之前的Domain Service Owner Transaction Design Pattern已经提到了Spring的事务机制和Spring事务设计， Spring的transaction事务管理应该是Spring应用广泛的最大原因，但是我们中国的Java开发者好像并不知道Spring的事务到底是怎么回事。所以，我转载一段Spring官方参考文档说明Spring的事务回滚机制。

Spring框架的事务基础架构代码将默认地 只 在抛出运行时和unchecked exceptions时才标识事务回滚。 也就是说，当抛出一个 RuntimeException 或其子类例的实例时。（Errors 也一样 - 默认地 - 标识事务回滚。）从事务方法中抛出的Checked exceptions将 不 被标识进行事务回滚。

The previous section outlined the basics of how to specify the transactional settings for the classes, typically service layer classes, in your application in a declarative fashion. This section describes how you can control the rollback of transactions in a simple declarative fashion.

The recommended way to indicate to the Spring Framework's transaction infrastructure that a transaction's work is to be rolled back is to throw an Exception from code that is currently executing in the context of a transaction. The Spring Framework's transaction infrastructure code will catch any unhandled Exception as it bubbles up the call stack, and will mark the transaction for rollback.

However, please note that the Spring Framework's transaction infrastructure code will, by default, only mark a transaction for rollback in the case of runtime, unchecked exceptions; that is, when the thrown exception is an instance or subclass of RuntimeException. (Errors will also - by default - result in a rollback.) Checked exceptions that are thrown from a transactional method will not result in the transaction being rolled back.

Exactly which Exception types mark a transaction for rollback can be configured. Find below a snippet of XML configuration that demonstrates how one would configure rollback for a checked, application-specific Exception type.

<tx:advice id="txAdvice" transaction-manager="txManager">
  <tx:attributes>
	 <tx:method name="get*" read-only="false" rollback-for="NoProductInStockException"/>
	 <tx:method name="*"/>
  </tx:attributes>
</tx:advice>

The second way to indicate to the transaction infrastructure that a rollback is required is to do so programmatically. Although very simple, this way is quite invasive, and tightly couples your code to the Spring Framework's transaction infrastructure. Find below a snippet of code that does programmatic rollback of a Spring Framework-managed transaction:

public void resolvePosition() {
    try {
        // some business logic...
    } catch (NoProductInStockException ex) {
        // trigger rollback programmatically
        TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
    }
}

You are strongly encouraged to use the declarative approach to rollback if at all possible. Programmatic rollback is available should you need it, but its usage flies in the face of achieving a clean POJO-based application model.

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IT瘾于2007年6月20日 下午08时07分51秒发布 #