Spring5.x Transaction 自定义事务标签
1、自定义事务标签XML配置
2、自定义事务标签命名空间处理器 TxNamespaceHandler
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());
}
}
3、自定义事务标签解析器 AnnotationDrivenBeanDefinitionParser
3.1 解析{@code
public BeanDefinition parse(Element element, ParserContext parserContext) {
// 注册事务事件监听器
registerTransactionalEventListenerFactory(parserContext);
String mode = element.getAttribute("mode");
if ("aspectj".equals(mode)) {
// mode="aspectj" AspectJ方式进行事物切入
registerTransactionAspect(element, parserContext);
if (ClassUtils.isPresent("javax.transaction.Transactional", getClass().getClassLoader())) {
registerJtaTransactionAspect(element, parserContext);
}
}
else {
// mode="proxy" Spring Aop方式进行事物切入
AopAutoProxyConfigurer.configureAutoProxyCreator(element, parserContext);
}
return null;
}
3.2 AspectJ方式进行事务切入
// 注册类为AnnotationTransactionAspect的BeanDefinition，加载字节码时由AspectJ织入增强
public static final String TRANSACTION_ASPECT_CLASS_NAME =
"org.springframework.transaction.aspectj.AnnotationTransactionAspect";
private void registerTransactionAspect(Element element, ParserContext parserContext) {
String txAspectBeanName = TransactionManagementConfigUtils.TRANSACTION_ASPECT_BEAN_NAME;
String txAspectClassName = TransactionManagementConfigUtils.TRANSACTION_ASPECT_CLASS_NAME;
if (!parserContext.getRegistry().containsBeanDefinition(txAspectBeanName)) {
RootBeanDefinition def = new RootBeanDefinition();
def.setBeanClassName(txAspectClassName);
def.setFactoryMethodName("aspectOf");
registerTransactionManager(element, def);
parserContext.registerBeanComponent(new BeanComponentDefinition(def, txAspectBeanName));
}
}
// 注册类为JtaAnnotationTransactionAspect的BeanDefinition，加载字节码时由AspectJ织入增强
public static final String JTA_TRANSACTION_ASPECT_CLASS_NAME =
"org.springframework.transaction.aspectj.JtaAnnotationTransactionAspect";
private void registerJtaTransactionAspect(Element element, ParserContext parserContext) {
String txAspectBeanName = TransactionManagementConfigUtils.JTA_TRANSACTION_ASPECT_BEAN_NAME;
String txAspectClassName = TransactionManagementConfigUtils.JTA_TRANSACTION_ASPECT_CLASS_NAME;
if (!parserContext.getRegistry().containsBeanDefinition(txAspectBeanName)) {
RootBeanDefinition def = new RootBeanDefinition();
def.setBeanClassName(txAspectClassName);
def.setFactoryMethodName("aspectOf");
registerTransactionManager(element, def);
parserContext.registerBeanComponent(new BeanComponentDefinition(def, txAspectBeanName));
}
}
private static void registerTransactionManager(Element element, BeanDefinition def) {
def.getPropertyValues().add("transactionManagerBeanName",
TxNamespaceHandler.getTransactionManagerName(element));
}
3.3 Spring Aop方式进行事务切入 AopAutoProxyConfigurer
private static class AopAutoProxyConfigurer {
public static void configureAutoProxyCreator(Element element, ParserContext parserContext) {
AopNamespaceUtils.registerAutoProxyCreatorIfNecessary(parserContext, element);
String txAdvisorBeanName = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME;
if (!parserContext.getRegistry().containsBeanDefinition(txAdvisorBeanName)) {
Object eleSource = parserContext.extractSource(element);
// Create the TransactionAttributeSource definition.
RootBeanDefinition sourceDef = new RootBeanDefinition(
"org.springframework.transaction.annotation.AnnotationTransactionAttributeSource");
sourceDef.setSource(eleSource);
sourceDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
String sourceName = parserContext.getReaderContext().registerWithGeneratedName(sourceDef);
// Create the TransactionInterceptor definition.
RootBeanDefinition interceptorDef = new RootBeanDefinition(TransactionInterceptor.class);
interceptorDef.setSource(eleSource);
interceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registerTransactionManager(element, interceptorDef);
interceptorDef.getPropertyValues().add("transactionAttributeSource", new RuntimeBeanReference(sourceName));
String interceptorName = parserContext.getReaderContext().registerWithGeneratedName(interceptorDef);
// Create the TransactionAttributeSourceAdvisor definition.
RootBeanDefinition advisorDef = new RootBeanDefinition(BeanFactoryTransactionAttributeSourceAdvisor.class);
advisorDef.setSource(eleSource);
advisorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
advisorDef.getPropertyValues().add("transactionAttributeSource", new RuntimeBeanReference(sourceName));
advisorDef.getPropertyValues().add("adviceBeanName", interceptorName);
if (element.hasAttribute("order")) {
advisorDef.getPropertyValues().add("order", element.getAttribute("order"));
}
parserContext.getRegistry().registerBeanDefinition(txAdvisorBeanName, advisorDef);
CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), eleSource);
compositeDef.addNestedComponent(new BeanComponentDefinition(sourceDef, sourceName));
compositeDef.addNestedComponent(new BeanComponentDefinition(interceptorDef, interceptorName));
compositeDef.addNestedComponent(new BeanComponentDefinition(advisorDef, txAdvisorBeanName));
parserContext.registerComponent(compositeDef);
}
}
}
3.3.1 注册事务代理自动创建器 InfrastructureAdvisorAutoProxyCreator
3.3.1.1 AopNamespaceUtils.registerAutoProxyCreatorIfNecessary
public static void registerAutoProxyCreatorIfNecessary(
ParserContext parserContext, Element sourceElement) {
BeanDefinition beanDefinition = AopConfigUtils.registerAutoProxyCreatorIfNecessary(
parserContext.getRegistry(), parserContext.extractSource(sourceElement));
// 是否基于类创建代理、是否暴露代理对象
useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
registerComponentIfNecessary(beanDefinition, parserContext);
}
3.3.1.2 AopConfigUtils.registerAutoProxyCreatorIfNecessary
public static BeanDefinition registerAutoProxyCreatorIfNecessary(
BeanDefinitionRegistry registry, @Nullable Object source) {
// 注册代理自动创建器 InfrastructureAdvisorAutoProxyCreator
return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source);
}
3.3.1.3 代理自动创建器 InfrastructureAdvisorAutoProxyCreator
仅考虑 infrastructure Advisor Bean 的自动代理创建者，忽略任何应用程序定义的Advisors。
public class InfrastructureAdvisorAutoProxyCreator extends AbstractAdvisorAutoProxyCreator {
@Nullable
private ConfigurableListableBeanFactory beanFactory;
// 保存beanFactory
@Override
protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.initBeanFactory(beanFactory);
this.beanFactory = beanFactory;
}
// 查找Advisor时判断是否是适用的：只有是系统定义的角色为ROLE_INFRASTRUCTURE才是适用的，用户自定义的等Advisor将被忽略
@Override
protected boolean isEligibleAdvisorBean(String beanName) {
return (this.beanFactory != null && this.beanFactory.containsBeanDefinition(beanName) &&
this.beanFactory.getBeanDefinition(beanName).getRole() == BeanDefinition.ROLE_INFRASTRUCTURE);
}
}
3.3.1.4 查找匹配Bean的Advisor(系统定义的角色为ROLE_INFRASTRUCTURE的Advisor)
在《动态AOP-Spring AOP 基于@AspectJ》一文中已经分析过，代理自动创建者。在其父类AbstractAdvisorAutoProxyCreator方法getAdvicesAndAdvisorsForBean获取匹配当前Bean的AdvicesAndAdvisors时，会判断哪些Advice或Advisor是候选者。
// 查找匹配Bean的AdvicesAndAdvisor
protected Object[] getAdvicesAndAdvisorsForBean(
Class beanClass, String beanName, @Nullable TargetSource targetSource) {
List
if (advisors.isEmpty()) {
return DO_NOT_PROXY;
}
return advisors.toArray();
}
// 查找匹配指定Bean的AdvicesAndAdvisor
protected List
List
// 匹配指定Bean的Advisor，传送门3.3.2.5
List
extendAdvisors(eligibleAdvisors);
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors = sortAdvisors(eligibleAdvisors);
}
return eligibleAdvisors;
}
// 查找所有的Advisor
protected List
Assert.state(this.advisorRetrievalHelper != null, "No BeanFactoryAdvisorRetrievalHelper available");
// 调用的是BeanFactoryAdvisorRetrievalHelperAdapter
return this.advisorRetrievalHelper.findAdvisorBeans();
}
// Advisor查找辅助类
private class BeanFactoryAdvisorRetrievalHelperAdapter extends BeanFactoryAdvisorRetrievalHelper {
public BeanFactoryAdvisorRetrievalHelperAdapter(ConfigurableListableBeanFactory beanFactory) {
super(beanFactory);
}
@Override
protected boolean isEligibleBean(String beanName) {
// 调用了InfrastructureAdvisorAutoProxyCreator.isEligibleAdvisorBean
return AbstractAdvisorAutoProxyCreator.this.isEligibleAdvisorBean(beanName);
}
}
3.3.1.5 过滤匹配Bean的Advisor
protected List
List
ProxyCreationContext.setCurrentProxiedBeanName(beanName);
try {
return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
}
finally {
ProxyCreationContext.setCurrentProxiedBeanName(null);
}
}
AopUtils.findAdvisorsThatCanApply
public static List
if (candidateAdvisors.isEmpty()) {
return candidateAdvisors;
}
List
for (Advisor candidate : candidateAdvisors) {
if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
eligibleAdvisors.add(candidate);
}
}
boolean hasIntroductions = !eligibleAdvisors.isEmpty();
// 包含解析自定义事物标签时注入的BeanFactoryTransactionAttributeSourceAdvisor
for (Advisor candidate : candidateAdvisors) {
if (candidate instanceof IntroductionAdvisor) {
// already processed
continue;
}
if (canApply(candidate, clazz, hasIntroductions)) {
eligibleAdvisors.add(candidate);
}
}
return eligibleAdvisors;
}
AopUtils.canApply
public static boolean canApply(Advisor advisor, Class targetClass) {
return canApply(advisor, targetClass, false);
}
public static boolean canApply(Advisor advisor, Class targetClass, boolean hasIntroductions) {
if (advisor instanceof IntroductionAdvisor) {
return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
}
else if (advisor instanceof PointcutAdvisor) {
PointcutAdvisor pca = (PointcutAdvisor) advisor;
// pca是解析自定义事物标签时注入的BeanFactoryTransactionAttributeSourceAdvisor，Pointcut就是其内部的TransactionAttributeSourcePointcut
return canApply(pca.getPointcut(), targetClass, hasIntroductions);
}
else {
// It doesn't have a pointcut so we assume it applies.
return true;
}
}
public static boolean canApply(Pointcut pc, Class targetClass, boolean hasIntroductions) {
Assert.notNull(pc, "Pointcut must not be null");
if (!pc.getClassFilter().matches(targetClass)) {
return false;
}
// pc是BeanFactoryTransactionAttributeSourceAdvisor属性TransactionAttributeSourcePointcut，TransactionAttributeSourcePointcut用到了注入的TransactionAttributeSource
MethodMatcher methodMatcher = pc.getMethodMatcher();
if (methodMatcher == MethodMatcher.TRUE) {
// No need to iterate the methods if we're matching any method anyway...
return true;
}
IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null;
if (methodMatcher instanceof IntroductionAwareMethodMatcher) {
introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher;
}
Set
if (!Proxy.isProxyClass(targetClass)) {
classes.add(ClassUtils.getUserClass(targetClass));
}
classes.addAll(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
for (Class clazz : classes) {
Method[] methods = ReflectionUtils.getAllDeclaredMethods(clazz);
for (Method method : methods) {
if (introductionAwareMethodMatcher != null ?
introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions) :
methodMatcher.matches(method, targetClass)) {
return true;
}
}
}
return false;
}
3.3.2 基于事务注解获取事务属性 AnnotationTransactionAttributeSource
读取Spring的JDK 1.5+ {@link Transactional}注解，封装成TransactionAttribute，并将相应的事务属性公开给Spring的事务基础结构。 还支持JTA 1.2的{@link javax.transaction.Transactional}和EJB3的{@link javax.ejb.TransactionAttribute}注解（如果存在）。 也可以用作自定义TransactionAttributeSource的基类，或通过{@link TransactionAnnotationParser}策略进行自定义。
3.3.2.1 置入TransactionAnnotationParser AnnotationTransactionAttributeSource
static {
ClassLoader classLoader = AnnotationTransactionAttributeSource.class.getClassLoader();
jta12Present = ClassUtils.isPresent("javax.transaction.Transactional", classLoader);
ejb3Present = ClassUtils.isPresent("javax.ejb.TransactionAttribute", classLoader);
}
public AnnotationTransactionAttributeSource() {
this(true);
}
public AnnotationTransactionAttributeSource(boolean publicMethodsOnly) {
this.publicMethodsOnly = publicMethodsOnly;
if (jta12Present || ejb3Present) {
this.annotationParsers = new LinkedHashSet<>(4);
this.annotationParsers.add(new SpringTransactionAnnotationParser());
if (jta12Present) {
this.annotationParsers.add(new JtaTransactionAnnotationParser());
}
if (ejb3Present) {
this.annotationParsers.add(new Ejb3TransactionAnnotationParser());
}
}
else {
this.annotationParsers = Collections.singleton(new SpringTransactionAnnotationParser());
}
}
3.3.2.2 获取事务属性 AbstractFallbackTransactionAttributeSource.getTransactionAttribute
// 获取指定方法调用的事务属性。如果未找到方法属性，则默认为方法所属类的事务属性。
public TransactionAttribute getTransactionAttribute(Method method, @Nullable Class targetClass) {
if (method.getDeclaringClass() == Object.class) {
return null;
}
// First, see if we have a cached value.
Object cacheKey = getCacheKey(method, targetClass);
TransactionAttribute cached = this.attributeCache.get(cacheKey);
if (cached != null) {
// Value will either be canonical value indicating there is no transaction attribute,
// or an actual transaction attribute.
if (cached == NULL_TRANSACTION_ATTRIBUTE) {
return null;
}
else {
return cached;
}
}
else {
// 查找指定方法的TransactionAttribute，不一定是方法上的注解
TransactionAttribute txAttr = computeTransactionAttribute(method, targetClass);
// Put it in the cache.
if (txAttr == null) {
this.attributeCache.put(cacheKey, NULL_TRANSACTION_ATTRIBUTE);
}
else {
// 返回给定方法的完全限定名称，包括完全限定的接口/类名称+“.” +方法名称。
String methodIdentification = ClassUtils.getQualifiedMethodName(method, targetClass);
if (txAttr instanceof DefaultTransactionAttribute) {
((DefaultTransactionAttribute) txAttr).setDescriptor(methodIdentification);
}
if (logger.isTraceEnabled()) {
logger.trace("Adding transactional method '" + methodIdentification + "' with attribute: " + txAttr);
}
this.attributeCache.put(cacheKey, txAttr);
}
return txAttr;
}
}
3.3.2.3 查找事务属性 AbstractFallbackTransactionAttributeSource.computeTransactionAttribute
对于事务属性获取规则：如果方法中存在事务属性，则使用方法上的事物属性，否则使用方法所在的类上的属性；如果方法所在类的属性上还是没有搜寻到对应的事务属性，那么再搜寻接口中的方法，再没有的话，最后尝试搜寻接口的类上面的声明。
// 查找指定方法的TransactionAttribute，不一定是方法上的注解
protected TransactionAttribute computeTransactionAttribute(Method method, @Nullable Class targetClass) {
// 禁止非Public方法获取TransactionAttribute。
if (allowPublicMethodsOnly() && !Modifier.isPublic(method.getModifiers())) {
return null;
}
//该方法可能在接口上，但是我们需要目标类的属性。 如果目标类为null，则该方法将保持不变。method接口中的方法，specificMethod实现类中的方法。
Method specificMethod = AopUtils.getMostSpecificMethod(method, targetClass);
// 实现类方法中是否存在事务声明
TransactionAttribute txAttr = findTransactionAttribute(specificMethod);
if (txAttr != null) {
return txAttr;
}
// 实现类是否存在事务声明
txAttr = findTransactionAttribute(specificMethod.getDeclaringClass());
if (txAttr != null && ClassUtils.isUserLevelMethod(method)) {
return txAttr;
}
// 方法是接口定义的
if (specificMethod != method) {
// 接口的方法中是否存在事务声明
txAttr = findTransactionAttribute(method);
if (txAttr != null) {
return txAttr;
}
// 接口是否存在事务声明
txAttr = findTransactionAttribute(method.getDeclaringClass());
if (txAttr != null && ClassUtils.isUserLevelMethod(method)) {
return txAttr;
}
}
return null;
}
3.3.2.4 查找事务属性 AnnotationTransactionAttributeSource.findTransactionAttribute
protected TransactionAttribute findTransactionAttribute(Class clazz) {
return determineTransactionAttribute(clazz);
}
@Override
@Nullable
protected TransactionAttribute findTransactionAttribute(Method method) {
return determineTransactionAttribute(method);
}
// 确定给定方法或类的事务属性。 此实现委派了已配置的{@link TransactionAnnotationParser SpringTransactionAnnotationParsers} ，用于将已知的注释解析为Spring的元数据属性类。 如果不是事务型，则返回{@code null}。
@Nullable
protected TransactionAttribute determineTransactionAttribute(AnnotatedElement element) {
// AnnotationTransactionAttributeSource实例化时往this.annotationParsers中默认加入了SpringTransactionAnnotationParser
for (TransactionAnnotationParser annotationParser : this.annotationParsers) {
TransactionAttribute attr = annotationParser.parseTransactionAnnotation(element);
if (attr != null) {
return attr;
}
}
return null;
}
3.3.3 事务拦截器 TransactionInterceptor
3.3.3.1 执行调用 invokeWithinTransaction
public Object invoke(MethodInvocation invocation) throws Throwable {
// 可能是{@code null}，transactionAttributeSource应该传递给目标类以及方法（可能来自接口）。
Class targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
// Adapt to TransactionAspectSupport's invokeWithinTransaction...
return invokeWithinTransaction(invocation.getMethod(), targetClass, invocation::proceed);
}
(1) 通过TransactionAttributeSource获取TransactionAttribute
(2) 获取PlatformTransactionManager
(3) 生成方法唯一标识
(4) 判断是声明式事务还是编程式事务
声明式事务：
创建TransactionInfo并绑定到当前线程
执行被增强方法
如果执行异常则走异常处理分支
清楚事务信息
提交事务
编程式事务：
创建TransactionInfo并绑定到当前线程
执行被增强方法
清楚事务信息
TransactionAspectSupport
protected Object invokeWithinTransaction(Method method, @Nullable Class targetClass,
final InvocationCallback invocation) throws Throwable {
// 如果事物属性为null，则该方法为非事务处理
TransactionAttributeSource tas = getTransactionAttributeSource();
final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);
// 获取事务管理器
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
// 生成方法唯一表示
final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);
// 声明式事物
if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
// 创建新的TransactionInfo并绑定到当前线程
TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
Object retVal;
try {
// 环绕增强：拦截器链中的下一个拦截器，通常，这将导致目标对象被调用。
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// 处理异常：提交或回滚
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
// 清空事务信息
cleanupTransactionInfo(txInfo);
}
// 提交事务
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
// 编程式事务 创建异常持有者
final ThrowableHolder throwableHolder = new ThrowableHolder();
// 这是一个CallbackPreferringPlatformTransactionManager：传入一个TransactionCallback。
try {
Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr, status -> {
// 创建事务信息
TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
try {
return invocation.proceedWithInvocation();
}
catch (Throwable ex) {
if (txAttr.rollbackOn(ex)) {
// RuntimeException：将导致回滚。
if (ex instanceof RuntimeException) {
throw (RuntimeException) ex;
}
else {
throw new ThrowableHolderException(ex);
}
}
else {
// 正常的返回值：将导致提交。
throwableHolder.throwable = ex;
return null;
}
}
finally {
// 清空事务信息
cleanupTransactionInfo(txInfo);
}
});
// 检查结果状态：它可能指示要抛出的Throwable。
if (throwableHolder.throwable != null) {
throw throwableHolder.throwable;
}
return result;
}
catch (ThrowableHolderException ex) {
throw ex.getCause();
}
catch (TransactionSystemException ex2) {
// 应用程序异常被提交异常覆盖
if (throwableHolder.throwable != null) {
logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
ex2.initApplicationException(throwableHolder.throwable);
}
throw ex2;
}
catch (Throwable ex2) {
// 应用程序异常被提交异常覆盖
if (throwableHolder.throwable != null) {
logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
}
throw ex2;
}
}
}
3.3.3.2 获取事物管理器 determineTransactionManager
获取事物管理器流程
(1) 如果未设置事物属性，直接返回TransactionAspectSupport.transactionManager
(2) 事物属性存在qualifier或TransactionAspectSupport.transactionManagerBeanName存在，获取指定的事务管理器
(3) 不获取指定的事务管理器，直接返回TransactionAspectSupport.transactionManager，不存在从缓存中获取
(4) 如果缓存中不存在则从容器中获取类型为PlatformTransactionManager的Bean
protected PlatformTransactionManager determineTransactionManager(@Nullable TransactionAttribute txAttr) {
// 如果未设置事物属性，请勿尝试查找事物管理器，返回TransactionAspectSupport.transactionManager
if (txAttr == null || this.beanFactory == null) {
return getTransactionManager();
}
String qualifier = txAttr.getQualifier();
if (StringUtils.hasText(qualifier)) {
// 获取qualifier指定的事务管理器
return determineQualifiedTransactionManager(this.beanFactory, qualifier);
}
else if (StringUtils.hasText(this.transactionManagerBeanName)) {
// 获取this.transactionManagerBeanName指定的事务管理器
return determineQualifiedTransactionManager(this.beanFactory, this.transactionManagerBeanName);
}
else {
// 返回TransactionAspectSupport.transactionManager
PlatformTransactionManager defaultTransactionManager = getTransactionManager();
if (defaultTransactionManager == null) {
// 从缓存中获取，如果不存在则从容器中获取类型为PlatformTransactionManager的Bean
defaultTransactionManager = this.transactionManagerCache.get(DEFAULT_TRANSACTION_MANAGER_KEY);
if (defaultTransactionManager == null) {
defaultTransactionManager = this.beanFactory.getBean(PlatformTransactionManager.class);
this.transactionManagerCache.putIfAbsent(
DEFAULT_TRANSACTION_MANAGER_KEY, defaultTransactionManager);
}
}
return defaultTransactionManager;
}
}
// 获取指定名称的事务管理器并缓存起来
private PlatformTransactionManager determineQualifiedTransactionManager(BeanFactory beanFactory, String qualifier) {
PlatformTransactionManager txManager = this.transactionManagerCache.get(qualifier);
if (txManager == null) {
txManager = BeanFactoryAnnotationUtils.qualifiedBeanOfType(
beanFactory, PlatformTransactionManager.class, qualifier);
this.transactionManagerCache.putIfAbsent(qualifier, txManager);
}
return txManager;
}
3.3.3.3 生成方法唯一标识 methodIdentification
private String methodIdentification(Method method, @Nullable Class targetClass,
@Nullable TransactionAttribute txAttr) {
String methodIdentification = methodIdentification(method, targetClass);
if (methodIdentification == null) {
if (txAttr instanceof DefaultTransactionAttribute) {
methodIdentification = ((DefaultTransactionAttribute) txAttr).getDescriptor();
}
if (methodIdentification == null) {
methodIdentification = ClassUtils.getQualifiedMethodName(method, targetClass);
}
}
return methodIdentification;
}
@Nullable
protected String methodIdentification(Method method, @Nullable Class targetClass) {
return null;
}
3.3.3.4 创建事务信息 createTransactionIfNecessary
protected TransactionInfo createTransactionIfNecessary(@Nullable PlatformTransactionManager tm,
@Nullable TransactionAttribute txAttr, final String joinpointIdentification) {
// 如果未指定事务名称，则将方法标识用作事务名称。
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) {
// 根据事务属性中指定的传播行为，返回当前活动的事务或创建新的事务。
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);
}
3.3.3.5 创建事务信息 TransactionInfo
// 为给定的事务属性和状态对象创建一个TransactionInfo，事务属性(txAttr)是否为NULL决定方法是否是事务性
protected TransactionInfo prepareTransactionInfo(@Nullable PlatformTransactionManager tm,
@Nullable TransactionAttribute txAttr, String joinpointIdentification,
@Nullable TransactionStatus status) {
TransactionInfo txInfo = new TransactionInfo(tm, txAttr, joinpointIdentification);
if (txAttr != null) {
// 方法需要事务
if (logger.isTraceEnabled()) {
logger.trace("Getting transaction for [" + txInfo.getJoinpointIdentification() + "]");
}
// 如果已经存在不兼容的事务，事务管理器将标记错误。TransactionInfo.hasTransaction()方法将返回true。《Spring5.X 事务管理器 PlatformTransactionManager》
txInfo.newTransactionStatus(status);
}
else {
// 方法不需要事务，TransactionInfo.hasTransaction()方法将返回false。我们仅创建它以保持此类中维护的ThreadLocal堆栈的完整性。
if (logger.isTraceEnabled()) {
logger.trace("No need to create transaction for [" + joinpointIdentification +
"]: This method is not transactional.");
}
}
// 我们始终将TransactionInfo绑定到线程，即使我们没有在此处创建新的事务。这保证即使此方面未创建任何事务，也将正确管理TransactionInfo堆栈
txInfo.bindToThread();
return txInfo;
}
3.3.3.6 异常处理 completeTransactionAfterThrowing
protected void completeTransactionAfterThrowing(@Nullable TransactionInfo txInfo, Throwable ex) {
// 事务信息存在事务状态(根据事务属性从事务管理器中获取的，传送门3.3.4.4)
if (txInfo != null && txInfo.getTransactionStatus() != null) {
if (logger.isTraceEnabled()) {
logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
"] after exception: " + ex);
}
// 当前异常是执行事务回滚的异常
if (txInfo.transactionAttribute != null && txInfo.transactionAttribute.rollbackOn(ex)) {
try {
txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
}
catch (TransactionSystemException ex2) {
logger.error("Application exception overridden by rollback exception", ex);
ex2.initApplicationException(ex);
throw ex2;
}
catch (RuntimeException | Error ex2) {
logger.error("Application exception overridden by rollback exception", ex);
throw ex2;
}
}
else {
// 如果TransactionStatus.isRollbackOnly（）为true，仍将回滚。
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 | Error ex2) {
logger.error("Application exception overridden by commit exception", ex);
throw ex2;
}
}
}
}
3.3.3.7 清除事务信息 cleanupTransactionInfo
protected void cleanupTransactionInfo(@Nullable TransactionInfo txInfo) {
if (txInfo != null) {
// 调用TransactionInfo.restoreThreadLocalStatus
txInfo.restoreThreadLocalStatus();
}
}
TransactionInfo
private void bindToThread() {
// 公开当前的TransactionStatus，并保留所有现有的TransactionStatus，以便在此事务完成后进行恢复。
this.oldTransactionInfo = transactionInfoHolder.get();
transactionInfoHolder.set(this);
}
private void restoreThreadLocalStatus() {
// 使用堆栈还原旧的事务TransactionInfo。 如果未设置，则为null。
transactionInfoHolder.set(this.oldTransactionInfo);
}
3.3.3.8 提交事务 commitTransactionAfterReturning
// 在成功完成调用之后执行，但是在处理异常之后不执行。 如果我们不创建事务，则不执行任何操作。
protected void commitTransactionAfterReturning(@Nullable TransactionInfo txInfo) {
if (txInfo != null && txInfo.getTransactionStatus() != null) {
if (logger.isTraceEnabled()) {
logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() + "]");
}
txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
}
}
3.3.4 注册类型为BeanFactoryTransactionAttributeSourceAdvisor的Bean
3.3.4.1 BeanFactoryTransactionAttributeSourceAdvisor
public class BeanFactoryTransactionAttributeSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {
@Nullable
private TransactionAttributeSource transactionAttributeSource;
private final TransactionAttributeSourcePointcut pointcut = new TransactionAttributeSourcePointcut() {
@Override
@Nullable
protected TransactionAttributeSource getTransactionAttributeSource() {
return transactionAttributeSource;
}
};
}
3.3.4.2 TransactionAttributeSourcePointcut
abstract class TransactionAttributeSourcePointcut extends StaticMethodMatcherPointcut implements Serializable {
@Override
public boolean matches(Method method, Class targetClass) {
if (TransactionalProxy.class.isAssignableFrom(targetClass) ||
PlatformTransactionManager.class.isAssignableFrom(targetClass) ||
PersistenceExceptionTranslator.class.isAssignableFrom(targetClass)) {
return false;
}
TransactionAttributeSource tas = getTransactionAttributeSource();
// 传送门 3.3.3.1
return (tas == null || tas.getTransactionAttribute(method, targetClass) != null);
}
// 获取基础的TransactionAttributeSource（可以为{@code null}）。 由子类实现。
@Nullable
protected abstract TransactionAttributeSource getTransactionAttributeSource();
}