spring aop探寻之Before Advice

hehaibo

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	/**
	 * Return the AopProxyFactory that this ProxyConfig uses.
	 */
	public AopProxyFactory getAopProxyFactory() {
		return this.aopProxyFactory;
	}

1 接口的声明

/**
 * 应用服务管理
 * 
 * @author hehaibo
 * 
 */
public interface BiapAppService {

	public void insertApp(BiapApp biapApp);

	public void updateApp(BiapApp biapApp);

	public void deleteApp(BiapApp biapApp);

	public Paginator<BiapApp, BiapApp> getPaginatorApp(
			Paginator<BiapApp, BiapApp> biapApp);
	
	public BiapApp getBiapAppById(String appId);

}

2 接口的实现

public class BiapAppServiceImpl implements BiapAppService {

	@Autowired
	private BiapAppDAO biapAppDAO;
	
	public void insertApp(BiapApp biapApp) {
		this.biapAppDAO.insertApp(biapApp);
	}

	public void updateApp(BiapApp biapApp) {
		this.biapAppDAO.updateApp(biapApp);
	}

	public void deleteApp(BiapApp biapApp) {
		this.biapAppDAO.deleteAppById(biapApp.getId());
	}
	
	public Paginator<BiapApp, BiapApp> getPaginatorApp(
			Paginator<BiapApp, BiapApp> biapApp) {
		biapApp.setData(this.biapAppDAO.getObjectList(biapApp));
		biapApp.setCount(this.biapAppDAO.getCount(biapApp));
		return biapApp;
	}

	public BiapApp getBiapAppById(String appId) {
		return this.biapAppDAO.getBiapAppById(appId);
	}
}

3 BeforeAdvice 实现，简单打印调用方法，模拟记录

import java.lang.reflect.Method;

import org.springframework.aop.MethodBeforeAdvice;

/**
 * 方法调用记录
 * 
 * @author hehaibo
 * 
 */
public class InvokeRecordBeforeAdvice implements MethodBeforeAdvice {

	public void before(Method method, Object[] args, Object target)
			throws Throwable {
		System.out.println("invock method:" + target.getClass().getName() + "."
				+ method.getName());
	}

}

4 测试代码

import org.springframework.aop.framework.ProxyFactory;

import com.hhb.biap.base.test.BiapBizBaseTest;
import com.hhb.biap.interceptor.before.InvokeRecordBeforeAdvice;
import com.hhb.biap.model.BiapApp;
import com.hhb.biap.service.BiapAppService;
import com.hhb.biap.service.impl.BiapAppServiceImpl;

public class InvokeRecordBeforeAdviceTest extends BiapBizBaseTest {
	@Test
	public void testBeforeInterceptor() {
		//获得容器中的bean对象
		BiapAppServiceImpl biapAppService = (BiapAppServiceImpl) this.applicationContext
				.getBean("biapAppService");
		System.out.println(biapAppService);
		// 创建代理工厂
		ProxyFactory proxyFactory = new ProxyFactory();
//		proxyFactory.setInterfaces(new Class[]{BiapAppService.class});
		proxyFactory.setTarget(biapAppService);
//		proxyFactory.addAdvice(new InvokeRecordBeforeAdvice());
		BiapAppServiceImpl proxyBiapAppService = (BiapAppServiceImpl) proxyFactory
				.getProxy();
		BiapApp biapApp = proxyBiapAppService.getBiapAppById("biap");
		System.out.println(biapApp);
	}
}

5 运行结果

java.lang.ClassCastException: $Proxy12 cannot be cast to com.hhb.biap.service.impl.BiapAppServiceImpl
	at com.hhb.biap.interceptor.test.InvokeRecordBeforeAdviceTest.testBeforeInterceptor(InvokeRecordBeforeAdviceTest.java:16)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.springframework.test.context.junit4.SpringTestMethod.invoke(SpringTestMethod.java:160)
	at org.springframework.test.context.junit4.SpringMethodRoadie.runTestMethod(SpringMethodRoadie.java:233)
	at org.springframework.test.context.junit4.SpringMethodRoadie$RunBeforesThenTestThenAfters.run(SpringMethodRoadie.java:333)
	at org.springframework.test.context.junit4.SpringMethodRoadie.runWithRepetitions(SpringMethodRoadie.java:217)
	at org.springframework.test.context.junit4.SpringMethodRoadie.runTest(SpringMethodRoadie.java:197)
	at org.springframework.test.context.junit4.SpringMethodRoadie.run(SpringMethodRoadie.java:143)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.invokeTestMethod(SpringJUnit4ClassRunner.java:160)
	at org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:51)
	at org.junit.internal.runners.JUnit4ClassRunner$1.run(JUnit4ClassRunner.java:44)
	at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:27)
	at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:37)
	at org.junit.internal.runners.JUnit4ClassRunner.run(JUnit4ClassRunner.java:42)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:97)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

以上我们运行可以看出ClassCastException异常，因为我之前对biapAppService做了aop事务的拦截，所以从BeanFactory中获得的对象已经是代理对象[JDK动代理的对象]

<aop:config>
			<aop:advisor pointcut="execution(public * com.hhb.biap.service.impl.*.*(..))"
				advice-ref="biap_txAdvice" />
		</aop:config>

		<tx:advice id="biap_txAdvice" transaction-manager="biap_transactionManager" >
			<tx:attributes>
				<tx:method name="insert*" isolation="DEFAULT" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
				<tx:method name="update*" isolation="DEFAULT" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
				<tx:method name="delete*" isolation="DEFAULT" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
				<tx:method name="get*" read-only="true" propagation="SUPPORTS" />
				<tx:method name="query*" read-only="true" propagation="SUPPORTS" />
				<tx:method name="*" isolation="DEFAULT" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
			</tx:attributes>
		</tx:advice>

所以会报错，现在我们将aop的配置下使之不会被spring拦截到。再运行，输出结果

 com.hhb.biap.service.impl.BiapAppServiceImpl@6d3b92
 com.hhb.biap.model.BiapApp@cd83d8

从上面我们看出，并没有我想要输出的接口，因为我们没有调用增加一个增强

proxyFactory.addAdvice(new InvokeRecordBeforeAdvice())

结果再运行，打印出了我们想要的结果。

com.hhb.biap.service.impl.BiapAppServiceImpl@17b1d64
invock method:com.hhb.biap.service.impl.BiapAppServiceImpl.toString
invock method:com.hhb.biap.service.impl.BiapAppServiceImpl.getBiapAppById
 com.hhb.biap.model.BiapApp@13a0212

toString（）怎么会调用呢，因为我们调用代理对象的toString()方法，这是我后面加上去的，

System.out.println("代理对象："+ proxyBiapAppService);

这里Spring默认帮我们使用的是CGLIB代理机制，因为CGLIB代理拦截每个方法的调用

而这一切是怎么做到的呢，接下来我们看ProxyFactory这个类里面做了什么事情......

public class ProxyFactory extends ProxyCreatorSupport implements AopProxy {
/**
  * Create a new ProxyFactory.
  */
 public ProxyFactory() {
 }
//.......
}

我们看它父类的构造函数

public class ProxyCreatorSupport extends AdvisedSupport {

	/** The AopProxyFactory to use */
	private AopProxyFactory aopProxyFactory;

	/** List of AdvisedSupportListener */
	private List listeners = new LinkedList();

	/** Set to true when the first AOP proxy has been created */
	private boolean active = false;


	/**
	 * Create a new ProxyCreatorSupport instance.
	 */
	public ProxyCreatorSupport() {
		this.aopProxyFactory = new DefaultAopProxyFactory();
	}
//......

}

ProxyCreatorSupport 这个类我想我们很熟悉......

它为我们默认初始化了一个DefaultAopProxyFactory对象，而这个对象负责代理对象创建。接下来我们看

proxyFactory.getProxy()所干的事情

public Object getProxy() {
		return createAopProxy().getProxy();
	}

接下来我们看createAopProxy()所干的事情，调用时父类ProxyCreatorSupport的方法

/**
	 * Subclasses should call this to get a new AOP proxy. They should <b>not</b>
	 * create an AOP proxy with <code>this</code> as an argument.
	 */
	protected final synchronized AopProxy createAopProxy() {
		if (!this.active) {
			activate();
		}
		return getAopProxyFactory().createAopProxy(this);
	}

getAopProxyFactory()返回的就是spring默认给我们创建的一个对象，接下我们看看DefaultAopProxyFactory

这个类又是怎么回事

public class DefaultAopProxyFactory implements AopProxyFactory, Serializable {
          public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
		if (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()) {
				return new JdkDynamicAopProxy(config);
			}
			if (!cglibAvailable) {
				throw new AopConfigException(
						"Cannot proxy target class because CGLIB2 is not available. " +
						"Add CGLIB to the class path or specify proxy interfaces.");
			}
			return CglibProxyFactory.createCglibProxy(config);
		}
		else {
			return new JdkDynamicAopProxy(config);
		}
	} 
}

从上面我们可以看出，这个是真正创建代理对象的地方，而参数AdvisedSupport config就是我们ProxyFactory,因为ProxyFactory间接继承了AdvisedSupport

public class ProxyCreatorSupport extends AdvisedSupport {
//...
}

分析下这个方法，

config.isOptimize() 这个表示是否启用优化，是否可以用cglib创建对象，从方法可以看出，如我们指定了创建代理对象使用的接口，

proxyFactory.setInterfaces(new Class[]{BiapAppService.class});

将将会覆盖cglib的代理，这个config.isProxyTargetClass()也是同理，表示是否能代理类对象。这个hasNoUserSuppliedProxyInterfaces(config) 。从我们的测试代码中可以看出，这个我们都没有指定，所以这个条件hasNoUserSuppliedProxyInterfaces(config) 满足，所以我们看到是打印对象的时候也被拦截了。

接下来我们分析前面2个条件为什么没有满足，我们看AdvisedSupport 的继承和实现

public class AdvisedSupport extends ProxyConfig implements Advised {
      //...
}

我们再看

public class ProxyConfig implements Serializable {

	/** use serialVersionUID from Spring 1.2 for interoperability */
	private static final long serialVersionUID = -8409359707199703185L;


	private boolean proxyTargetClass = false;

	private boolean optimize = false;
                 //......
}

我想我们知道原因了。这就是spring美妙的设计给我们所带来的，我们只有去看看他们的源代码我们窥探到它有血有肉的地方。

最终的测试代码

public void testBeforeInterceptor() {
		//获得容器中的bean对象
		BiapAppServiceImpl biapAppService = (BiapAppServiceImpl) this.applicationContext
				.getBean("biapAppService");
		System.out.println(biapAppService);
		// 创建代理工厂
		ProxyFactory proxyFactory = new ProxyFactory();
//		proxyFactory.setOptimize(Boolean.TRUE);
//		proxyFactory.setProxyTargetClass(Boolean.TRUE);
		proxyFactory.setInterfaces(new Class[]{BiapAppService.class});
		proxyFactory.setTarget(biapAppService);
		proxyFactory.addAdvice(new InvokeRecordBeforeAdvice());
		//注意这里不能再用BiapAppServiceImpl转换，否则会报错，
		//因为我们返回的是代理对象
		BiapAppService proxyBiapAppService = (BiapAppService) proxyFactory
				.getProxy();
		System.out.println("代理对象："+ proxyBiapAppService);
		BiapApp biapApp = proxyBiapAppService.getBiapAppById("biap");
		System.out.println(biapApp);
	}

接下来我们看看类的设计图纸：