spring aop之对象内部方法间的嵌套失效

Posted 2020-08-02 A_Beaver

spring aop之对象内部方法间的嵌套失效

先看一下spring 代理原理：

*       spring代理嵌套方法调用不生效
 * 
 *       Spring AOP defaults to using standard JDK dynamic proxies for AOP
 *       proxies. This enables any interface (or set of interfaces) to be
 *       proxied.
 * 
 *       Spring AOP can also use CGLIB proxies. This is necessary to proxy
 *       classes rather than interfaces. CGLIB is used by default if a business
 *       object does not implement an interface. As it is good practice to
 *       program to interfaces rather than classes; business classes normally
 *       will implement one or more business interfaces. It is possible to force
 *       the use of CGLIB, in those (hopefully rare) cases where you need to
 *       advise a method that is not declared on an interface, or where you need
 *       to pass a proxied object to a method as a concrete type.
 * 
 *       It is important to grasp the fact that Spring AOP is proxy-based. See
 *       Section 11.6.1, “Understanding AOP proxies” for a thorough examination
 *       of exactly what this implementation detail actually means.
 * 
 * 
 * 
 *       通过配置 <aop:aspectj-autoproxy proxy-target-class="true" />可以统一用CGLIB
 *       proxies。
 * 

实际上注入到spring容器的类实例是代理类，自然我们调用类的方法都能被aop拦截，但是类中内部方法的调用即this.metho(...), 这里的this，并不是spirng生成的代理类实例，而是实际产生的原对象，自然，aop就不会拦截这样的方法调用。

写个简短的程序验证一下spring代理嵌套方法调用不生效。

package com.doctor.aop.demo;

import org.springframework.stereotype.Component;

/**
 * @description 
 *
 * @author sdcuike
 *
 * @date 2016年6月24日 下午6:44:32
 */
@Component
public class Demo {
	public void test01() {
		System.out.println("test1");
		System.out.println("this对象指的不是代理类对象，而是原对象" + this.getClass());
		test02("hello nest ");
	}
	
	public String test02(String name) {
		return name;
	}
}

package com.doctor.aop.demo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @description
 *
 * @author sdcuike
 *
 * @date 2016年6月24日 下午6:44:12
 * 
 *       spring代理嵌套方法调用不生效
 * 
 *       Spring AOP defaults to using standard JDK dynamic proxies for AOP
 *       proxies. This enables any interface (or set of interfaces) to be
 *       proxied.
 * 
 *       Spring AOP can also use CGLIB proxies. This is necessary to proxy
 *       classes rather than interfaces. CGLIB is used by default if a business
 *       object does not implement an interface. As it is good practice to
 *       program to interfaces rather than classes; business classes normally
 *       will implement one or more business interfaces. It is possible to force
 *       the use of CGLIB, in those (hopefully rare) cases where you need to
 *       advise a method that is not declared on an interface, or where you need
 *       to pass a proxied object to a method as a concrete type.
 * 
 *       It is important to grasp the fact that Spring AOP is proxy-based. See
 *       Section 11.6.1, “Understanding AOP proxies” for a thorough examination
 *       of exactly what this implementation detail actually means.
 * 
 * 
 * 
 *       通过配置 <aop:aspectj-autoproxy proxy-target-class="true" />可以统一用CGLIB
 *       proxies。
 * 
 */
public class MethodInvokeTimeAspectTest {

	public static void main(String[] args) {
		ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(
				"classpath:/aopDemo1/spring-aop.xml");
		Demo demo = applicationContext.getBean(Demo.class);
		demo.test01();
		demo.test02("doctor who");
		System.out.println("注入到spring容器的类实例是代理类" + demo.getClass());
		// class com.doctor.aop.demo.Demo$$EnhancerBySpringCGLIB$$e9a9050a
		// 注入到spring容器的类实例是代理类

		InterfaceDemo interfaceDemo = applicationContext.getBean(InterfaceDemo.class);
		System.out.println("注入到spring容器的类实例是代理类" + interfaceDemo.getClass());
		interfaceDemo.testAnother();
		applicationContext.close();
	}

}

看一下输出：

07-03 11:23:57.357 main  INFO  org.springframework.context.support.ClassPathXmlApplicationContext -	Refreshing org[email protected]9f70c54: startup date [Sun Jul 03 11:23:57 CST 2016]; root of context hierarchy
07-03 11:23:57.457 main  INFO  org.springframework.beans.factory.xml.XmlBeanDefinitionReader -	Loading XML bean definitions from class path resource [aopDemo1/spring-aop.xml]
AspectAopDemo===before  execution(void com.doctor.aop.demo.Demo.test01())
test1
this对象指的不是代理类对象，而是原对象class com.doctor.aop.demo.Demo
AspectAopDemo===before  execution(String com.doctor.aop.demo.Demo.test02(String))
AspectAopDemo===after   execution(String com.doctor.aop.demo.Demo.test02(String))
AspectAopDemo===after   execution(void com.doctor.aop.demo.Demo.test01())
07-03 11:23:59.108 main  INFO  com.doctor.aop.demo.MethodInvokeTimeAspect -	[execution(void com.doctor.aop.demo.Demo.test01())],[],[null], [20] 
AspectAopDemo===before  execution(String com.doctor.aop.demo.Demo.test02(String))
AspectAopDemo===after   execution(String com.doctor.aop.demo.Demo.test02(String))
07-03 11:23:59.108 main  INFO  com.doctor.aop.demo.MethodInvokeTimeAspect -	[execution(String com.doctor.aop.demo.Demo.test02(String))],[doctor who],[doctor who], [0] 
注入到spring容器的类实例是代理类class com.doctor.aop.demo.Demo$$EnhancerBySpringCGLIB$$595bc0d7
注入到spring容器的类实例是代理类class com.sun.proxy.$Proxy7
07-03 11:23:59.108 main  INFO  org.springframework.context.support.ClassPathXmlApplicationContext -	Closing org[email protected]9f70c54: startup date [Sun Jul 03 11:23:57 CST 2016]; root of context hierarchy

日志结果：注入到spring容器内的类实例是代理类实例，非原实例，而类内方法之间调用的时候，this指向的是原实例，非代理类。

由spring代理是动态的，运行时织入，固类内部方法之间调用的时候，不可能让this指向代理类。

源码地址：https://github.com/sdcuike/spring-demo/blob/master/src/main/java/com/doctor/aop/demo/MethodInvokeTimeAspectTest.java

如何解决

 动态代理不行，我们基于字节码的支持编译期间进行织入(weaving)，还是编译后(post-compile)的AspectJ。

package com.doctor.aop.aspect.demo;

/**
 * @description 
 *
 * @author sdcuike
 *
 * @date 2016年6月27日 下午1:51:14
 */
public aspect AspectAopDemo {
pointcut demo() : execution(* com.doctor.aop.demo.Demo.* (..));

before() : demo() {
	System.out.println("AspectAopDemo===before  " + thisJoinPoint);
}

after() : demo() {
	System.out.println("AspectAopDemo===after   " + thisJoinPoint);
 }
}

package com.doctor.aop.demo;

import org.springframework.stereotype.Component;

/**
 * @description 
 *
 * @author sdcuike
 *
 * @date 2016年6月24日 下午6:44:32
 */
@Component
public class Demo {
	public void test01() {
		System.out.println("test1");
		System.out.println("this对象指的不是代理类对象，而是原对象" + this.getClass());
		test02("hello nest ");
	}
	
	public String test02(String name) {
		return name;
	}
}

看一下结果：eclipse IDE中把项目转变成AspectJ项目。

运行下面程序：（AspectJ/java application）

package com.doctor.aop.aspect.demo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.doctor.aop.demo.Demo;

/**
 * @description
 *
 * @author sdcuike
 *
 * @date 2016年6月27日 下午2:16:57
 * 
 *       aspect 编译时候注入，克服动态代理方法嵌套调用失效问题.
 * 
 *       运行方法：把项目转换成AspectJ工程，运行的时候选择：Run As-> AspectJ/Java Application
 */
class AspectAopDemoTest {

	public static void main(String[] args) {
		ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(
				"classpath:/aopDemo1/spring-aop2.xml");
		Demo demo = applicationContext.getBean(Demo.class);
		demo.test01();
		demo.test02("doctor who");
		System.out.println("注入到spring容器的类实例是代理类" + demo.getClass());
		// class com.doctor.aop.demo.Demo$$EnhancerBySpringCGLIB$$e9a9050a
		// 注入到spring容器的类实例是代理类

		applicationContext.close();
	}

}

输出结果：

07-03 12:04:48.375 main  INFO  org.springframework.context.support.ClassPathXmlApplicationContext -	Refreshing org[email protected]13c78c0b: startup date [Sun Jul 03 12:04:48 CST 2016]; root of context hierarchy
07-03 12:04:48.421 main  INFO  org.springframework.beans.factory.xml.XmlBeanDefinitionReader -	Loading XML bean definitions from class path resource [aopDemo1/spring-aop2.xml]
AspectAopDemo===before  execution(void com.doctor.aop.demo.Demo.test01())
test1
this对象指的不是代理类对象，而是原对象class com.doctor.aop.demo.Demo
AspectAopDemo===before  execution(String com.doctor.aop.demo.Demo.test02(String))
AspectAopDemo===after   execution(String com.doctor.aop.demo.Demo.test02(String))
AspectAopDemo===after   execution(void com.doctor.aop.demo.Demo.test01())
AspectAopDemo===before  execution(String com.doctor.aop.demo.Demo.test02(String))
AspectAopDemo===after   execution(String com.doctor.aop.demo.Demo.test02(String))
注入到spring容器的类实例是代理类class com.doctor.aop.demo.Demo
07-03 12:04:48.794 main  INFO  org.springframework.context.support.ClassPathXmlApplicationContext -	Closing org[email protected]13c78c0b: startup date [Sun Jul 03 12:04:48 CST 2016]; root of context hierarchy

test02方法确实被调用了4次。

使用AspectJ的一个间接局限是，因为AspectJ通知可以应用于POJO之上，它有可能将通知应用于一个已配置的通知之上。对于一个你没有注意到这方面问题的大范围应用的通知，这有可能导致一个无限循环。

具体更详细的参考：http://www.oschina.net/translate/comparative_analysis_between_spring_aop_and_aspectj