本文共 8409 字，大约阅读时间需要 28 分钟。
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 */@Componentpublic 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 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.springframework.context.support.ClassPathXmlApplicationContext@9f70c54: startup date [Sun Jul 03 11:23:57 CST 2016]; root of context hierarchy07-03 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())test1this对象指的不是代理类对象，而是原对象class com.doctor.aop.demo.DemoAspectAopDemo===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.$Proxy707-03 11:23:59.108 main INFO org.springframework.context.support.ClassPathXmlApplicationContext - Closing org.springframework.context.support.ClassPathXmlApplicationContext@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。 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 */@Componentpublic 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(); }} 07-03 12:04:48.375 main INFO org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@13c78c0b: startup date [Sun Jul 03 12:04:48 CST 2016]; root of context hierarchy07-03 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())test1this对象指的不是代理类对象，而是原对象class com.doctor.aop.demo.DemoAspectAopDemo===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.Demo07-03 12:04:48.794 main INFO org.springframework.context.support.ClassPathXmlApplicationContext - Closing org.springframework.context.support.ClassPathXmlApplicationContext@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。 转载地址：http://steaf.baihongyu.com/