動態(tài)代理-Proxy

Warren 發(fā)布于2019-08-16 15:41 / 2722人閱讀

摘要：主要目的是記錄動態(tài)代理的實(shí)現(xiàn)，為的學(xué)習(xí)做鋪墊。什么是動態(tài)代理動態(tài)代理就是在運(yùn)行時為某個類生成代理，即在階段，沒有實(shí)際的文件與其對應(yīng)。話不多說，直接看動態(tài)代理的例子將該代理類保存下來，查看源碼

主要目的是記錄java動態(tài)代理的實(shí)現(xiàn)，為rpc的學(xué)習(xí)做鋪墊。

什么是動態(tài)代理？
動態(tài)代理就是在java運(yùn)行時為某個類生成代理，即在code階段，沒有實(shí)際的java文件與其對應(yīng)。

java實(shí)現(xiàn)動態(tài)代理的類就是反射包中的Proxy類。
話不多說，直接看動態(tài)代理的例子：

public class TestProxy {
    public static void main(String[] args) {
        PaoTui paoTuiProxy = (PaoTui)Proxy.newProxyInstance(
                PaoTui.class.getClassLoader(), 
                new Class[]{PaoTui.class},
                new InvocationHandler() {
                    Flan flan = new Flan();
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        return method.invoke(flan, args);
                    }}
                );

        paoTuiProxy.buySomething("an apple");
        System.out.println(paoTuiProxy.toString());
    }
}

interface PaoTui {
    void buySomething(String something);
}

class Flan implements PaoTui {
    @Override
    public void buySomething(String something) {
        System.out.println("Flan buys "+something+" for Remi");
    }
}

將該代理類保存下來，查看源碼：

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 PaoTui {
    private static Method m1;
    private static Method m2;
    private static Method m3;
    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 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 void buySomething(String var1) throws  {
        try {
            super.h.invoke(this, m3, new Object[]{var1});
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

    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", new Class[]{Class.forName("java.lang.Object")});
            m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
            m3 = Class.forName("PaoTui").getMethod("buySomething", new Class[]{Class.forName("java.lang.String")});
            m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}