用JDK DyProxy 模拟 AOP 实现

package test;
import java.lang.reflect.*;
/**
 * Created with IntelliJ IDEA.
 * User: e513480
 * Date: 12/3/13
 * Time: 4:39 PM
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 */
interface SomeInterface {
    public String someMethod(String val);
}
class SomeBean implements SomeInterface {
    @Override
    public String someMethod(String val) {
        System.out.println("some method invoked, val=" + val);
        if ("throw1".equalsIgnoreCase(val)) {
            throw new IllegalArgumentException("This is a Exception");
        } else if ("throw2".equalsIgnoreCase(val)) {
            throw new IllegalStateException("This is a Exception");
        }
        return val;
    }
}
class InvocationHandlerAdapter implements InvocationHandler {
    private Object proxyedObject;
    private Advice advice;
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Object ret = null;
        try {
            advice.doBeforeInvoke(proxyedObject, method, args);
            ret = method.invoke(proxyedObject, args);
            advice.doAfterSuccessInvoke(proxyedObject, method, args);
        } catch (InvocationTargetException e) {
            advice.doAfterThrows(proxyedObject, method, args, e.getCause());
        } finally {
            advice.doAfterInvoke(proxyedObject, method, args);
        }
        return ret;
    }
    public Object getProxyedObject() {
        return proxyedObject;
    }
    public void setProxyedObject(Object proxyedObject) {
        this.proxyedObject = proxyedObject;
    }
    public Advice getAdvice() {
        return advice;
    }
    public void setAdvice(Advice advice) {
        this.advice = advice;
    }
}
interface Advice {
    void doBeforeInvoke(Object proxyedObject, Method method, Object[] args);
    void doAfterSuccessInvoke(Object proxyedObject, Method method, Object[] args);
    void doAfterInvoke(Object proxyedObject, Method method, Object[] args);
    void doAfterThrows(Object proxyedObject, Method method, Object[] args, Throwable e) throws Throwable;
}
public class ProxyTest {
    private static  T createProxy(String beanName, Advice advice) {
        T proxy = null;
        try {
            InvocationHandlerAdapter handler = new InvocationHandlerAdapter();
            handler.setAdvice(advice);
            Class toBeProxedClass = Class.forName(beanName);
            handler.setProxyedObject(toBeProxedClass.newInstance());
            proxy = (T) Proxy.newProxyInstance(toBeProxedClass.getClassLoader(), toBeProxedClass.getInterfaces(), handler);
        } catch (Exception e) {
            throw new IllegalArgumentException("Failed to create proxy.", e);
        }
        return proxy;
    }
    public static void main(String[] args) {
        try {
            String beanName = "test.SomeBean";
            Advice advice = new Advice() {
                @Override
                public void doBeforeInvoke(Object proxyedObject, Method method, Object[] args) {
                    System.out.println("doBeforeInvoke");
                }
                @Override
                public void doAfterSuccessInvoke(Object proxyedObject, Method method, Object[] args) {
                    System.out.println("doAfterSuccessInvoke");
                }
                @Override
                public void doAfterInvoke(Object proxyedObject, Method method, Object[] args) {
                    System.out.println("doAfterInvoke");
                }
                @Override
                public void doAfterThrows(Object proxyedObject, Method method, Object[] args, Throwable e) throws Throwable {
                    System.out.println("doAfterThrows, the exception is " + e);
                    if (e instanceof IllegalStateException) {
                        //throw2
                        throw e;
                    }
                }
            };
            SomeInterface proxy = createProxy(beanName, advice);
            System.out.println("------------begin---------------------");
            String val = proxy.someMethod("hello");
            System.out.println("returned val=" + val);
            System.out.println("------------end---------------------");
            System.out.println("------------begin---------------------");
            val = proxy.someMethod("throw1");
            System.out.println("returned val=" + val);
            System.out.println("------------end---------------------");
            System.out.println("------------begin---------------------");
            try {
                val = proxy.someMethod("throw2");
                System.out.println("should not get to here");
            } catch (IllegalStateException e) {
                System.out.println("should get to here");
            }
            System.out.println("returned val=" + val);
            System.out.println("------------end---------------------");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}