spring 註解試事物源碼解析

spring 註解試事物源碼解析

• 基於xml註解式事務入口

    public class TxNamespaceHandler extends NamespaceHandlerSupport {

    static final String TRANSACTION_MANAGER_ATTRIBUTE = "transaction-manager";

    static final String DEFAULT_TRANSACTION_MANAGER_BEAN_NAME = "transactionManager";


    static String getTransactionManagerName(Element element) {
        return (element.hasAttribute(TRANSACTION_MANAGER_ATTRIBUTE) ?
                element.getAttribute(TRANSACTION_MANAGER_ATTRIBUTE) : DEFAULT_TRANSACTION_MANAGER_BEAN_NAME);
    }


    @Override
    public void init() {
        registerBeanDefinitionParser("advice", new TxAdviceBeanDefinitionParser());
        registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
        registerBeanDefinitionParser("jta-transaction-manager", new JtaTransactionManagerBeanDefinitionParser());
    }

}

基於註解的事務啓動入口

@Configuration
public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration {
    // 事務增強器
    @Bean(name = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME)
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor() {
        BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor();
        advisor.setTransactionAttributeSource(transactionAttributeSource());
        advisor.setAdvice(transactionInterceptor());
        advisor.setOrder(this.enableTx.<Integer>getNumber("order"));
        return advisor;
    }
    // 事務的屬性資源
    @Bean
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public TransactionAttributeSource transactionAttributeSource() {
        return new AnnotationTransactionAttributeSource();
    }
    // 事務的攔截器
    @Bean
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public TransactionInterceptor transactionInterceptor() {
        TransactionInterceptor interceptor = new TransactionInterceptor();
        interceptor.setTransactionAttributeSource(transactionAttributeSource());
        if (this.txManager != null) {
            interceptor.setTransactionManager(this.txManager);
        }
        return interceptor;
    }

}

事務bean的增強器

public class BeanFactoryTransactionAttributeSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {

    private TransactionAttributeSource transactionAttributeSource;

    private final TransactionAttributeSourcePointcut pointcut = new TransactionAttributeSourcePointcut() {
        @Override
        protected TransactionAttributeSource getTransactionAttributeSource() {
            return transactionAttributeSource;
        }
    };


    // 設置事務的屬性資源
    public void setTransactionAttributeSource(TransactionAttributeSource transactionAttributeSource) {
        this.transactionAttributeSource = transactionAttributeSource;
    }

    /**
     * Set the {@link ClassFilter} to use for this pointcut.
     * Default is {@link ClassFilter#TRUE}.
     */
    public void setClassFilter(ClassFilter classFilter) {
        this.pointcut.setClassFilter(classFilter);
    }

    @Override
    public Pointcut getPointcut() {
        return this.pointcut;
    }

}

事務攔截器

TransactionInterceptor.java

@Override
    public Object invoke(final MethodInvocation invocation) throws Throwable {
        // Work out the target class: may be {@code null}.
        // The TransactionAttributeSource should be passed the target class
        // as well as the method, which may be from an interface.
        Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);

        // Adapt to TransactionAspectSupport's invokeWithinTransaction...
        return invokeWithinTransaction(invocation.getMethod(), targetClass, new InvocationCallback() {
            @Override
            public Object proceedWithInvocation() throws Throwable {
                return invocation.proceed();
            }
        });
    }

TransactionAspectSupport.java

protected Object invokeWithinTransaction(Method method, Class<?> targetClass, final InvocationCallback invocation)
            throws Throwable {

        // 獲取事務對應的屬性
        final TransactionAttribute txAttr = getTransactionAttributeSource().getTransactionAttribute(method, targetClass);
        // 獲取事務管理器
        final PlatformTransactionManager tm = determineTransactionManager(txAttr);
        final String joinpointIdentification = methodIdentification(method, targetClass);

        if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
            // 創建TransactionInfo
            TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
            Object retVal = null;
            try {
                // 執行被增強的方法
                retVal = invocation.proceedWithInvocation();
            }
            catch (Throwable ex) {
                // 異常回滾
                completeTransactionAfterThrowing(txInfo, ex);
                throw ex;
            }
            finally {
                // 清除事務信息
                cleanupTransactionInfo(txInfo);
            }
            // 提交事務
            commitTransactionAfterReturning(txInfo);
            return retVal;
        }

        else {
            // 編程式事務處理
            try {
                Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr,
                        new TransactionCallback<Object>() {
                            @Override
                            public Object doInTransaction(TransactionStatus status) {
                                TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
                                try {
                                    return invocation.proceedWithInvocation();
                                }
                                catch (Throwable ex) {
                                    if (txAttr.rollbackOn(ex)) {
                                        // A RuntimeException: will lead to a rollback.
                                        if (ex instanceof RuntimeException) {
                                            throw (RuntimeException) ex;
                                        }
                                        else {
                                            throw new ThrowableHolderException(ex);
                                        }
                                    }
                                    else {
                                        // A normal return value: will lead to a commit.
                                        return new ThrowableHolder(ex);
                                    }
                                }
                                finally {
                                    cleanupTransactionInfo(txInfo);
                                }
                            }
                        });

                // Check result: It might indicate a Throwable to rethrow.
                if (result instanceof ThrowableHolder) {
                    throw ((ThrowableHolder) result).getThrowable();
                }
                else {
                    return result;
                }
            }
            catch (ThrowableHolderException ex) {
                throw ex.getCause();
            }
        }
    }

獲取對應的事物屬性

protected TransactionInfo createTransactionIfNecessary(
            PlatformTransactionManager tm, TransactionAttribute txAttr, final String joinpointIdentification) {

        // 沒有名稱 就用 joinpointIdentification 當名稱
        if (txAttr != null && txAttr.getName() == null) {
            txAttr = new DelegatingTransactionAttribute(txAttr) {
                @Override
                public String getName() {
                    return joinpointIdentification;
                }
            };
        }

        TransactionStatus status = null;
        if (txAttr != null) {
            if (tm != null) {
                // 獲取一個事務狀態
                status = tm.getTransaction(txAttr);
            }
            else {
                if (logger.isDebugEnabled()) {
                    logger.debug("Skipping transactional joinpoint [" + joinpointIdentification +
                            "] because no transaction manager has been configured");
                }
            }
        }
        return prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
    }

獲取一個事務狀態

AbstractPlatformTransactionManager.java

@Override
    public final TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException {
        Object transaction = doGetTransaction();

        // Cache debug flag to avoid repeated checks.
        boolean debugEnabled = logger.isDebugEnabled();

        if (definition == null) {
            // Use defaults if no transaction definition given.
            definition = new DefaultTransactionDefinition();
        }
        // 判斷當前的線程是否存在事務，判斷依據是當前線程記錄的連接不爲空且連接中（connectionHolder）
        // 中的transcationActive屬性不爲空
        if (isExistingTransaction(transaction)) {
            // 當前線程已經存在事務
            return handleExistingTransaction(definition, transaction, debugEnabled);
        }

        // 事務超時設置驗證
        if (definition.getTimeout() < TransactionDefinition.TIMEOUT_DEFAULT) {
            throw new InvalidTimeoutException("Invalid transaction timeout", definition.getTimeout());
        }

        // 如果當前線程不存在事務，但是PropagationBehavior==TransactionDefinition.PROPAGATION_MANDATORY 則拋出異常
        if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) {
            throw new IllegalTransactionStateException(
                    "No existing transaction found for transaction marked with propagation 'mandatory'");
        }
        else if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRED ||
                definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW ||
                definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
            // 其他三個情況則新建事務
            // 先掛起一個空事務
            SuspendedResourcesHolder suspendedResources = suspend(null);
            if (debugEnabled) {
                logger.debug("Creating new transaction with name [" + definition.getName() + "]: " + definition);
            }
            try {
                boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
                DefaultTransactionStatus status = newTransactionStatus(
                        definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
                // 構造transaction，包括設置connectionHolder、隔離級別、timeout
                // 如果是新連接，綁定到當前線程
                doBegin(transaction, definition);
                // 新同步事務設置，針對當前線程設置
                prepareSynchronization(status, definition);
                return status;
            }
            catch (RuntimeException ex) {
                resume(null, suspendedResources);
                throw ex;
            }
            catch (Error err) {
                resume(null, suspendedResources);
                throw err;
            }
        }
        else {
            // Create "empty" transaction: no actual transaction, but potentially synchronization.
            if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT && logger.isWarnEnabled()) {
                logger.warn("Custom isolation level specified but no actual transaction initiated; " +
                        "isolation level will effectively be ignored: " + definition);
            }
            boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
            return prepareTransactionStatus(definition, null, true, newSynchronization, debugEnabled, null);
        }
    }

獲取一個事務

DataSourceTransactionManager.java

@Override
    protected Object doGetTransaction() {
        DataSourceTransactionObject txObject = new DataSourceTransactionObject();
        // 設置是否允許保存點
        txObject.setSavepointAllowed(isNestedTransactionAllowed());
        // 如果當前線程已經記錄數據庫連接則使用已有的連接
        ConnectionHolder conHolder =
                (ConnectionHolder) TransactionSynchronizationManager.getResource(this.dataSource);
        txObject.setConnectionHolder(conHolder, false);
        return txObject;
    }

處理已存在的事務

/**
     * Create a TransactionStatus for an existing transaction.
     */
    private TransactionStatus handleExistingTransaction(
            TransactionDefinition definition, Object transaction, boolean debugEnabled)
            throws TransactionException {

        if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NEVER) {
            throw new IllegalTransactionStateException(
                    "Existing transaction found for transaction marked with propagation 'never'");
        }

        if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NOT_SUPPORTED) {
            if (debugEnabled) {
                logger.debug("Suspending current transaction");
            }
            
            Object suspendedResources = suspend(transaction);
            boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
            return prepareTransactionStatus(
                    definition, null, false, newSynchronization, debugEnabled, suspendedResources);
        }
        
        if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW) {
            if (debugEnabled) {
                logger.debug("Suspending current transaction, creating new transaction with name [" +
                        definition.getName() + "]");
            }
            // 新事務連接
            SuspendedResourcesHolder suspendedResources = suspend(transaction);
            try {
                boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
                DefaultTransactionStatus status = newTransactionStatus(
                        definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
                doBegin(transaction, definition);
                prepareSynchronization(status, definition);
                return status;
            }
            catch (RuntimeException beginEx) {
                resumeAfterBeginException(transaction, suspendedResources, beginEx);
                throw beginEx;
            }
            catch (Error beginErr) {
                resumeAfterBeginException(transaction, suspendedResources, beginErr);
                throw beginErr;
            }
        }
        // 嵌入式事務的處理
        if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
            if (!isNestedTransactionAllowed()) {
                throw new NestedTransactionNotSupportedException(
                        "Transaction manager does not allow nested transactions by default - " +
                        "specify 'nestedTransactionAllowed' property with value 'true'");
            }
            if (debugEnabled) {
                logger.debug("Creating nested transaction with name [" + definition.getName() + "]");
            }
            if (useSavepointForNestedTransaction()) {
                // 如果沒有可以使用的保存點的方式控制事務回滾，那麼嵌入式事務的建立初始建立保存點
                DefaultTransactionStatus status =
                        prepareTransactionStatus(definition, transaction, false, false, debugEnabled, null);
                status.createAndHoldSavepoint();
                return status;
            }
            else {
                // 有些情況不能使用保存點，如果jat，那麼建立新事務
                boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
                DefaultTransactionStatus status = newTransactionStatus(
                        definition, transaction, true, newSynchronization, debugEnabled, null);
                doBegin(transaction, definition);
                prepareSynchronization(status, definition);
                return status;
            }
        }

        // Assumably PROPAGATION_SUPPORTS or PROPAGATION_REQUIRED.
        if (debugEnabled) {
            logger.debug("Participating in existing transaction");
        }
        if (isValidateExistingTransaction()) {
            if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) {
                Integer currentIsolationLevel = TransactionSynchronizationManager.getCurrentTransactionIsolationLevel();
                if (currentIsolationLevel == null || currentIsolationLevel != definition.getIsolationLevel()) {
                    Constants isoConstants = DefaultTransactionDefinition.constants;
                    throw new IllegalTransactionStateException("Participating transaction with definition [" +
                            definition + "] specifies isolation level which is incompatible with existing transaction: " +
                            (currentIsolationLevel != null ?
                                    isoConstants.toCode(currentIsolationLevel, DefaultTransactionDefinition.PREFIX_ISOLATION) :
                                    "(unknown)"));
                }
            }
            if (!definition.isReadOnly()) {
                if (TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
                    throw new IllegalTransactionStateException("Participating transaction with definition [" +
                            definition + "] is not marked as read-only but existing transaction is");
                }
            }
        }
        boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
        return prepareTransactionStatus(definition, transaction, false, newSynchronization, debugEnabled, null);
    }

構造事務，並且配置隔離級別和timeout

@Override
    protected void doBegin(Object transaction, TransactionDefinition definition) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
        Connection con = null;

        try {
            if (txObject.getConnectionHolder() == null ||
                    txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
                Connection newCon = this.dataSource.getConnection();
                if (logger.isDebugEnabled()) {
                    logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
                }
                txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
            }

            txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
            con = txObject.getConnectionHolder().getConnection();
            // 設置隔離級別
            Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
            txObject.setPreviousIsolationLevel(previousIsolationLevel);

            // 更改自動提交配置，有spring控制提交
            if (con.getAutoCommit()) {
                txObject.setMustRestoreAutoCommit(true);
                if (logger.isDebugEnabled()) {
                    logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
                }
                con.setAutoCommit(false);
            }
            // 設置當前線程是否存在事務的依據
            txObject.getConnectionHolder().setTransactionActive(true);
            
            //設置timeout
            int timeout = determineTimeout(definition);
            if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
                txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
            }

            // 將當前獲取到的連接綁定到當前線程
            if (txObject.isNewConnectionHolder()) {
                TransactionSynchronizationManager.bindResource(getDataSource(), txObject.getConnectionHolder());
            }
        }

        catch (Throwable ex) {
            if (txObject.isNewConnectionHolder()) {
                DataSourceUtils.releaseConnection(con, this.dataSource);
                txObject.setConnectionHolder(null, false);
            }
            throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
        }
    }

新同步事務的設置

protected void prepareSynchronization(DefaultTransactionStatus status, TransactionDefinition definition) {
        if (status.isNewSynchronization()) {
            TransactionSynchronizationManager.setActualTransactionActive(status.hasTransaction());
            TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(
                    definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT ?
                            definition.getIsolationLevel() : null);
            TransactionSynchronizationManager.setCurrentTransactionReadOnly(definition.isReadOnly());
            TransactionSynchronizationManager.setCurrentTransactionName(definition.getName());
            TransactionSynchronizationManager.initSynchronization();
        }
    }

準備事務信息

protected TransactionInfo prepareTransactionInfo(PlatformTransactionManager tm,
            TransactionAttribute txAttr, String joinpointIdentification, TransactionStatus status) {

        TransactionInfo txInfo = new TransactionInfo(tm, txAttr, joinpointIdentification);
        if (txAttr != null) {
            // We need a transaction for this method
            if (logger.isTraceEnabled()) {
                logger.trace("Getting transaction for [" + txInfo.getJoinpointIdentification() + "]");
            }
            // 記錄事務狀態
            txInfo.newTransactionStatus(status);
        }
        else {
            // The TransactionInfo.hasTransaction() method will return
            // false. We created it only to preserve the integrity of
            // the ThreadLocal stack maintained in this class.
            if (logger.isTraceEnabled())
                logger.trace("Don't need to create transaction for [" + joinpointIdentification +
                        "]: This method isn't transactional.");
        }

        // We always bind the TransactionInfo to the thread, even if we didn't create
        // a new transaction here. This guarantees that the TransactionInfo stack
        // will be managed correctly even if no transaction was created by this aspect.
        txInfo.bindToThread();
        return txInfo;
    }

回滾處理

protected void completeTransactionAfterThrowing(TransactionInfo txInfo, Throwable ex) {
    // 當拋出異常時首先判斷當前是否存在事務，    
    if (txInfo != null && txInfo.hasTransaction()) {
            if (logger.isTraceEnabled()) {
                logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
                        "] after exception: " + ex);
            }
            // 這裏判斷是否回滾的依據是拋出的異常是否runtimeException活着error， 默認實現
            if (txInfo.transactionAttribute.rollbackOn(ex)) {
                try {
                    //處理回滾信息
                txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
                }
                catch (TransactionSystemException ex2) {
                    logger.error("Application exception overridden by rollback exception", ex);
                    ex2.initApplicationException(ex);
                    throw ex2;
                }
                catch (RuntimeException ex2) {
                    logger.error("Application exception overridden by rollback exception", ex);
                    throw ex2;
                }
                catch (Error err) {
                    logger.error("Application exception overridden by rollback error", ex);
                    throw err;
                }
            }
            else {
                // 如果不滿足條件則拋出異常也會提交
                try {
                    txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
                }
                catch (TransactionSystemException ex2) {
                    logger.error("Application exception overridden by commit exception", ex);
                    ex2.initApplicationException(ex);
                    throw ex2;
                }
                catch (RuntimeException ex2) {
                    logger.error("Application exception overridden by commit exception", ex);
                    throw ex2;
                }
                catch (Error err) {
                    logger.error("Application exception overridden by commit error", ex);
                    throw err;
                }
            }
        }
    }

DefaultTransactionAttribute.java

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

AbstractPlatformTransactionManager.java

@Override
    public final void rollback(TransactionStatus status) throws TransactionException {
        // 如果事務完成再次回滾會拋出異常
        if (status.isCompleted()) {
            throw new IllegalTransactionStateException(
                    "Transaction is already completed - do not call commit or rollback more than once per transaction");
        }

        DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;
        processRollback(defStatus);
    }

如果有保存點則回到保存點

private void processRollback(DefaultTransactionStatus status) {
        try {
            try {
                triggerBeforeCompletion(status);
                if (status.hasSavepoint()) {
                    if (status.isDebug()) {
                        logger.debug("Rolling back transaction to savepoint");
                    }
                    // 如果有保存點則回到保存點
                    status.rollbackToHeldSavepoint();
                }
                else if (status.isNewTransaction()) {
                    if (status.isDebug()) {
                        logger.debug("Initiating transaction rollback");
                    }
                    // 如果是新事務則回滾
                    doRollback(status);
                }
                else if (status.hasTransaction()) {
                    // 有事務標識又不屬於上面兩種情況的，多屬於jta，只能做標記，在提交的時候回退
                    if (status.isLocalRollbackOnly() || isGlobalRollbackOnParticipationFailure()) {
                        if (status.isDebug()) {
                            logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
                        }
                        doSetRollbackOnly(status);
                    }
                    else {
                        if (status.isDebug()) {
                            logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
                        }
                    }
                }
                else {
                    logger.debug("Should roll back transaction but cannot - no transaction available");
                }
            }
            catch (RuntimeException ex) {
                triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
                throw ex;
            }
            catch (Error err) {
                triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
                throw err;
            }
            triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
        }
        finally {
            cleanupAfterCompletion(status);
        }
    }

AbstractTransactionStatus.java

public void rollbackToHeldSavepoint() throws TransactionException {
        if (!hasSavepoint()) {
            throw new TransactionUsageException(
                    "Cannot roll back to savepoint - no savepoint associated with current transaction");
        }
        // 回滾到保存點
        getSavepointManager().rollbackToSavepoint(getSavepoint());
        // 釋放掉這個保存點
        getSavepointManager().releaseSavepoint(getSavepoint());
        setSavepoint(null);
    }

JdbcTransactionObjectSupport.java

@Override
    public void rollbackToSavepoint(Object savepoint) throws TransactionException {
        ConnectionHolder conHolder = getConnectionHolderForSavepoint();
        try {
            conHolder.getConnection().rollback((Savepoint) savepoint);
        }
        catch (Throwable ex) {
            throw new TransactionSystemException("Could not roll back to JDBC savepoint", ex);
        }
    }

    /**
     * This implementation releases the given JDBC 3.0 Savepoint.
     * @see java.sql.Connection#releaseSavepoint
     */
    @Override
    public void releaseSavepoint(Object savepoint) throws TransactionException {
        ConnectionHolder conHolder = getConnectionHolderForSavepoint();
        try {
            conHolder.getConnection().releaseSavepoint((Savepoint) savepoint);
        }
        catch (Throwable ex) {
            logger.debug("Could not explicitly release JDBC savepoint", ex);
        }
    }

新事務則直接回退

@Override
    protected void doRollback(DefaultTransactionStatus status) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
        Connection con = txObject.getConnectionHolder().getConnection();
        if (status.isDebug()) {
            logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
        }
        try {
            con.rollback();
        }
        catch (SQLException ex) {
            throw new TransactionSystemException("Could not roll back JDBC transaction", ex);
        }
    }

回退後信息清理

private void cleanupAfterCompletion(DefaultTransactionStatus status) {
        // 設置事務完成狀態
        status.setCompleted();
        if (status.isNewSynchronization()) {
            TransactionSynchronizationManager.clear();
        }
        if (status.isNewTransaction()) {
            doCleanupAfterCompletion(status.getTransaction());
        }
        if (status.getSuspendedResources() != null) {
            if (status.isDebug()) {
                logger.debug("Resuming suspended transaction after completion of inner transaction");
            }
            // 結束之前掛起的事務
            resume(status.getTransaction(), (SuspendedResourcesHolder) status.getSuspendedResources());
        }
    }

TransactionSynchronizationManager.java

public static void clear() {
        clearSynchronization();
        setCurrentTransactionName(null);
        setCurrentTransactionReadOnly(false);
        setCurrentTransactionIsolationLevel(null);
        setActualTransactionActive(false);
    }

@Override
    protected void doCleanupAfterCompletion(Object transaction) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;

        // 解綁數據源
        if (txObject.isNewConnectionHolder()) {
            TransactionSynchronizationManager.unbindResource(this.dataSource);
        }

        // 釋放數據庫連接
        Connection con = txObject.getConnectionHolder().getConnection();
        try {
            // 恢復數據庫的自動提交屬性
            if (txObject.isMustRestoreAutoCommit()) {
                con.setAutoCommit(true);
            }
            // 重製數據庫連接
            DataSourceUtils.resetConnectionAfterTransaction(con, txObject.getPreviousIsolationLevel());
        }
        catch (Throwable ex) {
            logger.debug("Could not reset JDBC Connection after transaction", ex);
        }

        if (txObject.isNewConnectionHolder()) {
            if (logger.isDebugEnabled()) {
                logger.debug("Releasing JDBC Connection [" + con + "] after transaction");
            }
            //如果當前事務時獨立的新創建的事務則在完成事務時釋放數據庫連接
            DataSourceUtils.releaseConnection(con, this.dataSource);
        }
        
        txObject.getConnectionHolder().clear();
    }

protected final void resume(Object transaction, SuspendedResourcesHolder resourcesHolder)
            throws TransactionException {
        // 如果在事務執行前有掛起，那麼在這裏恢復這個事務
        if (resourcesHolder != null) {
            Object suspendedResources = resourcesHolder.suspendedResources;
            if (suspendedResources != null) {
                doResume(transaction, suspendedResources);
            }
            List<TransactionSynchronization> suspendedSynchronizations = resourcesHolder.suspendedSynchronizations;
            if (suspendedSynchronizations != null) {
                TransactionSynchronizationManager.setActualTransactionActive(resourcesHolder.wasActive);
                TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(resourcesHolder.isolationLevel);
                TransactionSynchronizationManager.setCurrentTransactionReadOnly(resourcesHolder.readOnly);
                TransactionSynchronizationManager.setCurrentTransactionName(resourcesHolder.name);
                doResumeSynchronization(suspendedSynchronizations);
            }
        }
    }

@Override
    protected void doResume(Object transaction, Object suspendedResources) {
        ConnectionHolder conHolder = (ConnectionHolder) suspendedResources;
        TransactionSynchronizationManager.bindResource(this.dataSource, conHolder);
    }

事務的提交

protected void commitTransactionAfterReturning(TransactionInfo txInfo) {
        if (txInfo != null && txInfo.hasTransaction()) {
            if (logger.isTraceEnabled()) {
                logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() + "]");
            }
            txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
        }
    }

@Override
    public final void commit(TransactionStatus status) throws TransactionException {
        if (status.isCompleted()) {
            throw new IllegalTransactionStateException(
                    "Transaction is already completed - do not call commit or rollback more than once per transaction");
        }
        
        DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;
        // 如果有標記爲回滾的狀態則回滾
        if (defStatus.isLocalRollbackOnly()) {
            if (defStatus.isDebug()) {
                logger.debug("Transactional code has requested rollback");
            }
            processRollback(defStatus);
            return;
        }
        if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
            if (defStatus.isDebug()) {
                logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
            }
            processRollback(defStatus);
            // Throw UnexpectedRollbackException only at outermost transaction boundary
            // or if explicitly asked to.
            if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {
                throw new UnexpectedRollbackException(
                        "Transaction rolled back because it has been marked as rollback-only");
            }
            return;
        }

        processCommit(defStatus);
    }

private void processCommit(DefaultTransactionStatus status) throws TransactionException {
        try {
            boolean beforeCompletionInvoked = false;
            try {
                prepareForCommit(status);
                triggerBeforeCommit(status);
                triggerBeforeCompletion(status);
                beforeCompletionInvoked = true;
                boolean globalRollbackOnly = false;
                if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {
                    globalRollbackOnly = status.isGlobalRollbackOnly();
                }
                if (status.hasSavepoint()) {
                    if (status.isDebug()) {
                        logger.debug("Releasing transaction savepoint");
                    }
                    // 如果存在保存點則清除保存點
                    status.releaseHeldSavepoint();
                }
                else if (status.isNewTransaction()) {
                    if (status.isDebug()) {
                        logger.debug("Initiating transaction commit");
                    }
                    // 如果是新事務則提交
                    doCommit(status);
                }
                // Throw UnexpectedRollbackException if we have a global rollback-only
                // marker but still didn't get a corresponding exception from commit.
                if (globalRollbackOnly) {
                    throw new UnexpectedRollbackException(
                            "Transaction silently rolled back because it has been marked as rollback-only");
                }
            }
            catch (UnexpectedRollbackException ex) {
                // can only be caused by doCommit
                triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
                throw ex;
            }
            catch (TransactionException ex) {
                // can only be caused by doCommit
                if (isRollbackOnCommitFailure()) {
                    doRollbackOnCommitException(status, ex);
                }
                else {
                    triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
                }
                throw ex;
            }
            catch (RuntimeException ex) {
                if (!beforeCompletionInvoked) {
                    triggerBeforeCompletion(status);
                }
                doRollbackOnCommitException(status, ex);
                throw ex;
            }
            catch (Error err) {
                if (!beforeCompletionInvoked) {
                    triggerBeforeCompletion(status);
                }
                doRollbackOnCommitException(status, err);
                throw err;
            }

            // Trigger afterCommit callbacks, with an exception thrown there
            // propagated to callers but the transaction still considered as committed.
            try {
                triggerAfterCommit(status);
            }
            finally {
                triggerAfterCompletion(status, TransactionSynchronization.STATUS_COMMITTED);
            }

        }
        finally {
            cleanupAfterCompletion(status);
        }
    }

protected void doCommit(DefaultTransactionStatus status) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
        Connection con = txObject.getConnectionHolder().getConnection();
        if (status.isDebug()) {
            logger.debug("Committing JDBC transaction on Connection [" + con + "]");
        }
        try {
            // 終於可以愉快的提交這個事務了
            con.commit();
        }
        catch (SQLException ex) {
            throw new TransactionSystemException("Could not commit JDBC transaction", ex);
        }
    }