关于TransactionProxyFactoryBean

       	   <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
       	   		<property name="dataSource">
       	   			<ref local="dataSource"></ref>
       	   		</property>
       	   </bean>
           <bean id="baseTransactionProxy" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
           		<property name="transactionManager">
           			<ref local="transactionManager" />
           		</property>
           		<property name="transactionAttributes">
           			<props>
           				<prop key="update">PROPAGATION_REQUIRED</prop>
           			</props>
           		</property>
           </bean>
           
           <bean id="service" parent="baseTransactionProxy">
           		<property name="target">
           			<ref local="service_target" />
           		</property>
           </bean>
           
           <bean id="service_target" class="test.spring.transaction.TestService" />

以上是spring声明式事务的一种方式。

当调用context.getBean("service")，代理的生成过程是怎样的？


TransactionProxyFactoryBean的父类AbstractSingletonProxyFactoryBean中有个方法afterPropertiesSet，在这个方法中（afterPropertiesSet方法是spring在初始化bean的的过程中，会调用该方法，通过实现该方法，为bean提供一些特定的行为。），会产生一个代理。

	public void afterPropertiesSet() {
		if (this.target == null) {
			throw new IllegalArgumentException("Property 'target' is required");
		}
		if (this.target instanceof String) {
			throw new IllegalArgumentException("'target' needs to be a bean reference, not a bean name as value");
		}
		if (this.proxyClassLoader == null) {
			this.proxyClassLoader = ClassUtils.getDefaultClassLoader();
		}

		ProxyFactory proxyFactory = new ProxyFactory();

		if (this.preInterceptors != null) {
			for (Object interceptor : this.preInterceptors) {
				proxyFactory.addAdvisor(this.advisorAdapterRegistry.wrap(interceptor));
			}
		}

		// Add the main interceptor (typically an Advisor).
		proxyFactory.addAdvisor(this.advisorAdapterRegistry.wrap(createMainInterceptor()));

		if (this.postInterceptors != null) {
			for (Object interceptor : this.postInterceptors) {
				proxyFactory.addAdvisor(this.advisorAdapterRegistry.wrap(interceptor));
			}
		}

		proxyFactory.copyFrom(this);

		TargetSource targetSource = createTargetSource(this.target);
		proxyFactory.setTargetSource(targetSource);

		if (this.proxyInterfaces != null) {
			proxyFactory.setInterfaces(this.proxyInterfaces);
		}
		else if (!isProxyTargetClass()) {
			// Rely on AOP infrastructure to tell us what interfaces to proxy.
			proxyFactory.setInterfaces(
					ClassUtils.getAllInterfacesForClass(targetSource.getTargetClass(), this.proxyClassLoader));
		}

		this.proxy = proxyFactory.getProxy(this.proxyClassLoader);
	}

spring 在bean生成之后，判断bean是否为FactoryBean，具体在AbstractBeanFactory的
getObjectForBeanInstance中。

如果是FactoryBean，将使用FactoryBeanRegistrySupport类（DetautListableFactory的父类）中的doGetObjectFromFactoryBean方法

	private Object doGetObjectFromFactoryBean(
			final FactoryBean factory, final String beanName, final boolean shouldPostProcess)
			throws BeanCreationException {

		Object object;
		try {
			if (System.getSecurityManager() != null) {
				AccessControlContext acc = getAccessControlContext();
				try {
					object = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
						public Object run() throws Exception {
								return factory.getObject();
							}
						}, acc);
				}
				catch (PrivilegedActionException pae) {
					throw pae.getException();
				}
			}
			else {
				object = factory.getObject();
			}
		}
		catch (FactoryBeanNotInitializedException ex) {
			throw new BeanCurrentlyInCreationException(beanName, ex.toString());
		}
		catch (Throwable ex) {
			throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
		}

		
		// Do not accept a null value for a FactoryBean that's not fully
		// initialized yet: Many FactoryBeans just return null then.
		if (object == null && isSingletonCurrentlyInCreation(beanName)) {
			throw new BeanCurrentlyInCreationException(
					beanName, "FactoryBean which is currently in creation returned null from getObject");
		}

		if (object != null && shouldPostProcess) {
			try {
				object = postProcessObjectFromFactoryBean(object, beanName);
			}
			catch (Throwable ex) {
				throw new BeanCreationException(beanName, "Post-processing of the FactoryBean's object failed", ex);
			}
		}

		return object;
	}

可以看到该方法中

object = factory.getObject();

调用了FactoryBean的getObjcet。

那么从AbstractSingletonProxyFactoryBean（TransactionProxyFactoryBean的父类）中的getObject方法中看到

	public Object getObject() {
		if (this.proxy == null) {
			throw new FactoryBeanNotInitializedException();
		}
		return this.proxy;
	}

方法返回了上面(afterPropertiesSet方法中生成的代理)产生的代理类。

因此getBean获取的是一个代理（jdk代理或cgLib代理）。