Spring事務的開啟原理詳解
- 在事務配置類上聲明@EnableTransactionManagement註解開啟事務
- 在事務配置類上定義數據源
- 在事務配置類上定義事務管理器
- 在相關類或者方法上使用@Transactional聲明事務
代碼如下:
@Configuration @EnableTransactionManagement public class RootConfig{ @Bean public DataSource dataSource(){ DruidDataSource dataSource = new DruidDataSource(); dataSource.setXXX(); ... return dataSource; } @Bean public PlatfromTransactionManager txManager(){ return new DataSourceTransactionManager(dataSource()); } }
@Service public class UserService{ @Autowired private UserRepository userRepository; @Transactional public void addUser(User user){ userRepository.save(user); } }
@EnableTransactionManagement開啟事務原理解析
@EnableTransactionManagement源碼如下:
@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 Ordered.LOWEST_PRECEDENCE; }
可以看到,@EnableTransactionManagement接口類主要Import瞭TransactionManagementConfigurationSelector來實現其註入,而TransactionManagementConfigurationSelector又主要使用selectImport方法來實現其註入,代碼如下:
@Override public final String[] selectImports(AnnotationMetadata importingClassMetadata) { Class<?> annoType = GenericTypeResolver.resolveTypeArgument(getClass(), AdviceModeImportSelector.class); AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(importingClassMetadata, annoType); if (attributes == null) { throw new IllegalArgumentException(String.format( "@%s is not present on importing class '%s' as expected", annoType.getSimpleName(), importingClassMetadata.getClassName())); } AdviceMode adviceMode = attributes.getEnum(this.getAdviceModeAttributeName()); //根據AdviceMode返回不同的類型,默認是AdviceMode.PROXY。 String[] imports = selectImports(adviceMode); if (imports == null) { throw new IllegalArgumentException(String.format("Unknown AdviceMode: '%s'", adviceMode)); } return imports; } @Override protected String[] selectImports(AdviceMode adviceMode) { switch (adviceMode) { case PROXY: return new String[] {AutoProxyRegistrar.class.getName(), ProxyTransactionManagementConfiguration.class.getName()}; case ASPECTJ: return new String[] {TransactionManagementConfigUtils.TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME}; default: return null; } }
其中主要功能點為根據AdviceMode選擇創建不同的bean,AdviceMode的默認代理方式是PROXY,jdk代理。所以返回的是AutoProxyRegistrar和ProxyTransactionManagementConfiguration。
我們先分析AutoProxyRegistrar,AutoProxyRegistrar實現瞭ImportBeanDefinitionRegistrar,那在創建bean的時候會調用registerBeanDefinitions方法。registerBeanDefinitions方法的實現:
@Override public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { boolean candidateFound = false; Set<String> annoTypes = importingClassMetadata.getAnnotationTypes(); for (String annoType : annoTypes) { AnnotationAttributes candidate = AnnotationConfigUtils.attributesFor(importingClassMetadata, annoType); if (candidate == null) { continue; } Object mode = candidate.get("mode"); Object proxyTargetClass = candidate.get("proxyTargetClass"); if (mode != null && proxyTargetClass != null && AdviceMode.class == mode.getClass() && Boolean.class == proxyTargetClass.getClass()) { candidateFound = true; //隻有@EnableTransactionManagement註解才會走到這裡 if (mode == AdviceMode.PROXY) { AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry); if ((Boolean) proxyTargetClass) { AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry); return; } } } } //... } public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) { return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source); }
可以看到,它通過註冊InfrastructureAdvisorAutoProxyCreator來啟動Spring Aop。
接下來再看ProxyTransactionManagementConfiguration的作用,代碼如下:
@Configuration public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration { @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; } @Bean @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public TransactionAttributeSource transactionAttributeSource() { return new AnnotationTransactionAttributeSource(); } @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; } }
ProxyTransactionManagementConfiguration是一個配置文件,註冊瞭三個bean,BeanFactoryTransactionAttributeSourceAdvisor、AnnotationTransactionAttributeSource、TransactionInterceptor,而這三個類分別繼承Advisor、Advice和Pointcut。即切面所需組件。
總結
@EnableTransactionManagement利用AutoProxyRegistrar啟動Spring Aop,使用ProxyTransactionManagementConfiguration配置對應切面部件。
以上就是Spring事務的簡單實現步驟的詳細內容,更多關於Spring事務實現步驟的資料請關註WalkonNet其它相關文章!
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