JDK动态代理

JDK动态代理

package com.xzp.active;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import org.springframework.cglib.proxy.Enhancer;

public class TransactionManageAdvice<T> implements InvocationHandler{

    T target;// 被代理的真实对象
    
    public void setTarget(T target) {
        this.target = target;
    }
    
    public <T> T getProxy() {
        return (T)Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
    }
    
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("增强了");
        //===================================================
        method.invoke(target, args);
        //===================================================
        System.out.println("后置增强");
        return null;
    }
   
}

底层源码:

package com.xzp.active;

import com.xzp.pojo.User;
import com.xzp.service.UserService;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;

public final class UserServiceProxy extends Proxy implements UserService
{
    static
    {
        try
        {
            m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
            m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
            m3 = Class.forName("com.xzp.service.UserService").getMethod("update", new Class[] { Class.forName("com.xzp.pojo.User") });
            m4 = Class.forName("com.xzp.service.UserService").getMethod("save", new Class[] { Class.forName("com.xzp.pojo.User") });
            m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
        }
        catch (Exception localNoSuchMethodException)
        {
        }
    }
    private static Method m1;
    private static Method m2;
    private static Method m3;
    private static Method m4;
    private static Method m0;

    public UserServiceProxy(InvocationHandler paramInvocationHandler)
    {
        super(paramInvocationHandler);
    }

    public final boolean equals(Object paramObject)
    {
        try
        {
            return ((Boolean)this.h.invoke(this, m1, new Object[] { paramObject })).booleanValue();
        }
        catch (Error|RuntimeException localError)
        {
            throw localError;
        }
        catch (Throwable localThrowable)
        {
            throw new UndeclaredThrowableException(localThrowable);
        }
    }

    public final String toString()
    {
        try
        {
            return (String)this.h.invoke(this, m2, null);
        }
        catch (Error|RuntimeException localError)
        {
            throw localError;
        }
        catch (Throwable localThrowable)
        {
            throw new UndeclaredThrowableException(localThrowable);
        }
    }

    public final void update(User paramUser)
    {
        try
        {
            this.h.invoke(this, m3, new Object[] { paramUser });
            return;
        }
        catch (Error|RuntimeException localError)
        {
            throw localError;
        }
        catch (Throwable localThrowable)
        {
            throw new UndeclaredThrowableException(localThrowable);
        }
    }

    public final void save(User paramUser)
    {
        try
        {
            this.h.invoke(this, m4, new Object[] { paramUser });
            return;
        }
        catch (Error|RuntimeException localError)
        {
            throw localError;
        }
        catch (Throwable localThrowable)
        {
            throw new UndeclaredThrowableException(localThrowable);
        }
    }

    public final int hashCode()
    {
        try
        {
            return ((Integer)this.h.invoke(this, m0, null)).intValue();
        }
        catch (Error|RuntimeException localError)
        {
            throw localError;
        }
        catch (Throwable localThrowable)
        {
            throw new UndeclaredThrowableException(localThrowable);
        }
    }

}

底层源码生成方式:

(通过ProxyGenerator类中的generateProxyClass方法指定真实对象的Class以及代理类名称来返回一个byte数组 将byte数组写入指定文件)

package com.xzp.active;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;

import com.xzp.service.impl.UserServiceImpl;

import sun.misc.ProxyGenerator;

public class Main {
	public static void main(String[] args) {
        generateClassFile(UserServiceImpl.class, "UserServiceProxy");
	}
	public static void generateClassFile(Class targetClass,String proxyName) {
		
		byte[] classFile = ProxyGenerator.generateProxyClass(proxyName, targetClass.getInterfaces());
		String path = targetClass.getResource(".").getPath();
		FileOutputStream out = null;
		try {
			out = new FileOutputStream(path + proxyName + ".class");
			out.write(classFile);
			out.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println(path);
	}
}