spring JDBC事务使用经验

       最近在使用spring的JDBC事务时出现了一个问题：在多线程环境中，主线程获取一个

DataSourceTransactionManager，开启事务，同时在子线程中也使用同一个事务管理器开启事务，但是当子线程中的事务发生回滚后，主线程的事务继续执行，没有同步回滚。因此我怀疑spring JDBC事务不支持跨线程，于是乎翻阅了spring中关于事务的代码，发现果然如此，其关键在于TransactionSynchronizationManager中，代码如下：

package org.springframework.transaction.support;
/**
* Central helper that manages resources and transaction synchronizations per thread.
* To be used by resource management code but not by typical application code.
*
* <p>Supports one resource per key without overwriting, that is, a resource needs
* to be removed before a new one can be set for the same key.
* Supports a list of transaction synchronizations if synchronization is active.
*
* <p>Resource management code should check for thread-bound resources, e.g. JDBC
* Connections or Hibernate Sessions, via <code>getResource</code>. Such code is
* normally not supposed to bind resources to threads, as this is the responsibility
* of transaction managers. A further option is to lazily bind on first use if
* transaction synchronization is active, for performing transactions that span
* an arbitrary number of resources.
*
* <p>Transaction synchronization must be activated and deactivated by a transaction
* manager via {@link #initSynchronization()} and {@link #clearSynchronization()}.
* This is automatically supported by {@link AbstractPlatformTransactionManager},
* and thus by all standard Spring transaction managers, such as
* {@link org.springframework.transaction.jta.JtaTransactionManager} and
* {@link org.springframework.jdbc.datasource.DataSourceTransactionManager}.
*
* <p>Resource management code should only register synchronizations when this
* manager is active, which can be checked via {@link #isSynchronizationActive};
* it should perform immediate resource cleanup else. If transaction synchronization
* isn't active, there is either no current transaction, or the transaction manager
* doesn't support transaction synchronization.
*
* <p>Synchronization is for example used to always return the same resources
* within a JTA transaction, e.g. a JDBC Connection or a Hibernate Session for
* any given DataSource or SessionFactory, respectively.
*
* @author Juergen Hoeller
* @since 02.06.2003
* @see #isSynchronizationActive
* @see #registerSynchronization
* @see TransactionSynchronization
* @see AbstractPlatformTransactionManager#setTransactionSynchronization
* @see org.springframework.transaction.jta.JtaTransactionManager
* @see org.springframework.jdbc.datasource.DataSourceTransactionManager
* @see org.springframework.jdbc.datasource.DataSourceUtils#getConnection
*/
public abstract class TransactionSynchronizationManager {
private static final Log logger = LogFactory.getLog(TransactionSynchronizationManager.class);
//所有关于事务的资源变量都定义成了线程变量，所以jdbc事务不支持跨线程
//resources资源用来存储connection，key是DataSource（把连接与当前线程绑定，保证一个事务使用一个连接）。spring团队把带有状态的connection与当前线程绑定，设计的非常巧妙！！
private static final ThreadLocal<Map<Object, Object>> resources =
new NamedThreadLocal<Map<Object, Object>>("Transactional resources");

private static final ThreadLocal<Set<TransactionSynchronization>> synchronizations =
new NamedThreadLocal<Set<TransactionSynchronization>>("Transaction synchronizations");

private static final ThreadLocal<String> currentTransactionName =
new NamedThreadLocal<String>("Current transaction name");

private static final ThreadLocal<Boolean> currentTransactionReadOnly =
new NamedThreadLocal<Boolean>("Current transaction read-only status");

private static final ThreadLocal<Integer> currentTransactionIsolationLevel =
new NamedThreadLocal<Integer>("Current transaction isolation level");

private static final ThreadLocal<Boolean> actualTransactionActive =
new NamedThreadLocal<Boolean>("Actual transaction active");

//-------------------------------------------------------------------------
// Management of transaction-associated resource handles
//-------------------------------------------------------------------------

.......

}

         特别记录下来，防止以后忘记！！！！！遇到同样问题的童鞋也可以参考一下，共同进步！！