http://www.iteye.com/topic/1121357?page=3
基于JDK动态代理和CGLIB动态代理的实现Spring注解管理事务(@Trasactional)到底有什么区别。
我还是喜欢基于Schema风格的Spring事务管理,但也有很多人在用基于@Trasactional注解的事务管理,但在通过基于JDK动态代理和CGLIB动态代理的实现Spring注解管理事务是有区别的,我们接下来看看到底有哪些区别。
一、基础工作
首先修改我们上一次做的 SpringMVC + spring3.1.1 + hibernate4.1.0 集成及常见问题总结,如下所示:
将xml声明式事务删除
- <aop:config expose-proxy="true">
- <!-- 只对业务逻辑层实施事务 -->
- <aop:pointcut id="txPointcut" expression="execution(* cn.javass..service..*.*(..))" />
- <aop:advisor advice-ref="txAdvice" pointcut-ref="txPointcut"/>
- </aop:config>
<aop:config expose-proxy="true"> <!-- 只对业务逻辑层实施事务 --> <aop:pointcut id="txPointcut" expression="execution(* cn.javass..service..*.*(..))" /> <aop:advisor advice-ref="txAdvice" pointcut-ref="txPointcut"/> </aop:config>
并添加注解式事务支持:
- <tx:annotation-driven transaction-manager="txManager"/>
<tx:annotation-driven transaction-manager="txManager"/>
在我们的BaseService接口上添加 @Transactional 使该方法开启事务
- package cn.javass.common.service;
- public interface IBaseService<M extends java.io.Serializable, PK extends java.io.Serializable> {
- @Transactional //开启默认事务
- public int countAll();
- }
package cn.javass.common.service; public interface IBaseService<M extends java.io.Serializable, PK extends java.io.Serializable> { @Transactional //开启默认事务 public int countAll(); }
在我们的log4j.properties中添加如下配置,表示输出spring的所有debug信息
- log4j.logger.org.springframework=INFO,CONSOLE
log4j.logger.org.springframework=INFO,CONSOLE
在我们的resources.properties里将hibernate.show_sql=true 改为true,为了看到hibernate的sql。
单元测试类:
- package cn.javass.ssonline.spider.service.impl;
- import org.junit.Test;
- import org.junit.runner.RunWith;
- import org.springframework.beans.factory.annotation.Autowired;
- import org.springframework.test.context.ContextConfiguration;
- import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
- import org.springframework.test.context.transaction.TransactionConfiguration;
- import cn.javass.demo.service.UserService;
- @RunWith(SpringJUnit4ClassRunner.class)
- @ContextConfiguration(locations = {"classpath:spring-config.xml"})
- public class UserServiceTest2 {
- @Autowired
- private UserService userService;
- @Test
- public void testCreate() {
- userService.countAll();
- }
- }
package cn.javass.ssonline.spider.service.impl; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.test.context.transaction.TransactionConfiguration; import cn.javass.demo.service.UserService; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = {"classpath:spring-config.xml"}) public class UserServiceTest2 { @Autowired private UserService userService; @Test public void testCreate() { userService.countAll(); } }
基础工作做好,接下来我们详细看看 Spring基于 JDK动态代理 和 CGLIB类级别代理到底有什么区别。
二、基于JDK动态代理:
- <tx:annotation-driven transaction-manager="txManager"/>
<tx:annotation-driven transaction-manager="txManager"/>
该配置方式默认就是JDK动态代理方式
运行单元测试,核心日志如下:
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Creating new transaction with name [cn.javass.common.service.impl.BaseService.countAll]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT; '' //开启事务
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Opened new Session
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Bound value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] to thread [main] //绑定session到ThreadLocal
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Initializing transaction synchronization
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.interceptor.TransactionInterceptor - Getting transaction for [cn.javass.common.service.impl.BaseService.countAll]
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] bound to thread [main]
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Found thread-bound Session
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] bound to thread [main]
- Hibernate:
- select
- count(*) as col_0_0_
- from
- tbl_user usermodel0_
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Committing Hibernate transaction on Session //提交事务
- 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Removed value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] from thread [main] //解除绑定session到ThreadLocal
2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Creating new transaction with name [cn.javass.common.service.impl.BaseService.countAll]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT; '' //开启事务 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Opened new Session 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Bound value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] to thread [main] //绑定session到ThreadLocal 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Initializing transaction synchronization 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.interceptor.TransactionInterceptor - Getting transaction for [cn.javass.common.service.impl.BaseService.countAll] 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] bound to thread [main] 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Found thread-bound Session 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] bound to thread [main] Hibernate: select count(*) as col_0_0_ from tbl_user usermodel0_ 2012-03-07 09:58:44 [main] DEBUG org.springframework.orm.hibernate4.HibernateTransactionManager - Committing Hibernate transaction on Session //提交事务 2012-03-07 09:58:44 [main] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager - Removed value [org.springframework.orm.hibernate4.SessionHolder@1184a4f] for key [org.hibernate.internal.SessionFactoryImpl@107b56e] from thread [main] //解除绑定session到ThreadLocal
到此我们可以看到事务起作用了,也就是说即使把@Transactional放到接口上 基于JDK动态代理也是可以工作的。
三、基于CGLIB类代理:
- <tx:annotation-driven transaction-manager="txManager" proxy-target-class="true"/>
<tx:annotation-driven transaction-manager="txManager" proxy-target-class="true"/>
该配置方式是基于CGLIB类代理
启动测试会报错,No Session found for current thread,说明事务没有起作用
- org.hibernate.HibernateException: No Session found for current thread
- at org.springframework.orm.hibernate4.SpringSessionContext.currentSession(SpringSessionContext.java:97)
- at org.hibernate.internal.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:1024)
- at cn.javass.common.dao.hibernate4.BaseHibernateDao.getSession(BaseHibernateDao.java:63)
- at cn.javass.common.dao.hibernate4.BaseHibernateDao.aggregate(BaseHibernateDao.java:238)
- at cn.javass.common.dao.hibernate4.BaseHibernateDao.countAll(BaseHibernateDao.java:114)
- at cn.javass.common.service.impl.BaseService.countAll(BaseService.java:60)
- at cn.javass.common.service.impl.BaseService$$FastClassByCGLIB$$5b04dd69.invoke(<generated>)
- at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
- at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:618)
- at cn.javass.demo.service.impl.UserServiceImpl$$EnhancerByCGLIB$$7d46c567.countAll(<generated>)
- at cn.javass.ssonline.spider.service.impl.UserServiceTest2.testCreate(UserServiceTest2.java:20)
org.hibernate.HibernateException: No Session found for current thread at org.springframework.orm.hibernate4.SpringSessionContext.currentSession(SpringSessionContext.java:97) at org.hibernate.internal.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:1024) at cn.javass.common.dao.hibernate4.BaseHibernateDao.getSession(BaseHibernateDao.java:63) at cn.javass.common.dao.hibernate4.BaseHibernateDao.aggregate(BaseHibernateDao.java:238) at cn.javass.common.dao.hibernate4.BaseHibernateDao.countAll(BaseHibernateDao.java:114) at cn.javass.common.service.impl.BaseService.countAll(BaseService.java:60) at cn.javass.common.service.impl.BaseService$$FastClassByCGLIB$$5b04dd69.invoke(<generated>) at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149) at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:618) at cn.javass.demo.service.impl.UserServiceImpl$$EnhancerByCGLIB$$7d46c567.countAll(<generated>) at cn.javass.ssonline.spider.service.impl.UserServiceTest2.testCreate(UserServiceTest2.java:20)
如果将注解放在具体类上或具体类的实现方法上才会起作用。
- package cn.javass.common.service.impl;
- public abstract class BaseService<M extends java.io.Serializable, PK extends java.io.Serializable> implements IBaseService<M, PK> {
- @Transactional() //放在抽象类上
- @Override
- public int countAll() {
- return baseDao.countAll();
- }
- }
package cn.javass.common.service.impl; public abstract class BaseService<M extends java.io.Serializable, PK extends java.io.Serializable> implements IBaseService<M, PK> { @Transactional() //放在抽象类上 @Override public int countAll() { return baseDao.countAll(); } }
运行测试类,将发现成功了,因为我们的UserService继承该方法,但如果UserService覆盖该方法,如下所示,也将无法织入事务(报错):
- package cn.javass.demo.service.impl;
- public class UserServiceImpl extends BaseService<UserModel, Integer> implements UserService {
- //没有@Transactional
- @Override
- public int countAll() {
- return baseDao.countAll();
- }
- }
package cn.javass.demo.service.impl; public class UserServiceImpl extends BaseService<UserModel, Integer> implements UserService { //没有@Transactional @Override public int countAll() { return baseDao.countAll(); } }
四、基于aspectj的
- <tx:annotation-driven transaction-manager="txManager" mode="aspectj" proxy-target-class="true"/>
<tx:annotation-driven transaction-manager="txManager" mode="aspectj" proxy-target-class="true"/>
在此就不演示了,我们主要分析基于JDK动态代理和CGLIB类代理两种的区别。
五、结论:
基于JDK动态代理 ,可以将@Transactional放置在接口和具体类上。
基于CGLIB类代理,只能将@Transactional放置在具体类上。
因此 在实际开发时全部将@Transactional放到具体类上,而不是接口上。
六、分析
1、 JDK动态代理
1.1、Spring使用JdkDynamicAopProxy实现代理:
- package org.springframework.aop.framework;
- final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {
- //注意此处的method 一定是接口上的method(因此放置在接口上的@Transactional是可以发现的)
- public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
- }
- }
package org.springframework.aop.framework; final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable { //注意此处的method 一定是接口上的method(因此放置在接口上的@Transactional是可以发现的) public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { } }
注意此处的method 一定是接口上的method(因此放置在接口上的@Transactional是可以发现的)
1.2、如果<tx:annotation-driven 中 proxy-target-class="true" ,Spring将使用CGLIB动态代理,而内部通过Cglib2AopProxy实现代理,而内部通过DynamicAdvisedInterceptor进行拦截:
- package org.springframework.aop.framework;
- final class Cglib2AopProxy implements AopProxy, Serializable {
- private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable {
- //注意此处的method 一定是具体类上的method(因此只用放置在具体类上的@Transactional是可以发现的)
- public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
- }
- }
- }
package org.springframework.aop.framework; final class Cglib2AopProxy implements AopProxy, Serializable { private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable { //注意此处的method 一定是具体类上的method(因此只用放置在具体类上的@Transactional是可以发现的) public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable { } } }
1.3、Spring使用AnnotationTransactionAttributeSource通过查找一个类或方法是否有@Transactional注解事务来返回TransactionAttribute(表示开启事务):
- package org.springframework.transaction.annotation;
- public class AnnotationTransactionAttributeSource extends AbstractFallbackTransactionAttributeSource implements Serializable {
- protected TransactionAttribute determineTransactionAttribute(AnnotatedElement ae) {
- for (TransactionAnnotationParser annotationParser : this.annotationParsers) {
- TransactionAttribute attr = annotationParser.parseTransactionAnnotation(ae);
- if (attr != null) {
- return attr;
- }
- }
- return null;
- }
- }
package org.springframework.transaction.annotation; public class AnnotationTransactionAttributeSource extends AbstractFallbackTransactionAttributeSource implements Serializable { protected TransactionAttribute determineTransactionAttribute(AnnotatedElement ae) { for (TransactionAnnotationParser annotationParser : this.annotationParsers) { TransactionAttribute attr = annotationParser.parseTransactionAnnotation(ae); if (attr != null) { return attr; } } return null; } }
而AnnotationTransactionAttributeSource又使用SpringTransactionAnnotationParser来解析是否有@Transactional注解:
- package org.springframework.transaction.annotation;
- public class SpringTransactionAnnotationParser implements TransactionAnnotationParser, Serializable {
- public TransactionAttribute parseTransactionAnnotation(AnnotatedElement ae) {
- Transactional ann = AnnotationUtils.getAnnotation(ae, Transactional.class);
- if (ann != null) {
- return parseTransactionAnnotation(ann);
- }
- else {
- return null;
- }
- }
- public TransactionAttribute parseTransactionAnnotation(Transactional ann) {
- }
- }
package org.springframework.transaction.annotation; public class SpringTransactionAnnotationParser implements TransactionAnnotationParser, Serializable { public TransactionAttribute parseTransactionAnnotation(AnnotatedElement ae) { Transactional ann = AnnotationUtils.getAnnotation(ae, Transactional.class); if (ann != null) { return parseTransactionAnnotation(ann); } else { return null; } } public TransactionAttribute parseTransactionAnnotation(Transactional ann) { } }
此处使用AnnotationUtils.getAnnotation(ae, Transactional.class); 这个方法只能发现当前方法/类上的注解,不能发现父类的注解。 Spring还提供了一个 AnnotationUtils.findAnnotation()方法 可以发现父类/父接口中的注解(但spring没有使用该接口)。
如果Spring此处换成AnnotationUtils.findAnnotation(),将可以发现父类/父接口中的注解。
这里还一个问题,描述如下:
在接口中删除@Transactional //开启默认事务
- package cn.javass.common.service;
- public interface IBaseService<M extends java.io.Serializable, PK extends java.io.Serializable> {
- public int countAll();
- }
package cn.javass.common.service; public interface IBaseService<M extends java.io.Serializable, PK extends java.io.Serializable> { public int countAll(); }
在具体类中添加@Transactional
- package cn.javass.common.service.impl;
- public abstract class BaseService<M extends java.io.Serializable, PK extends java.io.Serializable> implements IBaseService<M, PK> {
- @Transactional() //开启默认事务
- @Override
- public int countAll() {
- return baseDao.countAll();
- }
- }
package cn.javass.common.service.impl; public abstract class BaseService<M extends java.io.Serializable, PK extends java.io.Serializable> implements IBaseService<M, PK> { @Transactional() //开启默认事务 @Override public int countAll() { return baseDao.countAll(); } }
问题:
我们之前说过,基于JDK动态代理时, method 一定是接口上的method(因此放置在接口上的@Transactional是可以发现的),但现在我们放在具体类上,那么Spring是如何发现的呢??
还记得发现TransactionAttribute是通过AnnotationTransactionAttributeSource吗?具体看步骤1.3:
而AnnotationTransactionAttributeSource 继承AbstractFallbackTransactionAttributeSource
- package org.springframework.transaction.interceptor;
- public abstract class AbstractFallbackTransactionAttributeSource implements TransactionAttributeSource {
- public TransactionAttribute getTransactionAttribute(Method method, Class<?> targetClass) {
- //第一次 会委托给computeTransactionAttribute
- }
- //计算TransactionAttribute的
- private TransactionAttribute computeTransactionAttribute(Method method, Class<?> targetClass) {
- //省略
- // Ignore CGLIB subclasses - introspect the actual user class.
- Class<?> userClass = ClassUtils.getUserClass(targetClass);
- // The method may be on an interface, but we need attributes from the target class.
- // If the target class is null, the method will be unchanged.
- //①此处将查找当前类覆盖的方法
- Method specificMethod = ClassUtils.getMostSpecificMethod(method, userClass);
- // If we are dealing with method with generic parameters, find the original method.
- specificMethod = BridgeMethodResolver.findBridgedMethod(specificMethod);
- // First try is the method in the target class.
- TransactionAttribute txAtt = findTransactionAttribute(specificMethod);
- if (txAtt != null) {
- return txAtt;
- }
- //找类上边的注解
- // Second try is the transaction attribute on the target class.
- txAtt = findTransactionAttribute(specificMethod.getDeclaringClass());
- if (txAtt != null) {
- return txAtt;
- }
- //②如果子类覆盖的方法没有 再直接找当前传过来的
- if (specificMethod != method) {
- // Fallback is to look at the original method.
- txAtt = findTransactionAttribute(method);
- if (txAtt != null) {
- return txAtt;
- }
- // Last fallback is the class of the original method.
- return findTransactionAttribute(method.getDeclaringClass());
- }
- return null;
- }
- }
package org.springframework.transaction.interceptor; public abstract class AbstractFallbackTransactionAttributeSource implements TransactionAttributeSource { public TransactionAttribute getTransactionAttribute(Method method, Class<?> targetClass) { //第一次 会委托给computeTransactionAttribute } //计算TransactionAttribute的 private TransactionAttribute computeTransactionAttribute(Method method, Class<?> targetClass) { //省略 // Ignore CGLIB subclasses - introspect the actual user class. Class<?> userClass = ClassUtils.getUserClass(targetClass); // The method may be on an interface, but we need attributes from the target class. // If the target class is null, the method will be unchanged. //①此处将查找当前类覆盖的方法 Method specificMethod = ClassUtils.getMostSpecificMethod(method, userClass); // If we are dealing with method with generic parameters, find the original method. specificMethod = BridgeMethodResolver.findBridgedMethod(specificMethod); // First try is the method in the target class. TransactionAttribute txAtt = findTransactionAttribute(specificMethod); if (txAtt != null) { return txAtt; } //找类上边的注解 // Second try is the transaction attribute on the target class. txAtt = findTransactionAttribute(specificMethod.getDeclaringClass()); if (txAtt != null) { return txAtt; } //②如果子类覆盖的方法没有 再直接找当前传过来的 if (specificMethod != method) { // Fallback is to look at the original method. txAtt = findTransactionAttribute(method); if (txAtt != null) { return txAtt; } // Last fallback is the class of the original method. return findTransactionAttribute(method.getDeclaringClass()); } return null; } }
//①此处将查找子类覆盖的方法
Method specificMethod = ClassUtils.getMostSpecificMethod(method, userClass);
// ClassUtils.getMostSpecificMethod
public static Method getMostSpecificMethod(Method method, Class<?> targetClass) {
Method specificMethod = null;
if (method != null && isOverridable(method, targetClass) &&
targetClass != null && !targetClass.equals(method.getDeclaringClass())) {
try {
specificMethod = ReflectionUtils.findMethod(targetClass, method.getName(), method.getParameterTypes());
} catch (AccessControlException ex) {
// security settings are disallowing reflective access; leave
// 'specificMethod' null and fall back to 'method' below
}
}
return (specificMethod != null ? specificMethod : method);
}
可以看出将找到当前类的那个方法。因此我们放置在BaseService countAll方法上的@Transactional起作用了。
//②如果子类覆盖的方法没有 再直接找当前传过来的
if (specificMethod != method) {
// Fallback is to look at the original method.
txAtt = findTransactionAttribute(method);
if (txAtt != null) {
return txAtt;
}
// Last fallback is the class of the original method.
return findTransactionAttribute(method.getDeclaringClass());
}
查找子类失败时直接使用传过来的方法。
因此,建议大家使用基于Schema风格的事务(不用考虑这么多问题,也不用考虑是类还是方法)。而@Transactional建议放置到具体类上,不要放置到接口。