• 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

    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

    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

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

      d.MyRetrofit.java

    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

     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》

    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。

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  • 原文地址:https://www.cnblogs.com/tony-yang-flutter/p/12366584.html
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