一、使用
1.maven 依赖
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.2</version>
<relativePath/>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.29</version>
</dependency>
</dependencies>2.配置文件
application.yml 配置数据源
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/temp
username: root
password: 1234563.java
业务类：
public interface IndexService {
void insert(Integer id, String name);
}@Service
public class IndexServiceImpl implements IndexService {
@Autowired
private JdbcTemplate jdbcTemplate;
@Transactional
@Override
public void insert(Integer id, String name) {
jdbcTemplate.execute(String.format("INSERT INTO student_tbl VALUES(%s, '%s')", id, name));
throw new RuntimeException();
}
}调用：
@Component
public class MyApplicationRunner implements ApplicationRunner {
@Autowired
private IndexService studentService;
@Override
public void run(ApplicationArguments args) {
try {
studentService.insert(1, "zhang1");
} catch (Exception e) {
// ignore
}
}
}启动类：
@SpringBootApplication(proxyBeanMethods = false)
public class Boot {
public static void main(String[] args) {
SpringApplication.run(Boot.class, args);
}
}二、原理
1.加载 TransactionAutoConfiguration
spring-boot-autoconfigure-2.7.2.jar 下有文件
org.springframework.boot.autoconfigure.AutoConfiguration.imports，内有：
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration2.加载 TransactionManagementConfigurationSelector
则 springboot 会加载 TransactionAutoConfiguration，根据其，会加载 @EnableTransactionManagement，后加载，后加载 TransactionManagementConfigurationSelector
// TransactionAutoConfiguration.java
@AutoConfiguration(after = { JtaAutoConfiguration.class, HibernateJpaAutoConfiguration.class,
DataSourceTransactionManagerAutoConfiguration.class, Neo4jDataAutoConfiguration.class })
@ConditionalOnClass(PlatformTransactionManager.class)
@EnableConfigurationProperties(TransactionProperties.class)
public class TransactionAutoConfiguration {
...
@Configuration(proxyBeanMethods = false)
@ConditionalOnBean(TransactionManager.class)
@ConditionalOnMissingBean(AbstractTransactionManagementConfiguration.class)
public static class EnableTransactionManagementConfiguration {
@Configuration(proxyBeanMethods = false)
@EnableTransactionManagement(proxyTargetClass = false)
@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false")
public static class JdkDynamicAutoProxyConfiguration {
}
@Configuration(proxyBeanMethods = false)
@EnableTransactionManagement(proxyTargetClass = true)
@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true",
matchIfMissing = true)
public static class CglibAutoProxyConfiguration {
}
}
}// EnableTransactionManagement.java
@Import(TransactionManagementConfigurationSelector.class)
public @interface EnableTransactionManagement {
}3.加载 InfrastructureAdvisorAutoProxyCreator 和 BeanFactoryTransactionAttributeSourceAdvisor
TransactionManagementConfigurationSelector 注入 AutoProxyRegistrar 和 ProxyTransactionManagementConfiguration
注意：如果依赖包含 AOP，会根据 AopAutoConfiguration，加载 @EnableAspectJAutoProxy，会注册 AnnotationAwareAspectJAutoProxyCreator，就不会注册 InfrastructureAdvisorAutoProxyCreator
// TransactionManagementConfigurationSelector.java
@Override
protected String[] selectImports(AdviceMode adviceMode) {
switch (adviceMode) {
case PROXY:
return new String[] {AutoProxyRegistrar.class.getName(),
ProxyTransactionManagementConfiguration.class.getName()};
case ASPECTJ:
return new String[] {determineTransactionAspectClass()};
default:
return null;
}
}// AutoProxyRegistrar.java
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
boolean candidateFound = false;
Set<String> annTypes = importingClassMetadata.getAnnotationTypes();
for (String annType : annTypes) {
AnnotationAttributes candidate = AnnotationConfigUtils.attributesFor(importingClassMetadata, annType);
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;
if (mode == AdviceMode.PROXY) {
AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry);
if ((Boolean) proxyTargetClass) {
AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
return;
}
}
}
}
...
}调用 AopConfigUtils 注册 InfrastructureAdvisorAutoProxyCreator
// AopConfigUtils.java
public static final String AUTO_PROXY_CREATOR_BEAN_NAME =
"org.springframework.aop.config.internalAutoProxyCreator";
@Nullable
public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
return registerAutoProxyCreatorIfNecessary(registry, null);
}
@Nullable
public static BeanDefinition registerAutoProxyCreatorIfNecessary(
BeanDefinitionRegistry registry, @Nullable Object source) {
return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source);
}
public static void forceAutoProxyCreatorToExposeProxy(BeanDefinitionRegistry registry) {
if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
definition.getPropertyValues().add("exposeProxy", Boolean.TRUE);
}
}ProxyTransactionManagementConfiguration 会注册 BeanFactoryTransactionAttributeSourceAdvisor
// ProxyTransactionManagementConfiguration.java
@Configuration(proxyBeanMethods = false)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration {
@Bean(name = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor(
TransactionAttributeSource transactionAttributeSource, TransactionInterceptor transactionInterceptor) {
BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor();
advisor.setTransactionAttributeSource(transactionAttributeSource);
advisor.setAdvice(transactionInterceptor);
if (this.enableTx != null) {
advisor.setOrder(this.enableTx.<Integer>getNumber("order"));
}
return advisor;
}
...
}4.创建代理类 AopProxy
所有的 bean 会执行 InfrastructureAdvisorAutoProxyCreator 的 postProcessBeforeInstantiation 方法
// AbstractAutoProxyCreator.java
@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
if (bean != null) {
Object cacheKey = getCacheKey(bean.getClass(), beanName);
if (this.earlyProxyReferences.remove(cacheKey) != bean) {
return wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// Create proxy if we have advice.
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
this.advisedBeans.put(cacheKey, Boolean.TRUE);
Object proxy = createProxy(
bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
protected Object createProxy(Class<?> beanClass, @Nullable String beanName,
@Nullable Object[] specificInterceptors, TargetSource targetSource) {
...
ProxyFactory proxyFactory = new ProxyFactory();
proxyFactory.copyFrom(this);
if (proxyFactory.isProxyTargetClass()) {
// Explicit handling of JDK proxy targets and lambdas (for introduction advice scenarios)
if (Proxy.isProxyClass(beanClass) || ClassUtils.isLambdaClass(beanClass)) {
// Must allow for introductions; can't just set interfaces to the proxy's interfaces only.
for (Class<?> ifc : beanClass.getInterfaces()) {
proxyFactory.addInterface(ifc);
}
}
}
else {
// No proxyTargetClass flag enforced, let's apply our default checks...
if (shouldProxyTargetClass(beanClass, beanName)) {
proxyFactory.setProxyTargetClass(true);
}
else {
evaluateProxyInterfaces(beanClass, proxyFactory);
}
}
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
proxyFactory.addAdvisors(advisors);
....
return proxyFactory.getProxy(classLoader);
}findCandidateAdvisors() 会查找到 BeanFactoryTransactionAttributeSourceAdvisor
findAdvisorsThatCanApply() 查找匹配的 Advisor，其中会使用 SpringTransactionAnnotationParser 解析方法是否有 @Transactional
// AbstractAdvisorAutoProxyCreator.java
@Override
@Nullable
protected Object[] getAdvicesAndAdvisorsForBean(
Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
if (advisors.isEmpty()) {
return DO_NOT_PROXY;
}
return advisors.toArray();
}
protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
List<Advisor> candidateAdvisors = findCandidateAdvisors();
List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
extendAdvisors(eligibleAdvisors);
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors = sortAdvisors(eligibleAdvisors);
}
return eligibleAdvisors;
}ProxyFactory 创建代理类
// ProxyFactory.java
public Object getProxy(@Nullable ClassLoader classLoader) {
return createAopProxy().getProxy(classLoader);
}// ProxyCreatorSupport.java
protected final synchronized AopProxy createAopProxy() {
if (!this.active) {
activate();
}
return getAopProxyFactory().createAopProxy(this);
}// DefaultAopProxyFactory.java
@Override
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
if (!NativeDetector.inNativeImage() &&
(config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config))) {
Class<?> targetClass = config.getTargetClass();
if (targetClass == null) {
throw new AopConfigException("TargetSource cannot determine target class: " +
"Either an interface or a target is required for proxy creation.");
}
if (targetClass.isInterface() || Proxy.isProxyClass(targetClass) || ClassUtils.isLambdaClass(targetClass)) {
return new JdkDynamicAopProxy(config);
}
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}5.创建代理类
默认会创建 Cglib 的 AopProxy，可在 application.yml 中配置 spring.aop.proxy-target-class = false，创建 Jdk 的 AopProxy
spring:
aop:
proxy-target-class: false5.1 创建 cglib 代理类
创建 cglib 代理类，创建了 7 个 Callback：
- CglibAopProxy$DynamicAdvisedInterceptor
- CglibAopProxy$StaticUnadvisedInterceptor
- CglibAopProxy$SerializableNoOp
- CglibAopProxy$StaticDispatcher
- CglibAopProxy$AdvisedDispatcher
- CglibAopProxy$EqualsInterceptor
- CglibAopProxy$HashCodeInterceptor
通过 ProxyCallbackFilter 的 accept() 方法，决定不同的方法走不同的 Callback
// CglibAopProxy.java
@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
try {
...
Enhancer enhancer = createEnhancer();
...
enhancer.setSuperclass(proxySuperClass);
enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));
enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(classLoader));
Callback[] callbacks = getCallbacks(rootClass);
Class<?>[] types = new Class<?>[callbacks.length];
for (int x = 0; x < types.length; x++) {
types[x] = callbacks[x].getClass();
}
// fixedInterceptorMap only populated at this point, after getCallbacks call above
enhancer.setCallbackFilter(new ProxyCallbackFilter(
this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
enhancer.setCallbackTypes(types);
// Generate the proxy class and create a proxy instance.
return createProxyClassAndInstance(enhancer, callbacks);
}
...
}
private Callback[] getCallbacks(Class<?> rootClass) throws Exception {
boolean exposeProxy = this.advised.isExposeProxy();
boolean isFrozen = this.advised.isFrozen();
boolean isStatic = this.advised.getTargetSource().isStatic();
Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised);
Callback targetInterceptor;
if (exposeProxy) {
targetInterceptor = (isStatic ?
new StaticUnadvisedExposedInterceptor(this.advised.getTargetSource().getTarget()) :
new DynamicUnadvisedExposedInterceptor(this.advised.getTargetSource()));
}
else {
targetInterceptor = (isStatic ?
new StaticUnadvisedInterceptor(this.advised.getTargetSource().getTarget()) :
new DynamicUnadvisedInterceptor(this.advised.getTargetSource()));
}
Callback targetDispatcher = (isStatic ?
new StaticDispatcher(this.advised.getTargetSource().getTarget()) : new SerializableNoOp());
Callback[] mainCallbacks = new Callback[] {
aopInterceptor, // for normal advice
targetInterceptor, // invoke target without considering advice, if optimized
new SerializableNoOp(), // no override for methods mapped to this
targetDispatcher, this.advisedDispatcher,
new EqualsInterceptor(this.advised),
new HashCodeInterceptor(this.advised)
};
Callback[] callbacks;
if (isStatic && isFrozen) {
...
}
else {
callbacks = mainCallbacks;
}
return callbacks;
}5.2 执行 cglib 代理方法
当执行被代理的方法时，会走 Callback 为 CglibAopProxy$DynamicAdvisedInterceptor
执行 this.advised.getInterceptorsAndDynamicInterceptionAdvice 时，把符合的方法转化为执行链，如 @Transactional 转化为 TransactionInterceptor
这里用到过滤器链设计模式，实现多层代理
// CglibAopProxy$DynamicAdvisedInterceptor.java
@Override
@Nullable
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
try {
...
Class<?> targetClass = (target != null ? target.getClass() : null);
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
Object retVal;
if (chain.isEmpty() && CglibMethodInvocation.isMethodProxyCompatible(method)) {
Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
retVal = invokeMethod(target, method, argsToUse, methodProxy);
}
else {
retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();
}
retVal = processReturnType(proxy, target, method, retVal);
return retVal;
}
...
}// CglibMethodInvocation.java
@Override
@Nullable
public Object proceed() throws Throwable {
try {
return super.proceed();
}
...
}// ReflectiveMethodInvocation.java
@Override
@Nullable
public Object proceed() throws Throwable {
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
return invokeJoinpoint();
}
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
...
}
else {
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
}
@Nullable
protected Object invokeJoinpoint() throws Throwable {
return AopUtils.invokeJoinpointUsingReflection(this.target, this.method, this.arguments);
}调用 DataSourceTransactionManager 进行开始事务，提交事务，回滚事务
DataSourceTransactionManager.getTransaction(TransactionDefinition definition) 开启事务
// TransactionInterceptor.java
@Override
@Nullable
public Object invoke(MethodInvocation invocation) throws Throwable {
Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
return invokeWithinTransaction(invocation.getMethod(), targetClass, new CoroutinesInvocationCallback() {
@Override
@Nullable
public Object proceedWithInvocation() throws Throwable {
return invocation.proceed();
}
@Override
public Object getTarget() {
return invocation.getThis();
}
@Override
public Object[] getArguments() {
return invocation.getArguments();
}
});
}
@Nullable
protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targetClass,
final InvocationCallback invocation) throws Throwable {
// If the transaction attribute is null, the method is non-transactional.
TransactionAttributeSource tas = getTransactionAttributeSource();
final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);
final TransactionManager tm = determineTransactionManager(txAttr);
if (this.reactiveAdapterRegistry != null && tm instanceof ReactiveTransactionManager) {
...
return result;
}
PlatformTransactionManager ptm = asPlatformTransactionManager(tm);
final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);
if (txAttr == null || !(ptm instanceof CallbackPreferringPlatformTransactionManager)) {
TransactionInfo txInfo = createTransactionIfNecessary(ptm, txAttr, joinpointIdentification);
Object retVal;
try {
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// target invocation exception
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
cleanupTransactionInfo(txInfo);
}
...
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
...
}
}
protected TransactionInfo createTransactionIfNecessary(@Nullable PlatformTransactionManager tm,
@Nullable TransactionAttribute txAttr, final String joinpointIdentification) {
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) {
status = tm.getTransaction(txAttr);
}
...
}
return prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
}
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());
}
}