如何获取动态代理生成的$Proxy0源码。

学习动态代理的过程中没有发现对invoke()方法进行调用的地方，需要看一下jdk的反射中Proxy和生成的代理类$Proxy0的源码。

IUserDao.java

package com.company;

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

public interface IUserDao {
    void save();
    void find();
}

class UserDao implements IUserDao{

    @Override
    public void save() {
        System.out.println("模拟：保存用户！");
    }

    @Override
    public void find() {
        System.out.println("模拟：查询！");
    }
}

/*
动态代理
 */
class ProxyFactory{
    private Object target;
    public ProxyFactory(Object target){
        this.target = target;
    }

    public Object getProxyInstance(){
        Object proxy = Proxy.newProxyInstance(
                target.getClass().getClassLoader(),
                target.getClass().getInterfaces(),
                new InvocationHandler() {
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        String methodName = method.getName();
                        Object result ="";
                        if ("find".equals(methodName)){
                            result = method.invoke(target,args);
                        } else {
                            result = method.invoke(target,args);
                        }
                        return result;
                    }
                }
        );
        return proxy;
    }
}

TEST.java

package com.company;

public class TEST {
    public static void main(String[] args) {
        //生成$Proxy0的class文件
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");

        IUserDao target = new UserDao();
        IUserDao proxy = (IUserDao) new ProxyFactory(target).getProxyInstance();

        System.out.println("目标对象：" + target.getClass());
        System.out.println("代理对象：" + proxy.getClass());
        System.out.println();

        proxy.save();
        System.out.println();
        proxy.find();
    }
}

注意：其中生成$Proxy0的class文件的代码不能放在结尾。

运行结果：

目标对象：class com.company.UserDao
代理对象：class com.sun.proxy.$Proxy0
模拟：保存用户！
模拟：查询！

运行后会自动在项目根目录生成com文件夹，其中...\IdeaProjects\com\sun\proxy下会生成$Proxy0.class文件。

通过对$Proxy0.class文件进行反编译（有很多方法、软件），能够得到$Proxy0.java文件。可以进一步学习。

$Proxy0.java

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.sun.proxy;

import com.company.IUserDao;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;

public final class $Proxy0 extends Proxy implements IUserDao {
    private static Method m1;
    private static Method m3;
    private static Method m4;
    private static Method m2;
    private static Method m0;

    public $Proxy0(InvocationHandler var1) throws  {
        super(var1);
    }

    public final boolean equals(Object var1) throws  {
        try {
            return ((Boolean)super.h.invoke(this, m1, new Object[]{var1})).booleanValue();
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

    public final void find() throws  {
        try {
            super.h.invoke(this, m3, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final void save() throws  {
        try {
            super.h.invoke(this, m4, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final String toString() throws  {
        try {
            return (String)super.h.invoke(this, m2, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final int hashCode() throws  {
        try {
            return ((Integer)super.h.invoke(this, m0, (Object[])null)).intValue();
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            m3 = Class.forName("com.company.IUserDao").getMethod("find");
            m4 = Class.forName("com.company.IUserDao").getMethod("save");
            m2 = Class.forName("java.lang.Object").getMethod("toString");
            m0 = Class.forName("java.lang.Object").getMethod("hashCode");
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}

ps：奇怪，今天又试了一下居然无法自动生成$Proxy0.class了。参考别人博客说手动创建路径和文件再运行也是可以的，但是没有成功。