begintransaction事务的作用_三问Spring事务：解决什么问题？如何解决？存在什么问题？...

// 开启数据库连接
Connection con &＃61; openConnection();
try {// 关闭自动提交con.setAutoCommit(false);// 业务处理// ... // 提交事务con.commit();
} catch (SQLException | MyException e) {// 捕获异常&＃xff0c;回滚事务try {con.rollback();} catch (SQLException ex) {ex.printStackTrace();}
} finally {// 关闭连接try {con.setAutoCommit(true);con.close();} catch (SQLException e) {e.printStackTrace();}
}

public interface PlatformTransactionManager extends TransactionManager {// 获取事务&＃xff08;新的事务或者已经存在的事务&＃xff09;TransactionStatus getTransaction(&＃64;Nullable TransactionDefinition definition)throws TransactionException; // 提交事务void commit(TransactionStatus status) throws TransactionException;// 回滚事务void rollback(TransactionStatus status) throws TransactionException;
}

public final void commit(TransactionStatus status) throws TransactionException {// 1.检查事务是否已完成if (status.isCompleted()) {throw new IllegalTransactionStateException("Transaction is already completed - do not call commit or rollback more than once per transaction");}// 2.检查事务是否需要回滚&＃xff08;局部事务回滚&＃xff09;DefaultTransactionStatus defStatus &＃61; (DefaultTransactionStatus) status;if (defStatus.isLocalRollbackOnly()) {if (defStatus.isDebug()) {logger.debug("Transactional code has requested rollback");}processRollback(defStatus, false);return;}// 3.检查事务是否需要回滚&＃xff08;全局事务回滚&＃xff09;if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {if (defStatus.isDebug()) {logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");}processRollback(defStatus, true);return;}// 4.提交事务processCommit(defStatus);
}

protected abstract void doCommit(DefaultTransactionStatus status) throws TransactionException;

protected void doCommit(DefaultTransactionStatus status) {// 获取status中的事务对象 DataSourceTransactionObject txObject &＃61; (DataSourceTransactionObject) status.getTransaction();// 通过事务对象获得数据库连接对象Connection con &＃61; txObject.getConnectionHolder().getConnection();if (status.isDebug()) {logger.debug("Committing JDBC transaction on Connection [" &＃43; con &＃43; "]");}try {// 执行commitcon.commit();}catch (SQLException ex) {throw new TransactionSystemException("Could not commit JDBC transaction", ex);}
}

// 获得事务管理器
PlatformTransactionManager txManager &＃61; getPlatformTransactionManager();
DefaultTransactionDefinition def &＃61; new DefaultTransactionDefinition();
// 指定事务元信息
def.setName("SomeTxName");
def.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRED);
// 获得事务
TransactionStatus status &＃61; txManager.getTransaction(def);
try {// 业务处理
}
catch (MyException ex) {// 捕获异常&＃xff0c;回滚事务txManager.rollback(status);throw ex;
}
// 提交事务
txManager.commit(status);

protected void doCommit(DefaultTransactionStatus status) {DataSourceTransactionObject txObject &＃61; (DataSourceTransactionObject) status.getTransaction();Connection con &＃61; txObject.getConnectionHolder().getConnection();if (status.isDebug()) {logger.debug("Committing JDBC transaction on Connection [" &＃43; con &＃43; "]");}try {con.commit();}catch (SQLException ex) {// 异常转换throw new TransactionSystemException("Could not commit JDBC transaction", ex);}
}

protected Object invokeWithinTransaction(Method method, Class targetClass, final InvocationCallback invocation)throws Throwable {// 查询目标方法事务属性、确定事务管理器、构造连接点标识&＃xff08;用于确认事务名称&＃xff09;final TransactionAttribute txAttr &＃61; getTransactionAttributeSource().getTransactionAttribute(method, targetClass);final PlatformTransactionManager tm &＃61; determineTransactionManager(txAttr);final String joinpointIdentification &＃61; methodIdentification(method, targetClass, txAttr);if (txAttr &＃61;&＃61; null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {// 创建事务TransactionInfo txInfo &＃61; createTransactionIfNecessary(tm, txAttr, joinpointIdentification);Object retVal &＃61; null;try {// 通过回调执行目标方法retVal &＃61; invocation.proceedWithInvocation();}catch (Throwable ex) {// 目标方法执行抛出异常&＃xff0c;根据异常类型执行事务提交或者回滚操作completeTransactionAfterThrowing(txInfo, ex);throw ex;}finally {// 清理当前线程事务信息cleanupTransactionInfo(txInfo);}// 目标方法执行成功&＃xff0c;提交事务commitTransactionAfterReturning(txInfo);return retVal;} else {// 带回调的事务执行处理&＃xff0c;一般用于编程式事务// ...}
}

public void saveAB(A a, B b)
{saveA(a);saveB(b);
}&＃64;Transactional
public void saveA(A a)
{dao.saveA(a);
}&＃64;Transactional
public void saveB(B b)
{dao.saveB(b);
}

public void saveAB(A a, B b)
{Test self &＃61; (Test) applicationContext.getBean("Test");self.saveA(a);self.saveB(b);
}

public void saveAB(A a, B b)
{Test self &＃61; (Test)AopContext.currentProxy();self.saveA(a);self.saveB(b);
}

&＃64;Component
public class Test {&＃64;AutowiredTest self;public void saveAB(A a, B b){self.saveA(a);self.saveB(b);}// ...
}

public void saveAB(A a, B b)
{txOperate.saveA(a);txOperate.saveB(b);
}

protected void completeTransactionAfterThrowing(&＃64;Nullable TransactionInfo txInfo, Throwable ex) {if (txInfo !&＃61; null && txInfo.getTransactionStatus() !&＃61; null) {if (logger.isTraceEnabled()) {logger.trace("Completing transaction for [" &＃43; txInfo.getJoinpointIdentification() &＃43;"] after exception: " &＃43; ex);}if (txInfo.transactionAttribute !&＃61; null && txInfo.transactionAttribute.rollbackOn(ex)) {try {// 异常类型为回滚异常&＃xff0c;执行事务回滚txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());}catch (TransactionSystemException ex2) {logger.error("Application exception overridden by rollback exception", ex);ex2.initApplicationException(ex);throw ex2;}catch (RuntimeException | Error ex2) {logger.error("Application exception overridden by rollback exception", ex);throw ex2;}}else {try {// 异常类型为非回滚异常&＃xff0c;仍然执行事务提交txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());}catch (TransactionSystemException ex2) {logger.error("Application exception overridden by commit exception", ex);ex2.initApplicationException(ex);throw ex2;}catch (RuntimeException | Error ex2) {logger.error("Application exception overridden by commit exception", ex);throw ex2;}}}
}

&＃64;Transactional
public void insert(List users) {try {JdbcTemplate jdbcTemplate &＃61; new JdbcTemplate(dataSource);for (User user : users) {String insertUserSql &＃61; "insert into User (id, name) values (?,?)";jdbcTemplate.update(insertUserSql, new Object[] { user.getId(),user.getName() });}} catch (Exception e) {e.printStackTrace();}
}