prop key="save*">PROPAGATION_REQUIRED,-aplicationException,+BusinessException</prop>
- 表示抛出该异常时需要回滚
+表示即使抛出该异常事务同样要提交
-ApplicationException ：表示抛出ApplicationException 时，事务需要回滚。但不是说只抛出ApplicationException 异常时，事务才回滚，如果程序抛出RuntimeException和Error时，事务一样会回滚，即使这里没有配置。因为Spring中默认对所有的RuntimeException和Error都会回滚事务。
Spring中是如何实现这段逻辑的：
调用的是
org.springframework.transaction.interceptor.RuleBasedTransactionAttribute.rollbackOn(Throwable ex)
1 public boolean rollbackOn(Throwable ex) { 2 if (logger.isTraceEnabled()) { 3 logger.trace("Applying rules to determine whether transaction should rollback on " + ex); 4 } 5 6 RollbackRuleAttribute winner = null; 7 int deepest = Integer.MAX_VALUE; 8 9 //配置文件中的回滚异常列表，当然去掉了-，只有name，commit的规则是另外一个对象 10 if (this.rollbackRules != null) { 11 for (RollbackRuleAttribute rule : this.rollbackRules) { 12 //使用抛出exception的className(全路径className)进行indexOf match 13 //如果没有match上会继续搜索superClass name进行match，到Throwable class为止 14 int depth = rule.getDepth(ex); 15 if (depth >= 0 && depth < deepest) { 16 deepest = depth; 17 winner = rule; 18 } 19 } 20 } 21 22 if (logger.isTraceEnabled()) { 23 logger.trace("Winning rollback rule is: " + winner); 24 } 25 26 // User superclass behavior (rollback on unchecked) if no rule matches. 27 if (winner == null) { 28 logger.trace("No relevant rollback rule found: applying default rules"); 29 //如果没有match上，调用此方法继续match，判断instance of RuntimeException or Error 30 return super.rollbackOn(ex); 31 } 32 33 return !(winner instanceof NoRollbackRuleAttribute); 34 }
rule.getDepth方法代码
因为使用的是className的全路径进行indexOf匹配，所以如果自定义异常是：com.abc.ApplicationException，你在xml配置文件中定义为：-abc，同样会match上，事务也会回滚，这一点需要注意。
另外一点，如何在xml中定义的是-Exception，这样只要class的全路径中包含Exception字段，如包名，也会匹配上。
1 public int getDepth(Throwable ex) { 2 return getDepth(ex.getClass(), 0); 3 } 4 5 6 private int getDepth(Class exceptionClass, int depth) { 7 if (exceptionClass.getName().indexOf(this.exceptionName) != -1) { 8 // Found it! 9 return depth; 10 } 11 // If we've gone as far as we can go and haven't found it... 12 if (exceptionClass.equals(Throwable.class)) { 13 return -1; 14 } 15 return getDepth(exceptionClass.getSuperclass(), depth + 1); 16 }
super.rollbackOn(Throwable ex) 方法代码
很简单的一行代码，这就是为什么RuntimeException和Error也会回滚啦。
1 public boolean rollbackOn(Throwable ex) { 2 return (ex instanceof RuntimeException || ex instanceof Error); 3 }
几次测试输出的debug日志：
[08/24 03:35:39] [DEBUG] RuleBasedTransactionAttribute: Applying rules to determine whether transaction should rollback on usertest.exception.BusinessException: Error
[08/24 03:35:39] [DEBUG] RuleBasedTransactionAttribute: Winning rollback rule is: RollbackRuleAttribute with pattern [BusinessException]
[08/24 03:35:39] [DEBUG] DataSourceTransactionManager: Triggering beforeCompletion synchronization
[08/24 03:35:39] [DEBUG] DataSourceTransactionManager: Initiating transaction rollback
[08/24 03:35:39] [DEBUG] DataSourceTransactionManager: Rolling back JDBC transaction on Connection [org.apache.commons.dbcp.PoolableConnection@1db05b2]
[08/24 03:35:39] [DEBUG] DataSourceTransactionManager: Triggering afterCompletion synchronization
[08/24 03:35:39] [DEBUG] TransactionSynchronizationManager: Clearing transaction synchronization
[08/24 03:35:39] [DEBUG] TransactionSynchronizationManager: Removed value [org.springframework.jdbc.datasource.ConnectionHolder@1833eca] for key [org.apache.commons.dbcp.BasicDataSource@4aa0ce] from thread [main]
[08/24 03:35:39] [DEBUG] DataSourceTransactionManager: Releasing JDBC Connection [org.apache.commons.dbcp.PoolableConnection@1db05b2] after transaction
[08/24 03:35:39] [DEBUG] DataSourceUtils: Returning JDBC Connection to DataSource
[08/24 03:39:16] [DEBUG] TransactionInterceptor: Completing transaction for [usertest.dao.UsersDAO.testInsertAndUpdate] after exception: java.lang.Exception: Error
[08/24 03:39:16] [DEBUG] RuleBasedTransactionAttribute: Applying rules to determine whether transaction should rollback on java.lang.Exception: Error
[08/24 03:39:16] [DEBUG] RuleBasedTransactionAttribute: Winning rollback rule is: null
[08/24 03:39:16] [DEBUG] RuleBasedTransactionAttribute: No relevant rollback rule found: applying superclass default
[08/24 03:39:16] [DEBUG] DataSourceTransactionManager: Triggering beforeCommit synchronization
[08/24 03:39:16] [DEBUG] DataSourceTransactionManager: Triggering beforeCompletion synchronization
[08/24 03:39:16] [DEBUG] DataSourceTransactionManager: Initiating transaction commit
[08/24 03:39:16] [DEBUG] DataSourceTransactionManager: Committing JDBC transaction on Connection [org.apache.commons.dbcp.PoolableConnection@1db05b2]
[08/24 03:39:16] [DEBUG] DataSourceTransactionManager: Triggering afterCommit synchronization
[08/24 03:41:40] [DEBUG] TransactionInterceptor: Completing transaction for [usertest.dao.UsersDAO.testInsertAndUpdate] after exception: usertest.exception.BusinessException: Error
[08/24 03:41:40] [DEBUG] RuleBasedTransactionAttribute: Applying rules to determine whether transaction should rollback on usertest.exception.BusinessException: Error
[08/24 03:41:40] [DEBUG] RuleBasedTransactionAttribute: Winning rollback rule is: RollbackRuleAttribute with pattern [Exception]
[08/24 03:41:40] [DEBUG] DataSourceTransactionManager: Triggering beforeCompletion synchronization
[08/24 03:41:40] [DEBUG] DataSourceTransactionManager: Initiating transaction rollback
[08/24 03:41:40] [DEBUG] DataSourceTransactionManager: Rolling back JDBC transaction on Connection [org.apache.commons.dbcp.PoolableConnection@1db05b2]
[08/24 03:41:40] [DEBUG] DataSourceTransactionManager: Triggering afterCompletion synchronization
[08/24 03:41:40] [DEBUG] TransactionSynchronizationManager: Clearing transaction synchronization
