SpringBoot+Shiro引起事务失效、错误原因、解决方法

一、问题
今天发现用户注册的Service的事务并没有起到作用,再抛出一个RuntimeException后,并没有发生回滚,下面是调试步骤:

1、检查数据库的引擎是否是innoDB

2、启动类上是否加入@EnableTransactionManagement注解

3、是否在方法上加入@Transactional注解或Service的类上是否有@Transactional注解

4、方法是否为public

5、是否是因为抛出了Exception等checked异常

然而事务失效都不是这些原因引起的,并且发现其他Service的事务都可以正常使用。在查看打印的异常调用链的时候,发现这个Service是没有被AOP代理过的,所以推测可能是因为其他整合Spring的框架提前引用了这个Service。

为了验证,新建了一个Service,并且把代码copy到新建的类中,测试其事务,发现事务可以正常使用,下面是打印的异常信息:

从上面可以明显看到,Spring为这个service生成了代理类,证明事务是可以正常使用的,并且原service的失效应该是其他的整合Spring的框架提前引用造成的。

因为项目还使用了Shiro作为权限管理,并且在编写Shiro的自定义验证器Realm中引用了该UserService,后来把Realm中的Service换成了Mapper后,该Service的事务可以正常使用了。

错误原因:
Spring中事务是通过AOP创建代理对象来完成的,有BeanFactoryTransactionAttributeSourceAdvisor完成对需要事务的方法织入对事务的处理。完成创建AOP代理对象的功能由一个特殊的BeanPostProcessor完成--AnnotationAwareAspectJAutoProxyCreator。该类实现了BeanPostProcessor接口,在bean创建完成并将属性设置好之后,拦截bean,并创建代理对象,在原对象的方法功能上添加增强器中增强方法的处理。对于事务增强器BeanFactoryTransactionAttributeSourceAdvisor而言,也就是在原有方法上加入事务的功能。

但是,在ApplicationContext刷新上下文过程(refresh)中,上下文会调用registerBeanPostProcessors方法将BeanFactory中的所有BeanPostProcessor后处理器注册到BeanFactory中,使其后面流程中创建bean的时候生效。下面是其实现源码:

public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}

// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

// AnnotationAwareAspectJAutoProxyCreator实现了Ordered接口,所以会在这里排序
// 但是,实现Ordered接口的BeanPostProcessor中,有一个是MethodValidationPostProcessor
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);

// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);

// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
上面流程为:

实例化所有实现了PriorityOrdered接口的BeanPostProcessor,排序后注册到BeanFactory
实例化所有实现了Ordered接口的BeanPostProcessor,排序后注册到BeanFactory
实例化剩余的BeanPostProcessor,注册到BeanFactory
注册内部使用的BeanPostProcessor
添加一个特殊的后处理器--ApplicationListenerDetector
由于AnnotationAwareAspectJAutoProxyCreator实现了Ordered接口,所以会在第2步中注册到BeanFactory,然后生效,可以拦截bean创建并生成代理对象。但是,在其注册前,有一个同样实现了Ordered接口的MethodValidationPostProcessor。在该类的实例化过程中,会由ValidationAutoConfiguration通过工厂方法来创建,创建过程中,需要传入Environment对象作为参数,然后Spring会从BeanFactory中查找所有符合Environment类型的bean,下面是查询过程:

//type为需要的参数,类型为Environment
private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
List<String> result = new ArrayList<>();

//遍历BeanFactory中保存的所有beanName
for (String beanName : this.beanDefinitionNames) {
if (!isAlias(beanName)) {
try {
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// 检查是否是合格的bean
if (!mbd.isAbstract() && (allowEagerInit ||
(mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading()) &&
!requiresEagerInitForType(mbd.getFactoryBeanName()))) {
// 是否是FactoryBean.
boolean isFactoryBean = isFactoryBean(beanName, mbd);
BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
boolean matchFound =
(allowEagerInit || !isFactoryBean ||
(dbd != null && !mbd.isLazyInit()) || containsSingleton(beanName)) &&
(includeNonSingletons ||
(dbd != null ? mbd.isSingleton() : isSingleton(beanName))) &&
isTypeMatch(beanName, type);
if (!matchFound && isFactoryBean) {
beanName = FACTORY_BEAN_PREFIX + beanName;
// 如果是FactoryBean,在比较类型是,会实例化FactoryBean对象,用作比对
// isTypeMatch会比较FactoryBean对应的实际类型是否符合,所以会实例化FactoryBean
matchFound = (includeNonSingletons || mbd.isSingleton()) && isTypeMatch(beanName, type);
}
if (matchFound) {
result.add(beanName);
}
}
}
//catch...略
}
}

// Check manually registered singletons too.
//省略直接注册的单例检查

return StringUtils.toStringArray(result);
}
如果存在FactoryBean的话,在比对过程中会实例化FactoryBean(isTypeMatch中实现)

在isTypeMatch中有这么一段代码:

if (FactoryBean.class.isAssignableFrom(beanType)) {
if (!BeanFactoryUtils.isFactoryDereference(name) && beanInstance == null) {
// 如果是FactoryBean类型,需要对其实例化后才能知道到底它创建的bean是什么类型
beanType = getTypeForFactoryBean(beanName, mbd);
if (beanType == null) {
return false;
}
}
}
下面是getTypeForFactoryBean中的创建FactoryBean实例部分的代码:

FactoryBean<?> fb = (mbd.isSingleton() ?
getSingletonFactoryBeanForTypeCheck(beanName, mbd) :
getNonSingletonFactoryBeanForTypeCheck(beanName, mbd));
下面是getSingletonFactoryBeanForTypeCheck实现:

private FactoryBean<?> getSingletonFactoryBeanForTypeCheck(String beanName, RootBeanDefinition mbd) {
synchronized (getSingletonMutex()) {
//先尝试从缓存中获取
BeanWrapper bw = this.factoryBeanInstanceCache.get(beanName);
if (bw != null) {
return (FactoryBean<?>) bw.getWrappedInstance();
}
//从单例缓存中获取
Object beanInstance = getSingleton(beanName, false);
if (beanInstance instanceof FactoryBean) {
return (FactoryBean<?>) beanInstance;
}
if (isSingletonCurrentlyInCreation(beanName) ||
(mbd.getFactoryBeanName() != null && isSingletonCurrentlyInCreation(mbd.getFactoryBeanName()))) {
return null;
}

//创建对象
Object instance;
try {
beforeSingletonCreation(beanName);
instance = resolveBeforeInstantiation(beanName, mbd);
if (instance == null) {
//实例化
bw = createBeanInstance(beanName, mbd, null);
instance = bw.getWrappedInstance();
}
}
finally {
afterSingletonCreation(beanName);
}

FactoryBean<?> fb = getFactoryBean(beanName, instance);
if (bw != null) {
this.factoryBeanInstanceCache.put(beanName, bw);
}
return fb;
}
}
从上面代码看以看到,Spring会实例化FactoryBean,以确定其创建的bean的类型

由于ShiroFilterFactoryBean实现了FactoryBean接口,所以它会提前被初始化。又因为SecurityManager,SecurityManager依赖于Realm实现类、Realm实现类又依赖于UserService,所以引发所有相关的bean提前初始化。

ShiroFilterFactoryBean -> SecurityManager -> Realm实现类 -> UserService

但是此时还只是ApplicationContext中registerBeanPostProcessors注册BeanPostProcessor处理器的阶段,此时AnnotationAwareAspectJAutoProxyCreator还没有注册到BeanFactory中,UserService无法享受到事务处理!

三、解决办法
在Realm实现中使用Mapper,而不是直接使用Service对象。缺点:直接和数据库交互,并且也没有Service中的逻辑交互以及缓存
在Realm中Service声明上加入@Lazy注解,延迟Realm实现中Service对象的初始化时间,这样就可以保证Service实际初始化的时候会被BeanPostProcessor拦截,创建具有事务功能的代理对象

原文:https://blog.csdn.net/finalcola/article/details/81197584

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