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：

 <bean id=“baseTxProxy” lazy-init=“true”class=“org.springframework.transaction.interceptor.TransactionProxyFactoryBean” scope=“singleton” abstract=“true”>
   <property name=“transactionManager”>
    <ref local=“transactionManager” />
   </property>
   <property name=“transactionAttributes”>
    <props>
     <prop key=“register*”>PROPAGATION_REQUIRED</prop>
     <prop key=“trade*”>PROPAGATION_REQUIRED</prop>
     <prop key=“cancel*”>PROPAGATION_REQUIRED</prop>
     <prop key="save*">PROPAGATION_REQUIRED,-ApplicationException,+BusinessException</prop>
     <prop key=“exe*”>PROPAGATION_REQUIRED</prop>
     <prop key=“add*”>PROPAGATION_REQUIRED</prop>
     <prop key=“persist*”>PROPAGATION_REQUIRED</prop>
     <prop key=“remove*”>PROPAGATION_REQUIRED</prop>
     <prop key=“del*”>PROPAGATION_REQUIRED</prop>
     <prop key=“update*”>PROPAGATION_REQUIRED</prop>
     <prop key=“gen*”>PROPAGATION_REQUIRED</prop>
     <prop key=“finish*”>PROPAGATION_REQUIRED</prop>
     <prop key=“get*”>PROPAGATION_REQUIRED,readOnly</prop>
     <prop key=“find*”>PROPAGATION_REQUIRED,readOnly</prop>
     <prop key=“query*”>PROPAGATION_REQUIRED,readOnly</prop>
     <prop key=“select*”>PROPAGATION_REQUIRED,readOnly</prop>
     <prop key=“is*”>PROPAGATION_REQUIRED,readOnly</prop>
    </props>
   </property>
 </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)

 public boolean rollbackOn(Throwable ex) {
         if (logger.isTraceEnabled()) {
             logger.trace("Applying rules to determine whether transaction should rollback on " + ex);
         }

         RollbackRuleAttribute winner = null;
         int deepest = Integer.MAX_VALUE;

         //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
         if (this.rollbackRules != null) {
             for (RollbackRuleAttribute rule : this.rollbackRules) {
                 //使用抛出exception的className(全路径className)进行indexOf match
                 //如果没有match上会继续搜索superClass name进行match，到Throwable class为止
                 int depth = rule.getDepth(ex);
                 if (depth >= 0 && depth < deepest) {
                     deepest = depth;
                     winner = rule;
                 }
             }
         }

         if (logger.isTraceEnabled()) {
             logger.trace("Winning rollback rule is: " + winner);
         }

         // User superclass behavior (rollback on unchecked) if no rule matches.
         if (winner == null) {
             logger.trace("No relevant rollback rule found: applying default rules");
             //如果没有match上，调用此方法继续match，判断instance of RuntimeException or Error
             return super.rollbackOn(ex);
         }

         return !(winner instanceof NoRollbackRuleAttribute);
     }

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。

   public int getDepth(Throwable ex) {
     return getDepth(ex.getClass(), 0);
 }  

 　private int getDepth(Class exceptionClass, int depth) {
     if (exceptionClass.getName().indexOf(this.exceptionName) != -1) {
         // Found it!
         return depth;
     }
     // If we've gone as far as we can go and haven't found it...
     if (exceptionClass.equals(Throwable.class)) {
         return -1;
     }
     return getDepth(exceptionClass.getSuperclass(), depth + 1);
 }  

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。

 public boolean rollbackOn(Throwable ex) {
         return (ex instanceof RuntimeException || ex instanceof Error);
     } 

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