Android使用动态代理模仿Retrofit的create方法，使其可以返回任意的接口类型

一、概述

　　本节将模仿一下Retrofit的create泛型方法，根据传入的interface，生成一个代理对象。同个这个小例子可以加深对retrofit的理解

二、实际代码

　　定义一个book接口，通过动态带来创建其实现类，并调用其实现类的book方法

　　1.Book.java：普通的接口

　　2.ApiBookInterface.java：定义一个普通的接口

　　3.MyRetrofit.java：create方法生成代理对象

　　4.JavaBook.java 实现了Book.java接口的类

　　5.测试方法

　　a.Book.java

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package com.yw.rxjava3demo.proxy;   /**  * 所有书本的基类  * create by yangwei  * on 2020-02-26 12:16  */ public interface Book {     void read(); }

　　b.JavaBook.java

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package com.yw.rxjava3demo.proxy;   import com.yw.rxjava3demo.MyLog;   /**  * create by yangwei  * on 2020-02-26 12:17  */ public class JavaBook implements Book{     @Override     public void read() {         MyLog.log("《深入Java虚拟机》");       } }

　　c.ApiBookInterface.java

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package com.yw.rxjava3demo.proxy;   /**  * create by yangwei  * on 2020-02-26 12:24  */ public interface ApiBookInterface {     Book getBook(); }

　　d.MyRetrofit.java

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package com.yw.rxjava3demo.proxy;   import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy;   /**  * create by yangwei  * on 2020-02-26 12:18  */ public class MyRetrofit {     private ProxyBookAdapterFactory proxyBookAdapterFactory;       public MyRetrofit(ProxyBookAdapterFactory proxyBookAdapterFactory) {         this.proxyBookAdapterFactory = proxyBookAdapterFactory;     }       public <T> T create(final Class<T> bookClass) {         return (T) Proxy.newProxyInstance(bookClass.getClassLoader(), new Class<?>[]{bookClass}, new InvocationHandler() {             @Override             public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {                 //不走代理方法，直接走原始方法                 if (method.getDeclaringClass() == Object.class) {                     return method.invoke(this, args);                 }                 return new AndroidBook();             }         });     }           public static final class Builder {         private ProxyBookAdapterFactory proxyBookAdapterFactory;           public Builder setProxyBookAdapterFactory(ProxyBookAdapterFactory proxyBookAdapterFactory) {             this.proxyBookAdapterFactory = proxyBookAdapterFactory;             return this;         }           public MyRetrofit build() {             return new MyRetrofit(proxyBookAdapterFactory);         }     } }

　　e.测试方法

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ApiBookInterface apiBookInterface  = new com.yw.rxjava3demo.proxy.MyRetrofit.Builder().build().create(ApiBookInterface.class);        com.yw.rxjava3demo.proxy.Book book = apiBookInterface.getBook();        book.read();

　　f.测试结果，会输出《深入java虚拟机》

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1	2020-02-26 13:29:02.953 1604-1604/? E/MyLog: 《深入Java虚拟机》

　　总结：希望通过这个小例子大家能够对Proxy有更深的理解，同时也对Retrofit的create方法加深印象。