spring事务同步管理器

一、TransactionSynchronization

spring事务各个声命周期的扩展对象

public interface TransactionSynchronization extends Flushable {

	/** 事务提交状态 */
	int STATUS_COMMITTED = 0;

	/** 事务回滚状态 */
	int STATUS_ROLLED_BACK = 1;

	/**系统异常状态 */
	int STATUS_UNKNOWN = 2;

	void suspend();

	void resume();

	void flush();

	// 事务提交之前
	void beforeCommit(boolean readOnly);

	// 事务成功或者事务回滚之前
	void beforeCompletion();

	// 事务成功提交之后
	void afterCommit();

	// 操作完成之后(包含事务成功或者事务回滚)
	void afterCompletion(int status);

}

二、TransactionSynchronizationManager

public abstract class TransactionSynchronizationManager {
	//保存连接资源，因为一个方法里面可能包含多个事务，所以就用 Map 来保存资源.
	private static final ThreadLocal<Map<Object, Object>> resources =
			new NamedThreadLocal<>("Transactional resources");

	//事务的扩展对象
	private static final ThreadLocal<Set<TransactionSynchronization>> synchronizations =
			new NamedThreadLocal<>("Transaction synchronizations");
	//当前事务名称
	private static final ThreadLocal<String> currentTransactionName =
			new NamedThreadLocal<>("Current transaction name");
    //当前事务是否只读
	private static final ThreadLocal<Boolean> currentTransactionReadOnly =
			new NamedThreadLocal<>("Current transaction read-only status");
	//当前事务的隔离级别
	private static final ThreadLocal<Integer> currentTransactionIsolationLevel =
			new NamedThreadLocal<>("Current transaction isolation level");
	//当前事务是否还是 Active 状态
	private static final ThreadLocal<Boolean> actualTransactionActive =
			new NamedThreadLocal<>("Actual transaction active");
	}