Spring自定义BeanPostProcessor实现bean的代理

上文中：https://blog.csdn.net/qq_26437925/article/details/145241149 大致了解了spring aop的代理的实现，其实就是有个BeanPostProcessor代理了bean对象。

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本文直接编写最简单的代码直观感受下

bean A:

@Service
public class A {public A() {System.out.println("A()");}public void say(){System.out.println("say A");}
}

• beanPostProcessor

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Service;import java.lang.reflect.Method;@Service
public class ABeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {if (beanName.equals("a")) {System.out.println("a BeanPostProcessor postProcessAfterInitialization");return getProxy(bean);}return bean;}public Object getProxy(Object targetObject) {Enhancer enhancer = new Enhancer();Class<?> superClass = targetObject.getClass();enhancer.setSuperclass(superClass);MethodInterceptor interceptor = new MethodInterceptor() {@Overridepublic Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {System.out.println("cglib before...");Object res = methodProxy.invokeSuper(o, objects);return res;}};enhancer.setCallback(interceptor);Object targetProxy = enhancer.create();return targetProxy;}
}

基于cglib代理

<dependency><groupId>cglib</groupId><artifactId>cglib</artifactId><version>3.3.0</version>
</dependency>

• config类不用EnableAspectJAutoProxy了

@Configuration
@ComponentScan("com.aop.dependency")
public class ConfigOne {
}

• 测试类

@Test 
public void test() throws Exception {ApplicationContext ctx =new AnnotationConfigApplicationContext(ConfigOne.class);A a = (A) ctx.getBean("a");a.say();((AnnotationConfigApplicationContext) ctx).close();
}

测试输出

方法执行的代理输出正常

因为Cglib是用父类继承，新增了一个完整的class字节码。所以可以看到A()构造函数执行了两次, 一次是spring bean生命周期的实例化，一次则是Cglib创建出代理对象执行的。