分库分表之ShardingSphere 支持分布式事务源码分析

旧城等待， 2023-06-25 04:51 22阅读 0赞

1. 事务相关配置

>     @EnableTransactionManagement  // 支持spring事务
>     @SpringBootApplication(scanBasePackages = "com.example.shard")
>     public class ShardJdbcApplication {
> 
>   .....
> 
> \}

>  
> 
> @ShardingTransactionType(TransactionType.XA)  // 执行shardsphere的分布式事务
> 
> @Transactional(rollbackFor = Exception.class)  // 该方法开启事务
> 
> @Override
> 
> public int insert()\{
> 
> ...
> 
> \}

2.  EnableTransactionManagement注解分析

>     @Target({ElementType.TYPE})
>     @Retention(RetentionPolicy.RUNTIME)
>     @Documented
>     @Import({TransactionManagementConfigurationSelector.class})
>     public @interface EnableTransactionManagement {
>         boolean proxyTargetClass() default false;
>     
>         AdviceMode mode() default AdviceMode.PROXY;
>     
>         int order() default 2147483647;
>     }

该注解主要依赖@Import中指定的类TransactionManagementConfigurationSelector来实现

TransactionManagementConfigurationSelector源码如下：

>  
> 
>     public class TransactionManagementConfigurationSelector extends AdviceModeImportSelector<EnableTransactionManagement> {
>         public TransactionManagementConfigurationSelector() {
>         }
>     
>         protected String[] selectImports(AdviceMode adviceMode) {
>             switch(adviceMode) {
>             case PROXY:
>                 return new String[]{AutoProxyRegistrar.class.getName(), ProxyTransactionManagementConfiguration.class.getName()};
>             case ASPECTJ:
>                 return new String[]{"org.springframework.transaction.aspectj.AspectJTransactionManagementConfiguration"};
>             default:
>                 return null;
>             }
>         }
>     }

debug发现默认使用的adviceMode为PROXY

![20191226091326452.png][]

然后加载两个类 AutoProxyRegistrar和ProxyTransactionManagementConfiguration

ProxyTransactionManagementConfiguration分析

>     @Bean(
>         name = {"org.springframework.transaction.config.internalTransactionAdvisor"}
>     )
>     @Role(2)
>     public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor() {
>         BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor();
>         advisor.setTransactionAttributeSource(this.transactionAttributeSource());
>         advisor.setAdvice(this.transactionInterceptor());
>         advisor.setOrder((Integer)this.enableTx.getNumber("order"));
>         return advisor;
>     }
>     
>     @Bean
>     @Role(2)
>     public TransactionAttributeSource transactionAttributeSource() {
>         return new AnnotationTransactionAttributeSource();
>     }
>     
>     @Bean
>     @Role(2)
>     public TransactionInterceptor transactionInterceptor() {
>         TransactionInterceptor interceptor = new TransactionInterceptor();
>         interceptor.setTransactionAttributeSource(this.transactionAttributeSource());
>         if (this.txManager != null) {
>             interceptor.setTransactionManager(this.txManager);
>         }
>     
>         return interceptor;
>     }

3. 解析流程

debug发现从

AbstractApplicationContext 开始进入

>  
> 
>     public void refresh() throws BeansException, IllegalStateException {
>         Object var1 = this.startupShutdownMonitor;
>         synchronized(this.startupShutdownMonitor) {
>             this.prepareRefresh();
>             ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
>             this.prepareBeanFactory(beanFactory);
>     
>             try {
>                 this.postProcessBeanFactory(beanFactory);
>                 // 解析自动导入的类
>                 this.invokeBeanFactoryPostProcessors(beanFactory);
>                 this.registerBeanPostProcessors(beanFactory);
>                 this.initMessageSource();
>                 this.initApplicationEventMulticaster();
>                 this.onRefresh();
>                 this.registerListeners();
>                 this.finishBeanFactoryInitialization(beanFactory);
>                 this.finishRefresh();

PostProcessorRegistrationDelegate -->

invokeBeanDefinitionRegistryPostProcessors() -->

解析的入口为ConfiguratuonClassPostProccessor的postProcessBeanDefinitionRegistry-->

processConfigurationDefinitions方法

具体解析Import的类为ConfigurationClassParser

解析路径为process--> processGroupImports-->processImports --> proccessConfigurationClass --> doProcessConfigurationClass

4. 事务处理流程（多个数据源）

DataSourceTransactionManager类

1） 根据Service方法上的Transactional注解生成代理类，执行这个方法之前，先走代理逻辑，也就是事务逻辑

2） 第一步获取事务doGetTransaction

3) 第二步开始执行事务 doBegin, 这一步会将connection提交方式设置为手动提交

4）第三步 执行doCommit