一、SEATA CLIENT

2022-05-12 20:59:23   6  举报

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seata客户端源码解析--seata全局事务处理 1、首先，通过SpringBoot的自动配置，加载配置类SeataAutoConfiguration，在该类中创建bean GlobalTransactionScanner ; 2、GlobalTransactionScanner 类实现了接口AbstractAutoProxyCreator，AbstractAutoProxyCreator接口实现了方法SmartInstantiationAwareBeanPostProcessor，在方法postProcessAfterInitialization调用了方法wrapIfNecessary(Object bean, String beanName, Object cacheKey)，而在类GlobalTransactionScanner 中重写了方法wrapIfNecessary(Object bean, String beanName, Object cacheKey)，从而给容器中相关的bean进行代理。 3、GlobalTransactionScanner 实现了InitializingBean接口，实现了方法afterPropertiesSet()，在该方法中初始化TM和RM客户端，从而与TC进行通信，进行事务的发起，提交与回滚。 4、在GlobalTransactionScanner 类中的wrapIfNecessary(）方法中，生成一个拦截器GlobalTransactionalInterceptor(); 5、在GlobalTransactionScanner 类的invoke(final MethodInvocation methodInvocation)方法中，会先判断执行的代理类的方法上是否存在全局事务注解@GlobalTransactional没存在则处理全局事务handleGlobalTransaction(methodInvocation, globalTransactionalAnnotation);，否则是否存@GlobalLock，则处理全局锁，否则，则为普通方法，直接执行方法内容。 6、在方法handleGlobalTransaction(methodInvocation, globalTransactionalAnnotation);中，会开启全局事务，执行业务逻辑，回滚事务，提交事务等，最终会通过第三步中的初始化的客户端，与TC进行全局事务的开启，提交，回滚等。

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# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=io.seata.spring.boot.autoconfigure.SeataAutoConfiguration

进入类：SeataAutoConfiguration，SeataAutoConfiguration配置类，创建bean:GlobalTransactionScanner
@Bean
    @DependsOn({BEAN_NAME_SPRING_APPLICATION_CONTEXT_PROVIDER})
    @ConditionalOnMissingBean(GlobalTransactionScanner.class)
    public GlobalTransactionScanner globalTransactionScanner(SeataProperties seataProperties) {
        if (LOGGER.isInfoEnabled()) {
            LOGGER.info("Automatically configure Seata");
        }
        return new GlobalTransactionScanner(seataProperties.getApplicationId(), seataProperties.getTxServiceGroup());
    }

该类继承类：AbstractAutoProxyCreator

重写方法：wrapIfNecessary(Object bean, String beanName, Object cacheKey)

1、校验是否是TCC模式代理，若不是进行下一步

2、获取一个全局事务的拦截器：interceptor = new GlobalTransactionalInterceptor(failureHandlerHook);

进入类：GlobalTransactionalInterceptor 该类实现接口MethodInterceptor，执行invoke(final MethodInvocation methodInvocation) 方法

1、获取@GlobalTransactional注解：GlobalTransactional globalTransactionalAnnotation = getAnnotation(method, GlobalTransactional.class);

2、如果方法上存在@GlobalTransactional注解注解，则开始全局事务处理：if (!disable && globalTransactionalAnnotation != null) { return handleGlobalTransaction(methodInvocation, globalTransactionalAnnotation); }

进入方法handleGlobalTransaction(final MethodInvocation methodInvocation,
final GlobalTransactional globalTrxAnno)

进入核心类TransactionalTemplate transactionalTemplate = new TransactionalTemplate() 的execute()核心方法

1、入参为：new TransactionalExecutor() {
                @Override
                public Object execute() throws Throwable {
                    return methodInvocation.proceed();
                }

                public String name() {
                    String name = globalTrxAnno.name();
                    if (!StringUtils.isNullOrEmpty(name)) {
                        return name;
                    }
                    return formatMethod(methodInvocation.getMethod());
                }

                @Override
                public TransactionInfo getTransactionInfo() {
                    TransactionInfo transactionInfo = new TransactionInfo();
                    transactionInfo.setTimeOut(globalTrxAnno.timeoutMills());
                    transactionInfo.setName(name());
                    Set<RollbackRule> rollbackRules = new LinkedHashSet<>();
                    for (Class<?> rbRule : globalTrxAnno.rollbackFor()) {
                        rollbackRules.add(new RollbackRule(rbRule));
                    }
                    for (String rbRule : globalTrxAnno.rollbackForClassName()) {
                        rollbackRules.add(new RollbackRule(rbRule));
                    }
                    for (Class<?> rbRule : globalTrxAnno.noRollbackFor()) {
                        rollbackRules.add(new NoRollbackRule(rbRule));
                    }
                    for (String rbRule : globalTrxAnno.noRollbackForClassName()) {
                        rollbackRules.add(new NoRollbackRule(rbRule));
                    }
                    transactionInfo.setRollbackRules(rollbackRules);
                    return transactionInfo;
                }
            }

2、public Object execute(TransactionalExecutor business)

1、 get or create a transaction 获取或者创建一个全局事务 GlobalTransaction tx = GlobalTransactionContext.getCurrentOrCreate();

getCurrentOrCreate()

2、// 2. get transactionInfo 获取事务信息 TransactionInfo txInfo = business.getTransactionInfo();

getTransactionInfo()

3、begin transaction 开启事务 beginTransaction(txInfo, tx);

private void beginTransaction(TransactionInfo txInfo, GlobalTransaction tx)

4、Do Your Business，执行业务逻辑 rs = business.execute();

execute()

5、the needed business exception to rollback. 回滚事 completeTransactionAfterThrowing(txInfo,tx,ex);

TransactionalTemplate#completeTransactionAfterThrowing

6、everything is fine, commit. 无异常方式，提交事务 commitTransaction(tx);