今天这篇，就给大家分析一下Seata的源码是如何一步一步实现的。读源码的时候我们需要俯瞰起全貌，不要去扣一个一个的细节，这样我们学习起来会快捷而且有效率，我们学习源码需要掌握的是整体思路和核心点。

首先Seata客户端启动一般分为以下几个流程：

(资料图)

在这篇源码的讲解中，我们主要以AT模式为主导，官网也是主推AT模式，我们在上篇的文章中也讲解过，感兴趣的小伙伴可以去看一看​​分布式事务(Seata) 四大模式详解​​，在官网中也提供了对应的流程地址：https://seata.io/zh-cn/docs/dev/mode/at-mode.html ，在这里我们只是做一些简单的介绍，AT模式主要分为两个阶段：

如果TC收到的是回滚请求：

如果没问题，执行提交操作：

接下来，我们就需要从官网中去下载源码，下载地址：https://seata.io/zh-cn/blog/download.html，选择source即可，下载完成之后，通过IDEA打开项目。

源码下载下来之后，我们应该如何去找入口呢？首先我们需要找到对应引入的Seata包spring-alibaba-seata，我们在回想一下，我们开启事务的时候，是不是添加过一个@GlobalTransactional的注解，这个注解就是我们入手的一个点，我们在spring.factories中看到有一个GlobalTransactionAutoConfiguration，这个就是我们需要关注的点，也就是我们源码的入口。

在GlobalTransactionAutoConfiguration中我们找到一个用Bean注入的方法globalTransactionScanner，这个就是全局事务扫描器，这个类型主要负责加载配置，注入相关的Bean。

这里给大家展示了当前GlobalTransactionScanner的类关系图，其中我们现在继承了Aop的AbstractAutoProxyCreator类型，在这其中有一个重点方法，这个方法就是判断Bean对象是否需要代理，是否需要增强。

@Configuration@EnableConfigurationProperties(SeataProperties.class)public class GlobalTransactionAutoConfiguration {    //全局事务扫描器    @Bean    public GlobalTransactionScanner globalTransactionScanner() {      String applicationName = applicationContext.getEnvironment()          .getProperty("spring.application.name");      String txServiceGroup = seataProperties.getTxServiceGroup();      if (StringUtils.isEmpty(txServiceGroup)) {        txServiceGroup = applicationName + "-fescar-service-group";        seataProperties.setTxServiceGroup(txServiceGroup);      }      // 构建全局扫描器，传入参数：应用名、事务分组名，失败处理器      return new GlobalTransactionScanner(applicationName, txServiceGroup);    }}

在这其中我们要关心的是GlobalTransactionScanner这个类型，这个类型扫描@GlobalTransactional注解，并对代理方法进行拦截增强事务的功能。我们就从源码中搜索这个GlobalTransactionScanner类，看看里面具体是做了什么。

/** * The type Global transaction scanner. * 全局事务扫描器 * @author slievrly */public class GlobalTransactionScanner        //AbstractAutoProxyCreator AOP动态代理 增强Bean        extends AbstractAutoProxyCreator        /**         * ConfigurationChangeListener: 监听器基准接口         * InitializingBean： Bean初始化         * ApplicationContextAware： Spring容器         * DisposableBean： Spring 容器销毁         */        implements ConfigurationChangeListener, InitializingBean, ApplicationContextAware, DisposableBean {            private final String applicationId;//服务名    private final String txServiceGroup;//事务分组          private void initClient() {        //启动日志        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Initializing Global Transaction Clients ... ");        }        //检查应用名以及事务分组名，为空抛出异常IllegalArgumentException        if (DEFAULT_TX_GROUP_OLD.equals(txServiceGroup)) {            LOGGER.warn("the default value of seata.tx-service-group: {} has already changed to {} since Seata 1.5, " +                    "please change your default configuration as soon as possible " +                    "and we don"t recommend you to use default tx-service-group"s value provided by seata",                    DEFAULT_TX_GROUP_OLD, DEFAULT_TX_GROUP);        }        if (StringUtils.isNullOrEmpty(applicationId) || StringUtils.isNullOrEmpty(txServiceGroup)) {            throw new IllegalArgumentException(String.format("applicationId: %s, txServiceGroup: %s", applicationId, txServiceGroup));        }        //init TM        //初始化TM        TMClient.init(applicationId, txServiceGroup, accessKey, secretKey);        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Transaction Manager Client is initialized. applicationId[{}] txServiceGroup[{}]", applicationId, txServiceGroup);        }        //init RM        //初始化RM        RMClient.init(applicationId, txServiceGroup);        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Resource Manager is initialized. applicationId[{}] txServiceGroup[{}]", applicationId, txServiceGroup);        }        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Global Transaction Clients are initialized. ");        }        registerSpringShutdownHook();    }    @Override    public void afterPropertiesSet() {        if (disableGlobalTransaction) {            if (LOGGER.isInfoEnabled()) {                LOGGER.info("Global transaction is disabled.");            }            ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION,                    (ConfigurationChangeListener)this);            return;        }        if (initialized.compareAndSet(false, true)) {            initClient();        }    }      private void initClient() {        //启动日志        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Initializing Global Transaction Clients ... ");        }        //检查应用名以及事务分组名，为空抛出异常IllegalArgumentException        if (DEFAULT_TX_GROUP_OLD.equals(txServiceGroup)) {            LOGGER.warn("the default value of seata.tx-service-group: {} has already changed to {} since Seata 1.5, " +                    "please change your default configuration as soon as possible " +                    "and we don"t recommend you to use default tx-service-group"s value provided by seata",                    DEFAULT_TX_GROUP_OLD, DEFAULT_TX_GROUP);        }        //检查应用名以及事务分组名，为空抛出异常IllegalArgumentException        if (StringUtils.isNullOrEmpty(applicationId) || StringUtils.isNullOrEmpty(txServiceGroup)) {            throw new IllegalArgumentException(String.format("applicationId: %s, txServiceGroup: %s", applicationId, txServiceGroup));        }        //init TM        //初始化TM        TMClient.init(applicationId, txServiceGroup, accessKey, secretKey);        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Transaction Manager Client is initialized. applicationId[{}] txServiceGroup[{}]", applicationId, txServiceGroup);        }        //init RM        //初始化RM        RMClient.init(applicationId, txServiceGroup);        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Resource Manager is initialized. applicationId[{}] txServiceGroup[{}]", applicationId, txServiceGroup);        }        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Global Transaction Clients are initialized. ");        }        registerSpringShutdownHook();    }    //代理增强，Spring 所有的Bean都会经过这个方法    @Override    protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {        // do checkers        //检查bean和beanName        if (!doCheckers(bean, beanName)) {            return bean;        }        try {            //加锁防止并发            synchronized (PROXYED_SET) {                if (PROXYED_SET.contains(beanName)) {                    return bean;                }                interceptor = null;                //check TCC proxy                //检查是否为TCC模式                if (TCCBeanParserUtils.isTccAutoProxy(bean, beanName, applicationContext)) {                    // init tcc fence clean task if enable useTccFence                    //如果启用useTccFence 失败 ，则初始化TCC清理任务                    TCCBeanParserUtils.initTccFenceCleanTask(TCCBeanParserUtils.getRemotingDesc(beanName), applicationContext);                    //TCC interceptor, proxy bean of sofa:reference/dubbo:reference, and LocalTCC                    //如果是，添加TCC拦截器                    interceptor = new TccActionInterceptor(TCCBeanParserUtils.getRemotingDesc(beanName));                    ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION,                            (ConfigurationChangeListener)interceptor);                } else {                    //不是TCC                    Class serviceInterface = SpringProxyUtils.findTargetClass(bean);                    Class[] interfacesIfJdk = SpringProxyUtils.findInterfaces(bean);                    //判断是否有相关事务注解，如果没有不进行代理                    if (!existsAnnotation(new Class[]{serviceInterface})                        && !existsAnnotation(interfacesIfJdk)) {                        return bean;                    }                    //发现存在全局事务注解标注的Bean对象，添加拦截器                    if (globalTransactionalInterceptor == null) {                        //添加拦截器                        globalTransactionalInterceptor = new GlobalTransactionalInterceptor(failureHandlerHook);                        ConfigurationCache.addConfigListener(                                ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION,                                (ConfigurationChangeListener)globalTransactionalInterceptor);                    }                    interceptor = globalTransactionalInterceptor;                }                LOGGER.info("Bean[{}] with name [{}] would use interceptor [{}]", bean.getClass().getName(), beanName, interceptor.getClass().getName());                //检查是否为代理对象                if (!AopUtils.isAopProxy(bean)) {                    //不是代理对象，调用父级                    bean = super.wrapIfNecessary(bean, beanName, cacheKey);                } else {                    //是代理对象，反射获取代理类中已经存在的拦截器组合，然后添加到这个集合中                    AdvisedSupport advised = SpringProxyUtils.getAdvisedSupport(bean);                    Advisor[] advisor = buildAdvisors(beanName, getAdvicesAndAdvisorsForBean(null, null, null));                    int pos;                    for (Advisor avr : advisor) {                        // Find the position based on the advisor"s order, and add to advisors by pos                        pos = findAddSeataAdvisorPosition(advised, avr);                        advised.addAdvisor(pos, avr);                    }                }                PROXYED_SET.add(beanName);                return bean;            }        } catch (Exception exx) {            throw new RuntimeException(exx);        }    }}

InitializingBean：中实现了一个afterPropertiesSet()方法，在这个方法中，调用了initClient()。

AbstractAutoProxyCreator：APO动态代理，在之前的的Nacos和Sentiel中都有这个代理类，AOP在我们越往深入学习，在学习源码的会见到的越来越多，越来越重要，很多相关代理，都是通过AOP进行增强,在这个类中，我们需要关注有一个wrapIfNecessary()方法， 这个方法主要是判断被代理的bean或者类是否需要代理增强，在这个方法中会调用GlobalTransactionalInterceptor.invoke()进行带来增强。

具体代码如下：

public class GlobalTransactionalInterceptor implements ConfigurationChangeListener, MethodInterceptor, SeataInterceptor {    public GlobalTransactionalInterceptor(FailureHandler failureHandler) {        this.failureHandler = failureHandler == null ? DEFAULT_FAIL_HANDLER : failureHandler;        this.disable = ConfigurationFactory.getInstance().getBoolean(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION,            DEFAULT_DISABLE_GLOBAL_TRANSACTION);        this.order =            ConfigurationFactory.getInstance().getInt(ConfigurationKeys.TM_INTERCEPTOR_ORDER, TM_INTERCEPTOR_ORDER);        degradeCheck = ConfigurationFactory.getInstance().getBoolean(ConfigurationKeys.CLIENT_DEGRADE_CHECK,            DEFAULT_TM_DEGRADE_CHECK);        if (degradeCheck) {            ConfigurationCache.addConfigListener(ConfigurationKeys.CLIENT_DEGRADE_CHECK, this);            degradeCheckPeriod = ConfigurationFactory.getInstance()                .getInt(ConfigurationKeys.CLIENT_DEGRADE_CHECK_PERIOD, DEFAULT_TM_DEGRADE_CHECK_PERIOD);            degradeCheckAllowTimes = ConfigurationFactory.getInstance()                .getInt(ConfigurationKeys.CLIENT_DEGRADE_CHECK_ALLOW_TIMES, DEFAULT_TM_DEGRADE_CHECK_ALLOW_TIMES);            EVENT_BUS.register(this);            if (degradeCheckPeriod > 0 && degradeCheckAllowTimes > 0) {                startDegradeCheck();            }        }        this.initDefaultGlobalTransactionTimeout();    }    @Override    public Object invoke(final MethodInvocation methodInvocation) throws Throwable {        //获取执行的方法        Class targetClass =            methodInvocation.getThis() != null ? AopUtils.getTargetClass(methodInvocation.getThis()) : null;        Method specificMethod = ClassUtils.getMostSpecificMethod(methodInvocation.getMethod(), targetClass);        if (specificMethod != null && !specificMethod.getDeclaringClass().equals(Object.class)) {            final Method method = BridgeMethodResolver.findBridgedMethod(specificMethod);            //获取GlobalTransactional（全局事务）、GlobalLock(全局锁)元数据            final GlobalTransactional globalTransactionalAnnotation =                getAnnotation(method, targetClass, GlobalTransactional.class);            //GlobalLock会将本地事务的执行纳入Seata分布式事务的管理，共同竞争全局锁            //保证全局事务在执行的时候，本地事务不可以操作全局事务的记录            final GlobalLock globalLockAnnotation = getAnnotation(method, targetClass, GlobalLock.class);//获取全局锁            boolean localDisable = disable || (degradeCheck && degradeNum >= degradeCheckAllowTimes);            if (!localDisable) {                if (globalTransactionalAnnotation != null || this.aspectTransactional != null) {                    AspectTransactional transactional;                    if (globalTransactionalAnnotation != null) {                        transactional = new AspectTransactional(globalTransactionalAnnotation.timeoutMills(),                            globalTransactionalAnnotation.name(), globalTransactionalAnnotation.rollbackFor(),                            globalTransactionalAnnotation.noRollbackForClassName(),                            globalTransactionalAnnotation.noRollbackFor(),                            globalTransactionalAnnotation.noRollbackForClassName(),                            globalTransactionalAnnotation.propagation(),                            globalTransactionalAnnotation.lockRetryInterval(),                            globalTransactionalAnnotation.lockRetryTimes());                    } else {                        transactional = this.aspectTransactional;                    }                    //执行全局事务                    return handleGlobalTransaction(methodInvocation, transactional);                } else if (globalLockAnnotation != null) {                    //执行全局锁                    return handleGlobalLock(methodInvocation, globalLockAnnotation);                }            }        }        return methodInvocation.proceed();    }}

具体流程图如下所示：

在上面我们讲解到GlobalTransactionalInterceptor作为全局事务拦截器，一旦执行拦截，就会进入invoke方法，其中，我们会做@GlobalTransactional注解的判断，如果有这个注解的存在，会执行全局事务和全局锁，再执行全局事务的时候会调用handleGlobalTransaction全局事务处理器，获取事务信息，那我们接下来就来看一下GlobalTransactionalInterceptor.handleGlobalTransaction到底是如何执行全局事务的。

Object handleGlobalTransaction(final MethodInvocation methodInvocation,        final AspectTransactional aspectTransactional) throws Throwable {        boolean succeed = true;        try {            return transactionalTemplate.execute(new TransactionalExecutor() {                @Override                public Object execute() throws Throwable {                    return methodInvocation.proceed();                }                //获取事务名称，默认获取方法名                public String name() {                    String name = aspectTransactional.getName();                    if (!StringUtils.isNullOrEmpty(name)) {                        return name;                    }                    return formatMethod(methodInvocation.getMethod());                }                /**                 * 解析GlobalTransation注解属性，封装对对象                 * @return                 */                @Override                public TransactionInfo getTransactionInfo() {                    // reset the value of timeout                    //获取超时时间，默认60秒                    int timeout = aspectTransactional.getTimeoutMills();                    if (timeout <= 0 || timeout == DEFAULT_GLOBAL_TRANSACTION_TIMEOUT) {                        timeout = defaultGlobalTransactionTimeout;                    }                    //构建事务信息对象                    TransactionInfo transactionInfo = new TransactionInfo();                    transactionInfo.setTimeOut(timeout);//超时时间                    transactionInfo.setName(name());//事务名称                    transactionInfo.setPropagation(aspectTransactional.getPropagation());//事务传播                    transactionInfo.setLockRetryInterval(aspectTransactional.getLockRetryInterval());//校验或占用全局锁重试间隔                    transactionInfo.setLockRetryTimes(aspectTransactional.getLockRetryTimes());//校验或占用全局锁重试次数                    Set rollbackRules = new LinkedHashSet<>();                    //其他构建信息                    for (Class rbRule : aspectTransactional.getRollbackFor()) {                        rollbackRules.add(new RollbackRule(rbRule));                    }                    for (String rbRule : aspectTransactional.getRollbackForClassName()) {                        rollbackRules.add(new RollbackRule(rbRule));                    }                    for (Class rbRule : aspectTransactional.getNoRollbackFor()) {                        rollbackRules.add(new NoRollbackRule(rbRule));                    }                    for (String rbRule : aspectTransactional.getNoRollbackForClassName()) {                        rollbackRules.add(new NoRollbackRule(rbRule));                    }                    transactionInfo.setRollbackRules(rollbackRules);                    return transactionInfo;                }            });        } catch (TransactionalExecutor.ExecutionException e) {            //执行异常            TransactionalExecutor.Code code = e.getCode();            switch (code) {                case RollbackDone:                    throw e.getOriginalException();                case BeginFailure:                    succeed = false;                    failureHandler.onBeginFailure(e.getTransaction(), e.getCause());                    throw e.getCause();                case CommitFailure:                    succeed = false;                    failureHandler.onCommitFailure(e.getTransaction(), e.getCause());                    throw e.getCause();                case RollbackFailure:                    failureHandler.onRollbackFailure(e.getTransaction(), e.getOriginalException());                    throw e.getOriginalException();                case RollbackRetrying:                    failureHandler.onRollbackRetrying(e.getTransaction(), e.getOriginalException());                    throw e.getOriginalException();                default:                    throw new ShouldNeverHappenException(String.format("Unknown TransactionalExecutor.Code: %s", code));            }        } finally {            if (degradeCheck) {                EVENT_BUS.post(new DegradeCheckEvent(succeed));            }        }    }

在这里我们，主要关注一个重点方法execute()，这个方法主要用来执行事务的具体流程：

这个位置也是一个非常核心的一个位置，因为我们所有的业务进来以后都会去走这个位置，具体源码如下所示：

public Object execute(TransactionalExecutor business) throws Throwable {        // 1. Get transactionInfo        //获取事务信息        TransactionInfo txInfo = business.getTransactionInfo();        if (txInfo == null) {            throw new ShouldNeverHappenException("transactionInfo does not exist");        }        // 1.1 Get current transaction, if not null, the tx role is "GlobalTransactionRole.Participant".        //获取当前事务，主要获取XID        GlobalTransaction tx = GlobalTransactionContext.getCurrent();        // 1.2 Handle the transaction propagation.        //根据配置的不同事务传播行为，执行不同的逻辑        Propagation propagation = txInfo.getPropagation();        SuspendedResourcesHolder suspendedResourcesHolder = null;        try {            switch (propagation) {                case NOT_SUPPORTED:                    // If transaction is existing, suspend it.                    if (existingTransaction(tx)) {                        suspendedResourcesHolder = tx.suspend();                    }                    // Execute without transaction and return.                    return business.execute();                case REQUIRES_NEW:                    // If transaction is existing, suspend it, and then begin new transaction.                    if (existingTransaction(tx)) {                        suspendedResourcesHolder = tx.suspend();                        tx = GlobalTransactionContext.createNew();                    }                    // Continue and execute with new transaction                    break;                case SUPPORTS:                    // If transaction is not existing, execute without transaction.                    if (notExistingTransaction(tx)) {                        return business.execute();                    }                    // Continue and execute with new transaction                    break;                case REQUIRED:                    // If current transaction is existing, execute with current transaction,                    // else continue and execute with new transaction.                    break;                case NEVER:                    // If transaction is existing, throw exception.                    if (existingTransaction(tx)) {                        throw new TransactionException(                            String.format("Existing transaction found for transaction marked with propagation "never", xid = %s"                                    , tx.getXid()));                    } else {                        // Execute without transaction and return.                        return business.execute();                    }                case MANDATORY:                    // If transaction is not existing, throw exception.                    if (notExistingTransaction(tx)) {                        throw new TransactionException("No existing transaction found for transaction marked with propagation "mandatory"");                    }                    // Continue and execute with current transaction.                    break;                default:                    throw new TransactionException("Not Supported Propagation:" + propagation);            }            // 1.3 If null, create new transaction with role "GlobalTransactionRole.Launcher".            //如果当前事务为空，创建一个新的事务            if (tx == null) {                tx = GlobalTransactionContext.createNew();            }            // set current tx config to holder            GlobalLockConfig previousConfig = replaceGlobalLockConfig(txInfo);            try {                // 2. If the tx role is "GlobalTransactionRole.Launcher", send the request of beginTransaction to TC,                //    else do nothing. Of course, the hooks will still be triggered.                //开始执行全局事务                beginTransaction(txInfo, tx);                Object rs;                try {                    // Do Your Business                    // 执行当前业务逻辑                    //1、在TC注册当前分支事务，TC会在branch_table中插入一条分支事务数据                    //2、执行本地update语句，并在执行前后查询数据状态，并把数据前后镜像存入到undo_log中                    //3、远程调用其他应用，远程应用接收到XID，也会注册分支事务，写入branch_table以及本地undo_log表                    //4、会在lock_table表中插入全局锁数据（一个分支一条）                    rs = business.execute();                } catch (Throwable ex) {                    // 3. The needed business exception to rollback.                    //发生异常全局回滚，每个事务通过undo_log表进行事务补偿                    completeTransactionAfterThrowing(txInfo, tx, ex);                    throw ex;                }                // 4. everything is fine, commit.                //全局提交                commitTransaction(tx);                return rs;            } finally {                //5. clear                //清理所有资源                resumeGlobalLockConfig(previousConfig);                triggerAfterCompletion();                cleanUp();            }        } finally {            // If the transaction is suspended, resume it.            if (suspendedResourcesHolder != null) {                tx.resume(suspendedResourcesHolder);            }        }    }

这其中的第三步和第四步其实在向 TC（Seata-Server）发起全局事务的提交或者回滚，在这里我们首先关注执行全局事务的​​beginTransaction()​​方法。

// 向TC发起请求，采用模板模式    private void beginTransaction(TransactionInfo txInfo, GlobalTransaction tx) throws TransactionalExecutor.ExecutionException {        try {            triggerBeforeBegin();            //对TC发起请求            tx.begin(txInfo.getTimeOut(), txInfo.getName());            triggerAfterBegin();        } catch (TransactionException txe) {            throw new TransactionalExecutor.ExecutionException(tx, txe,                TransactionalExecutor.Code.BeginFailure);        }    }

在来关注其中，向TC发起请求的tx.begin()方法，而调用begin()方法的类为：DefaultGlobalTransaction。

@Override    public void begin(int timeout, String name) throws TransactionException {        //判断调用者是否为TM        if (role != GlobalTransactionRole.Launcher) {            assertXIDNotNull();            if (LOGGER.isDebugEnabled()) {                LOGGER.debug("Ignore Begin(): just involved in global transaction [{}]", xid);            }            return;        }        assertXIDNull();        String currentXid = RootContext.getXID();        if (currentXid != null) {            throw new IllegalStateException("Global transaction already exists," +                " can"t begin a new global transaction, currentXid = " + currentXid);        }        //获取XID        xid = transactionManager.begin(null, null, name, timeout);        status = GlobalStatus.Begin;        //绑定XID        RootContext.bind(xid);        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Begin new global transaction [{}]", xid);        }    }

再来看一下transactionManager.begin()方法，这个时候使用的是DefaultTransactionManager.begin默认的事务管理者，来获取XID，传入事务相关的信息 ，最好TC返回对应的全局事务XID，它调用的是DefaultTransactionManager.begin()方法。

public String begin(String applicationId, String transactionServiceGroup, String name, int timeout)        throws TransactionException {        GlobalBeginRequest request = new GlobalBeginRequest();        request.setTransactionName(name);        request.setTimeout(timeout);        //发送请求得到响应        GlobalBeginResponse response = (GlobalBeginResponse) syncCall(request);        if (response.getResultCode() == ResultCode.Failed) {            throw new TmTransactionException(TransactionExceptionCode.BeginFailed, response.getMsg());        }        //返回XID        return response.getXid();    }

在这里我们需要关注一个syncCall，在这里采用的是Netty通讯方式。

private AbstractTransactionResponse syncCall(AbstractTransactionRequest request) throws TransactionException {        try {            // 通过Netty发送请求            return (AbstractTransactionResponse) TmNettyRemotingClient.getInstance().sendSyncRequest(request);        } catch (TimeoutException toe) {            throw new TmTransactionException(TransactionExceptionCode.IO, "RPC timeout", toe);        }    }

具体图解如下：

在这里我们需要重点了解GlobalTransactionScanner这个类型，在这个类型中继承了一些接口和抽象类，这个类主要作用就是扫描有注解的Bean，并做AOP增强。

在上面的环节中，我们讲解了Seata AT模式2PC的执行流程，那么现在我们就来带大家了解一下关于AT数据源代理的信息，这也是AT模式中非常关键的一个重要知识点，大家可以拿起小本子，记下来。

首先AT模式的核心主要分为一下两个：

关于第一点我们已经分析清楚了，第二点就是关于AT模式如何解析SQL并写入undoLog中，但是在这之前，我们需要知道Seata是如何选择数据源，并进行数据源代理的。虽然全局事务拦截成功后最终还是执行了业务方法进行SQL提交和操作，但是由于Seata对数据源进行了代理，所以SQL的解析和undoLog的操作，是在数据源代理中进行完成的。

数据源代理是Seata中一个非常重要的知识点，在分布式事务运行过程中，undoLog的记录、资源的锁定，用户都是无感知的，因为这些操作都是数据源的代理中完成了，恰恰是这样，我们才要去了解，这样不仅有利于我们了解Seata的核心操作，还能对以后源码阅读有所帮助，因为其实很多底层代码都会去使用这样用户无感知的方式(代理)去实现。

同样，我们在之前的寻找源码入口的时候，通过我们项目中引入的jar找到一个SeataAutoConfiguration类，我们在里面找到一个SeataDataSourceBeanPostProcessor()，这个就是我们数据源代理的入口方法。

我们进入SeataDataSourceBeanPostProcessor类里面，发现继承了一个BeanPostProcessor,这个接口我们应该很熟悉，这个是Sprng的拓展接口，所有的Bean对象，都有进入两个方法postProcessAfterInitialization()和postProcessBeforeInitialization()这两个方法都是由BeanPostProcessor提供的，这两个方法，一个是初始化之前执行Before。一个是在初始化之后执行After，主要用来对比我们的的Bean是否为数据源代理对象。

在这里我们需要关注到一个postProcessAfterInitialization.proxyDataSource()方法，这个里面。

private Object proxyDataSource(Object originBean) {        DataSourceProxy dataSourceProxy = DataSourceProxyHolder.get().putDataSource((DataSource) originBean);        if (this.useJdkProxy) {            return Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), SpringProxyUtils.getAllInterfaces(originBean), (proxy, method, args) -> handleMethodProxy(dataSourceProxy, method, args, originBean));        } else {            return Enhancer.create(originBean.getClass(), (MethodInterceptor) (proxy, method, args, methodProxy) -> handleMethodProxy(dataSourceProxy, method, args, originBean));        }    }

这里有一个DataSourceProxy代理对象，我们需要看的就是这个类，这个就是我们数据库代理的对象，我们从我们下载的源码项目中，搜索这个代理对象，当我们打开这个类的目录时发现，除了这个，还有ConnectionProxy连接对象、StatementProxy、PreparedStatementProxySQL执行对象，这些都被Seata进行了代理，为什么要对这些都进行代理，代理的目的其实为了执行Seata的业务逻辑，生成undoLog，全局事务的开启，事务的提交回滚等操作。

DataSourceProxy具体做了什么，主要功能有哪些，我们来看一下。他在源码中是如何体现的，我们需要关注的是init()。

public class DataSourceProxy extends AbstractDataSourceProxy implements Resource {    private String resourceGroupId;    private void init(DataSource dataSource, String resourceGroupId) {        //资源组ID，默认是“default”这个默认值        this.resourceGroupId = resourceGroupId;        try (Connection connection = dataSource.getConnection()) {            //根据原始数据源得到JDBC连接和数据库类型            jdbcUrl = connection.getMetaData().getURL();            dbType = JdbcUtils.getDbType(jdbcUrl);            if (JdbcConstants.ORACLE.equals(dbType)) {                userName = connection.getMetaData().getUserName();            } else if (JdbcConstants.MARIADB.equals(dbType)) {                dbType = JdbcConstants.MYSQL;            }        } catch (SQLException e) {            throw new IllegalStateException("can not init dataSource", e);        }        initResourceId();        DefaultResourceManager.get().registerResource(this);        if (ENABLE_TABLE_META_CHECKER_ENABLE) {            //如果配置开关打开，会定时在线程池不断更新表的元数据缓存信息            tableMetaExecutor.scheduleAtFixedRate(() -> {                try (Connection connection = dataSource.getConnection()) {                    TableMetaCacheFactory.getTableMetaCache(DataSourceProxy.this.getDbType())                        .refresh(connection, DataSourceProxy.this.getResourceId());                } catch (Exception ignore) {                }            }, 0, TABLE_META_CHECKER_INTERVAL, TimeUnit.MILLISECONDS);        }        //Set the default branch type to "AT" in the RootContext.        RootContext.setDefaultBranchType(this.getBranchType());    }}

从上面我们可以看出，他主要做了以下几点的增强：

在这三个增强功能里面，第三个是最重要的，在AT模式里面，会自动记录undoLog，资源锁定，都是通过ConnectionProxy完成的，除此之外DataSrouceProxy重写了一个方法getConnection，因为这里返回的是一个ConnectionProxy，而不是原生的Connection。

@Override    public ConnectionProxy getConnection() throws SQLException {        Connection targetConnection = targetDataSource.getConnection();        return new ConnectionProxy(this, targetConnection);    }    @Override    public ConnectionProxy getConnection(String username, String password) throws SQLException {        Connection targetConnection = targetDataSource.getConnection(username, password);        return new ConnectionProxy(this, targetConnection);    }

ConnectionProxy继承AbstractConnectionProxy，在这个父类中有很多公用的方法，在这个父类有PreparedStatementProxy、StatementProxy、DataSourceProxy。

所以我们需要先来看一下AbstractConnectionProxy，因为这里封装了需要我们用到的通用方法和逻辑，在其中我们需要关注的主要在于PreparedStatementProxy和StatementProxy，在这里的逻辑主要是数据源连接的步骤，连接获取，创建执行对象等等。

@Override    public Statement createStatement() throws SQLException {        //调用真实连接对象获取Statement对象        Statement targetStatement = getTargetConnection().createStatement();        //创建Statement的代理        return new StatementProxy(this, targetStatement);    }       @Override    public PreparedStatement prepareStatement(String sql) throws SQLException {        //获取数据库类型 mysql/oracle        String dbType = getDbType();        // support oracle 10.2+        PreparedStatement targetPreparedStatement = null;        //如果是AT模式且开启全局事务        if (BranchType.AT == RootContext.getBranchType()) {            List sqlRecognizers = SQLVisitorFactory.get(sql, dbType);            if (sqlRecognizers != null && sqlRecognizers.size() == 1) {                SQLRecognizer sqlRecognizer = sqlRecognizers.get(0);                if (sqlRecognizer != null && sqlRecognizer.getSQLType() == SQLType.INSERT) {                    //获取表的元数据                    TableMeta tableMeta = TableMetaCacheFactory.getTableMetaCache(dbType).getTableMeta(getTargetConnection(),                            sqlRecognizer.getTableName(), getDataSourceProxy().getResourceId());                    //得到表的主键列名                    String[] pkNameArray = new String[tableMeta.getPrimaryKeyOnlyName().size()];                    tableMeta.getPrimaryKeyOnlyName().toArray(pkNameArray);                    targetPreparedStatement = getTargetConnection().prepareStatement(sql,pkNameArray);                }            }        }        if (targetPreparedStatement == null) {            targetPreparedStatement = getTargetConnection().prepareStatement(sql);        }        //创建PreparedStatementProxy代理        return new PreparedStatementProxy(this, targetPreparedStatement, sql);    }

在这两个代理对象中，都用到了以下几个方法：

@Overridepublic ResultSet executeQuery(String sql) throws SQLException {    this.targetSQL = sql;    return ExecuteTemplate.execute(this, (statement, args) -> statement.executeQuery((String) args[0]), sql);}@Overridepublic int executeUpdate(String sql) throws SQLException {    this.targetSQL = sql;    return ExecuteTemplate.execute(this, (statement, args) -> statement.executeUpdate((String) args[0]), sql);}@Overridepublic boolean execute(String sql) throws SQLException {    this.targetSQL = sql;    return ExecuteTemplate.execute(this, (statement, args) -> statement.execute((String) args[0]), sql);}

在这些方法中都调用了ExecuteTemplate.execute()，所以我们就看一下在ExecuteTemplate类中具体是做了什么操作：

public class ExecuteTemplate {    public static  T execute(List sqlRecognizers,                                                     StatementProxy statementProxy,                                                     StatementCallback statementCallback,                                                     Object... args) throws SQLException {        //如果没有全局锁，并且不是AT模式，直接执行SQL        if (!RootContext.requireGlobalLock() && BranchType.AT != RootContext.getBranchType()) {            // Just work as original statement            return statementCallback.execute(statementProxy.getTargetStatement(), args);        }        //得到数据库类型- mysql/oracle        String dbType = statementProxy.getConnectionProxy().getDbType();        if (CollectionUtils.isEmpty(sqlRecognizers)) {            //sqlRecognizers 为SQL语句的解析器，获取执行的SQL，通过它可以获得SQL语句表名、相关的列名、类型等信息，最后解析出对应的SQL表达式            sqlRecognizers = SQLVisitorFactory.get(                    statementProxy.getTargetSQL(),                    dbType);        }        Executor executor;        if (CollectionUtils.isEmpty(sqlRecognizers)) {            //如果seata没有找到合适的SQL语句解析器，那么便创建简单执行器PlainExecutor            //PlainExecutor直接使用原生的Statment对象执行SQL            executor = new PlainExecutor<>(statementProxy, statementCallback);        } else {            if (sqlRecognizers.size() == 1) {                SQLRecognizer sqlRecognizer = sqlRecognizers.get(0);                switch (sqlRecognizer.getSQLType()) {                    //新增                    case INSERT:                        executor = EnhancedServiceLoader.load(InsertExecutor.class, dbType,                                    new Class[]{StatementProxy.class, StatementCallback.class, SQLRecognizer.class},                                    new Object[]{statementProxy, statementCallback, sqlRecognizer});                        break;                        //修改                    case UPDATE:                        executor = new UpdateExecutor<>(statementProxy, statementCallback, sqlRecognizer);                        break;                        //删除                    case DELETE:                        executor = new DeleteExecutor<>(statementProxy, statementCallback, sqlRecognizer);                        break;                        //加锁                    case SELECT_FOR_UPDATE:                        executor = new SelectForUpdateExecutor<>(statementProxy, statementCallback, sqlRecognizer);                        break;                        //插入加锁                    case INSERT_ON_DUPLICATE_UPDATE:                        switch (dbType) {                            case JdbcConstants.MYSQL:                            case JdbcConstants.MARIADB:                                executor =                                    new MySQLInsertOrUpdateExecutor(statementProxy, statementCallback, sqlRecognizer);                                break;                            default:                                throw new NotSupportYetException(dbType + " not support to INSERT_ON_DUPLICATE_UPDATE");                        }                        break;                        //原生                    default:                        executor = new PlainExecutor<>(statementProxy, statementCallback);                        break;                }            } else {                //批量处理SQL语句                executor = new MultiExecutor<>(statementProxy, statementCallback, sqlRecognizers);            }        }        T rs;        try {            //执行            rs = executor.execute(args);        } catch (Throwable ex) {            if (!(ex instanceof SQLException)) {                // Turn other exception into SQLException                ex = new SQLException(ex);            }            throw (SQLException) ex;        }        return rs;    }}

在ExecuteTemplate就一个execute()，Seata将SQL执行委托给不同的执行器(模板)，Seata提供了6种执行器也就是我们代码 case 中（INSERT，UPDATE，DELETE，SELECT_FOR_UPDATE,INSERT_ON_DUPLICATE_UPDATE），这些执行器的父类都是AbstractDMLBaseExecutor。

@Override    public T execute(Object... args) throws Throwable {        String xid = RootContext.getXID();        if (xid != null) {            //获取XID            statementProxy.getConnectionProxy().bind(xid);        }        //设置全局锁        statementProxy.getConnectionProxy().setGlobalLockRequire(RootContext.requireGlobalLock());        return doExecute(args);    }

@Override    public T doExecute(Object... args) throws Throwable {        AbstractConnectionProxy connectionProxy = statementProxy.getConnectionProxy();        //是否自动提交        if (connectionProxy.getAutoCommit()) {            return executeAutoCommitTrue(args);        } else {            return executeAutoCommitFalse(args);        }    }

protected T executeAutoCommitTrue(Object[] args) throws Throwable {        ConnectionProxy connectionProxy = statementProxy.getConnectionProxy();        try {            //设置为手动提交            connectionProxy.changeAutoCommit();            return new LockRetryPolicy(connectionProxy).execute(() -> {                //调用手动提交方法，得到分支执行的最终结果                T result = executeAutoCommitFalse(args);                //执行提交                connectionProxy.commit();                return result;            });        } catch (Exception e) {            // when exception occur in finally,this exception will lost, so just print it here            LOGGER.error("execute executeAutoCommitTrue error:{}", e.getMessage(), e);            if (!LockRetryPolicy.isLockRetryPolicyBranchRollbackOnConflict()) {                connectionProxy.getTargetConnection().rollback();            }            throw e;        } finally {            connectionProxy.getContext().reset();            connectionProxy.setAutoCommit(true);        }    }

protected T executeAutoCommitFalse(Object[] args) throws Exception {        if (!JdbcConstants.MYSQL.equalsIgnoreCase(getDbType()) && isMultiPk()) {            throw new NotSupportYetException("multi pk only support mysql!");        }        //获取前镜像        TableRecords beforeImage = beforeImage();        //执行具体业务        T result = statementCallback.execute(statementProxy.getTargetStatement(), args);        //获取执行数量        int updateCount = statementProxy.getUpdateCount();        //判断如果执行数量大于0        if (updateCount > 0) {            //获取后镜像            TableRecords afterImage = afterImage(beforeImage);            //暂存到undolog中，在Commit的时候保存到数据库            prepareUndoLog(beforeImage, afterImage);        }        return result;    }

@Override    public void commit() throws SQLException {        try {            lockRetryPolicy.execute(() -> {                //具体执行                doCommit();                return null;            });        } catch (SQLException e) {            if (targetConnection != null && !getAutoCommit() && !getContext().isAutoCommitChanged()) {                rollback();            }            throw e;        } catch (Exception e) {            throw new SQLException(e);        }    }

private void doCommit() throws SQLException {        //判断是否存在全局事务        if (context.inGlobalTransaction()) {            processGlobalTransactionCommit();        } else if (context.isGlobalLockRequire()) {            processLocalCommitWithGlobalLocks();        } else {            targetConnection.commit();        }    }

private void processGlobalTransactionCommit() throws SQLException {        try {            //注册分支事务            register();        } catch (TransactionException e) {            recognizeLockKeyConflictException(e, context.buildLockKeys());        }        try {            //写入数据库undolog            UndoLogManagerFactory.getUndoLogManager(this.getDbType()).flushUndoLogs(this);            //执行原生提交 一阶段提交            targetConnection.commit();        } catch (Throwable ex) {            LOGGER.error("process connectionProxy commit error: {}", ex.getMessage(), ex);            report(false);            throw new SQLException(ex);        }        if (IS_REPORT_SUCCESS_ENABLE) {            report(true);        }        context.reset();    }

//注册分支事务，生成分支事务ID    private void register() throws TransactionException {        if (!context.hasUndoLog() || !context.hasLockKey()) {            return;        }        //注册分支事务        Long branchId = DefaultResourceManager.get().branchRegister(BranchType.AT, getDataSourceProxy().getResourceId(),            null, context.getXid(), context.getApplicationData(), context.buildLockKeys());        context.setBranchId(branchId);    }

@Override    public void flushUndoLogs(ConnectionProxy cp) throws SQLException {        ConnectionContext connectionContext = cp.getContext();        if (!connectionContext.hasUndoLog()) {            return;        }        //获取XID        String xid = connectionContext.getXid();        //获取分支ID        long branchId = connectionContext.getBranchId();        BranchUndoLog branchUndoLog = new BranchUndoLog();        branchUndoLog.setXid(xid);        branchUndoLog.setBranchId(branchId);        branchUndoLog.setSqlUndoLogs(connectionContext.getUndoItems());        UndoLogParser parser = UndoLogParserFactory.getInstance();        byte[] undoLogContent = parser.encode(branchUndoLog);        if (LOGGER.isDebugEnabled()) {            LOGGER.debug("Flushing UNDO LOG: {}", new String(undoLogContent, Constants.DEFAULT_CHARSET));        }        CompressorType compressorType = CompressorType.NONE;        if (needCompress(undoLogContent)) {            compressorType = ROLLBACK_INFO_COMPRESS_TYPE;            undoLogContent = CompressorFactory.getCompressor(compressorType.getCode()).compress(undoLogContent);        }        //写入数据库具体位置        insertUndoLogWithNormal(xid, branchId, buildContext(parser.getName(), compressorType), undoLogContent, cp.getTargetConnection());    }

@Override    protected void insertUndoLogWithNormal(String xid, long branchId, String rollbackCtx, byte[] undoLogContent,                                           Connection conn) throws SQLException {        insertUndoLog(xid, branchId, rollbackCtx, undoLogContent, State.Normal, conn);    }           //具体写入操作    private void insertUndoLog(String xid, long branchId, String rollbackCtx, byte[] undoLogContent,                               State state, Connection conn) throws SQLException {        try (PreparedStatement pst = conn.prepareStatement(INSERT_UNDO_LOG_SQL)) {            pst.setLong(1, branchId);            pst.setString(2, xid);            pst.setString(3, rollbackCtx);            pst.setBytes(4, undoLogContent);            pst.setInt(5, state.getValue());            pst.executeUpdate();        } catch (Exception e) {            if (!(e instanceof SQLException)) {                e = new SQLException(e);            }            throw (SQLException) e;        }    }

//默认协调者        DefaultCoordinator coordinator = DefaultCoordinator.getInstance(nettyRemotingServer);

//处理全局事务    @Override    protected void doGlobalBegin(GlobalBeginRequest request, GlobalBeginResponse response, RpcContext rpcContext)            throws TransactionException {        //响应客户端xid        response.setXid(core.begin(rpcContext.getApplicationId(), rpcContext.getTransactionServiceGroup(),                request.getTransactionName(), request.getTimeout()));        if (LOGGER.isInfoEnabled()) {            LOGGER.info("Begin new global transaction applicationId: {},transactionServiceGroup: {}, transactionName: {},timeout:{},xid:{}",                    rpcContext.getApplicationId(), rpcContext.getTransactionServiceGroup(), request.getTransactionName(), request.getTimeout(), response.getXid());        }    }            //处理全局提交    @Override    protected void doGlobalCommit(GlobalCommitRequest request, GlobalCommitResponse response, RpcContext rpcContext)            throws TransactionException {        MDC.put(RootContext.MDC_KEY_XID, request.getXid());        response.setGlobalStatus(core.commit(request.getXid()));    }    //处理全局回滚    @Override    protected void doGlobalRollback(GlobalRollbackRequest request, GlobalRollbackResponse response,                                    RpcContext rpcContext) throws TransactionException {        MDC.put(RootContext.MDC_KEY_XID, request.getXid());        response.setGlobalStatus(core.rollback(request.getXid()));    }

@Override    public String begin(String applicationId, String transactionServiceGroup, String name, int timeout)        throws TransactionException {        //创建全局事务Session        GlobalSession session = GlobalSession.createGlobalSession(applicationId, transactionServiceGroup, name,            timeout);        MDC.put(RootContext.MDC_KEY_XID, session.getXid());        //为Session重添加回调监听，SessionHolder.getRootSessionManager() 获取一个全局Session管理器DataBaseSessionManager        //观察者设计模式，创建DataBaseSessionManager        session.addSessionLifecycleListener(SessionHolder.getRootSessionManager());        //全局事务开始        session.begin();        // transaction start event        MetricsPublisher.postSessionDoingEvent(session, false);        return session.getXid();    }

/**     * Gets root session manager.     * 获取一个全局Session管理器     * @return the root session manager     */    public static SessionManager getRootSessionManager() {        if (ROOT_SESSION_MANAGER == null) {            throw new ShouldNeverHappenException("SessionManager is NOT init!");        }        return ROOT_SESSION_MANAGER;    }           public static void init(String mode) {        if (StringUtils.isBlank(mode)) {            mode = CONFIG.getConfig(ConfigurationKeys.STORE_SESSION_MODE,                    CONFIG.getConfig(ConfigurationKeys.STORE_MODE, SERVER_DEFAULT_STORE_MODE));        }        StoreMode storeMode = StoreMode.get(mode);        //判断Seata模式，当前为DB        if (StoreMode.DB.equals(storeMode)) {            //通过SPI机制读取SessionManager接口实现类，读取的META-INF.services目录，在通过反射机制创建对象DataBaseSessionManager            ROOT_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.DB.getName());            ........        }    }

@Override    public void begin() throws TransactionException {        //声明全局事务开始        this.status = GlobalStatus.Begin;        //开始时间        this.beginTime = System.currentTimeMillis();        //激活全局事务        this.active = true;        //将SessionManager放入到集合中，调用onBegin方法        for (SessionLifecycleListener lifecycleListener : lifecycleListeners) {            //调用父级抽象类的方法            lifecycleListener.onBegin(this);        }    }

@Override    public void onBegin(GlobalSession globalSession) throws TransactionException {        //这里调用的是DateBaseSessionManager        addGlobalSession(globalSession);    }           @Override    public void addGlobalSession(GlobalSession session) throws TransactionException {        if (StringUtils.isBlank(taskName)) {            //写入session            boolean ret = transactionStoreManager.writeSession(LogOperation.GLOBAL_ADD, session);            if (!ret) {                throw new StoreException("addGlobalSession failed.");            }        } else {            boolean ret = transactionStoreManager.writeSession(LogOperation.GLOBAL_UPDATE, session);            if (!ret) {                throw new StoreException("addGlobalSession failed.");            }        }    }

@Override    public boolean writeSession(LogOperation logOperation, SessionStorable session) {        //第一次进入是写入 会进入当前方法        //全局添加        if (LogOperation.GLOBAL_ADD.equals(logOperation)) {            return logStore.insertGlobalTransactionDO(SessionConverter.convertGlobalTransactionDO(session));            //全局修改        } else if (LogOperation.GLOBAL_UPDATE.equals(logOperation)) {            return logStore.updateGlobalTransactionDO(SessionConverter.convertGlobalTransactionDO(session));            //全局删除        } else if (LogOperation.GLOBAL_REMOVE.equals(logOperation)) {            return logStore.deleteGlobalTransactionDO(SessionConverter.convertGlobalTransactionDO(session));            //分支添加        } else if (LogOperation.BRANCH_ADD.equals(logOperation)) {            return logStore.insertBranchTransactionDO(SessionConverter.convertBranchTransactionDO(session));            //分支更新        } else if (LogOperation.BRANCH_UPDATE.equals(logOperation)) {            return logStore.updateBranchTransactionDO(SessionConverter.convertBranchTransactionDO(session));            //分支移除        } else if (LogOperation.BRANCH_REMOVE.equals(logOperation)) {            return logStore.deleteBranchTransactionDO(SessionConverter.convertBranchTransactionDO(session));        } else {            throw new StoreException("Unknown LogOperation:" + logOperation.name());        }    }

@Override    public boolean insertGlobalTransactionDO(GlobalTransactionDO globalTransactionDO) {        String sql = LogStoreSqlsFactory.getLogStoreSqls(dbType).getInsertGlobalTransactionSQL(globalTable);        Connection conn = null;        PreparedStatement ps = null;        try {            int index = 1;            conn = logStoreDataSource.getConnection();            conn.setAutoCommit(true);            ps = conn.prepareStatement(sql);            ps.setString(index++, globalTransactionDO.getXid());            ps.setLong(index++, globalTransactionDO.getTransactionId());            ps.setInt(index++, globalTransactionDO.getStatus());            ps.setString(index++, globalTransactionDO.getApplicationId());            ps.setString(index++, globalTransactionDO.getTransactionServiceGroup());            String transactionName = globalTransactionDO.getTransactionName();            transactionName = transactionName.length() > transactionNameColumnSize ?                transactionName.substring(0, transactionNameColumnSize) :                transactionName;            ps.setString(index++, transactionName);            ps.setInt(index++, globalTransactionDO.getTimeout());            ps.setLong(index++, globalTransactionDO.getBeginTime());            ps.setString(index++, globalTransactionDO.getApplicationData());            return ps.executeUpdate() > 0;        } catch (SQLException e) {            throw new StoreException(e);        } finally {            IOUtil.close(ps, conn);        }    }