java初探之代理模式

代理模式

代理模式一般有三种角色：

在这里插入图片描述

没有使用代理模式的话可能就会直接去操作真实的对象

加入代理模式就是加入了隔离把我们的真实对象与调用者隔离了一下(代理对象)

代理对象的好处？

使用者(client)跟真实的对象是没有直接的交集的。不会直接操作到真实对象

实例

//1.代理角色对象 定义了服务的接口
public interface Massage{void message();
}

//2.真实的实现类：提供马杀鸡服务的路西
public class Lucy implements Massage{@Overridepublic void message(){System.out.println("手法一流");}
}public class Alvin implements Massage{@Overridepublic void massage(){System.out.println("精通各种手法")}
}

//3.代理对象 马杀鸡经纪人
public class Agent implements Massage{private final Massage massage;public Agent(Massage massage){this.massage = massage;}//前置处理public void before(){System.out.println("前置开始");}//后置处理public void after(){System.out.println("后置处理");}@Overridepublic void massage(){before();massage.massage();after();}
}public class MyClass{public static void main(String[] args) throws Exception{//静态代理Massage massage = new Lucy();Agent agent = new Agent(massage);agent.massage();//没有直接跟lucy交互}

每个代理类只能为一个接口来服务

如果有多个功能就要写多个代理类如：

public class WashAgent implements Wash{@Overridepublic void wash(){}
}

想办法通过一个代理类实现全部的代理功能！->动态代理

public class MyClass{public static void main(String[] args) throws Exception{//动态代理 完成足浴与按摩Alvin alvin = new Alvin();//真实的要操作的对象//Proxy创建 动态代理对象Object o = Proxy.newProxyInstance(MyClass.class.getClassLoader(),new Class[]{Message.class,Wash.class},new InvocationHandler(){@OVerridepublic Object invoke(Object o,Method method,Object[] objects)throws Throwable{//System.out.println(o.toString()); 死循环 o就是Object o 调用o.任何方法都会进入invoke()中 就会一直调然后死循环//invoke(在那个对象上执行的方法，方法参数)return method.invoke(alvin,objects);}});Massage massage = (Massage) o;massage.massage();Wash wash = (Wash) o;wash.wash();}
}public class Alvin implements Massage,Wash{@Overridepublic void massage(){System.out.println("massage...");}@Overridepublic void wash(){System.out.println("washing...");}
}

源码解析

Proxy.class://生成 class数据 动态代理为我们创建的对象 
byte[] var22 = ProxyGenerator.generateProxyClass(var23,var2,var17);test:
private static void proxy() throws Exception{String name = Massage.class.getName()+"$Proxy0";//生成代理指定接口的class数据byte[] bytes = ProxyGenerator.generateProxyClass(name,new Class[]{Massage.class});FileOutputStream fos = new FileOutputStream("lib/"+name+".class");fos.wirte(bytes);fos.close();
}

com.enjoy.lib.Massage$Proxy0.classpublic final class Massage$Proxy0 extends Proxy implements Massage{public Massage$Proxy0(InvocationHandler var1)throws{//这里的invovationHandler就是new ProxyInstance传入的super(var1);}public final void massage() throws{try{//super.h===var1;//给接口赋值 这样newProxyInstance就会被回调出去super.h.invoke(this,m3,(Object][])null); }catch(Throwable var3){throw new UndeclaredThrowableException(var3);}}public final String toString() throws{try{return (String)super.h.invoke(this,m2,(Object[])null);}catch(Throwable var3){throw new UndeclaredThrowableException(var3);}}}

Retrofit实操

public interface WetherApi{@POST("/v3/weather/weatherInfo")@FormUrlEncodedCall<ResponseBody> getWeather(@Field("city") String city,@Field("key") String key);@GET("/v3/weather/weatherInfo")Call<ResponseBody> getWeather(@Query("city") String city,@Query("key") String key);
}Retrofit retrofit = new Retrofit.Builder().baseUrl("https://restapi.amap.com").build();//create()就是内部完成了动态代理 
WeatherApi weatherApi = retrofit.create(WetherApi.class);

public class EnjoyRetrofit{//第一次调用解析一次 第二次调用又去解析一次吗final Map<Method,ServiceMethod> serviceMethodCache = new ConcurrentHashMap<>();final Call.Factory callFactory;final HttpUrl baseUrl;EnjoyRetrofit(Call.Factory callFactory,HttpUrl baseUrl){this.callFactory = callFactory;this.baseUrl = baseUrl;}public <T> T create(final Class<T> service){return (T) Proxy.newInstance(service.getClassLoader(),new Class[]{service},new InvocationHandler(){@Overridepublic Object invoke(Object proxy,Method method,Object[] args) throws Throwable{//实现对应的postWeather/getWeather//解析method上所有的注解信息loadServiceMethod(method);return serviceMethod.invoke(args);//返回Call}});}//解析方法上的注解private ServiceMethod loadServiceMethod(Method method){//先不上锁 避免synchronized的性能损耗ServiceMethod result = serviceMethodCache.get(method);if(result!=null) return result;//多线程下避免重复解析synchronized(serviceCache){//线程A和B进入时 A先进 result=null 给result赋值后B进入 如果不判断是否为空 会再次解析一次 result = serviceCache.get(method);if(result==null){result = new ServiceMethod.Builder(this,method).build();serviceMethodCache.put(method,result);}}return result;}//构建者模式 不需要关心成员的细节 只需要关心你想要设置的内容  很好的屏蔽掉细节public static final class Builder{private HttpUrl baseUrl;private okhttp3.Call.Factory callFactory;public Builder callFactory(okhttp3.Call.Factory factory){this.callFactory = factory;return this;}public Builder baseUrl(String baseUrl){this.baseUrl = HttpUrl.get(baseUrl);return this;}public EnjoyRetrofit build(){if(baseUrl==null){throw new IllegalStateException("Base URL,required");}okhttp3.Call.Factory callFactory = this.callFactory;if(callFactory==null){callFactory = new OkHttpClient();}return new EnjoyRetrofit(callFactory,baseUrl);}}
}
//可以设置也可以不设置 build会进行校验  
EnjoyRetrofit.Builder().baseUrl("https").callFactory(new OkHttpClient.Builder().callTimeout(1)).build();

//记录请求类型 请求参数 完整地址
public class ServiceMethod{String baseUrl;private final okhttp3.Call.Factory callFactory;String httpMethod;String relativeUrl;Boolean hasBody;private FormBody.Builder formBuild;//每个参数的keyParameterHandler[] parameterHandler;HttpUrl.Builder urlBuilder;//完整的urlpublic ServiceMethod(Builder builder){baseUrl = builder.enjoyRetrofit.baseUrl;callFactory = builder.enjoyRetrofit.callFactory;httpMethod = builder.httpMethod;relativeUrl = builder.relativeUrl;hasBody = builder.hasBody;parameterHandler = builder.parameterHandler;//如果有请求体 创建 一个okhttp的请求体对象 if(hasBody){formBuild = new FormBody.Builder();}}public Object invoke(Object[] args){//处理请求的地址与参数 重点for(int i=0;i<parameterHandler.length;i++){ParameterHandler handlers = parameterHandler[i]; //handler记录了key//handler内本来就记录了key 现在给到了对应的valuehandlers.apply(this,args[i].toString());//this->ServiceMethod记录了请求地址 args[i]记录了参数的value}//获取最终请求地址HttpUrl url;if(urlBuilder ==null){//说明不是get请求urlBuilder = baseUrl.newBuilder(relativeUrl); }url = urlBuilder.build();//请求体FormBody formBody = null;if(formBuild!=null){formBody =  formBuild.build();}//使用okhttp发送请求 get请求时formBody==null没关系可以传入Request request = new Request.Builder().url(url).method(httpMethod,formBody).build();return callFactory.newCall(request);}//get请求 把k-v 拼到url里面public void addQueryParameter(String key,String value){if(urlBuilder ==null){urlBuilder = baseUrl.newBuilder(relativeUrl);}urlBuilder.addQuery(key,value);}//吧k-v放到请求体中public void addFieldParameter(String key,String value){formBuild.add(key,value);}public static class Builder{private final EnjoyRetrofit enjoyRetrofit;private final Annotation[] methodA nnotations;private final Annotation[][] parameterAnnotations;private String httpMethod;private String relativeUrl;private Boolean hasBody;private ParameterHandler[] parameterHandler;public Builder(EnjoyRetrofit enjoyRetrofit,Method method){this.enjoyRetrofit = enjoyRetrofit;//获取方法上的所有注解methodAnnotations = method.getAnnotations();//获得方法参数的所有的注解(一个参数可以有多个注解，一个方法又会有多个参数)paramterAnnotations = method.getParameterAnnotations();}public ServiceMethod build(){//1.解析方法上的注解 只处理POST和GETfor(Annotation methodAnnotation:methodAnnotations){if(methodAnnotation instance of POST){//post请求//记录当前请求方式this.httpMethod = "POST";//记录当前url的paththis.relativeUrl = ((POST) methodAnnotation).getValue();//是否有请求体this.hasBody = true;}else if(methodAnnotation instance of GET){this.httpMethod = "GET";this.relativeUrl = ((GET) methodAnnotation).getValue();this.hasBody = false;}}//2.解析方法参数的注解int length = paramterAnnotations.length;//有多少个参数parameterHandler = new ParameterHandler[length];for(int i=0;i< length;i++){//一个参数上面所有的注解Annotation[] annotations = parameterAnnotations[i];//处理参数上的每一个注解for(Annotation annotation:annotations){if(annotation instance of Field){//得到注解上的value 请求参数的keyString value = ((Field) annotation).getValue();//又在一个新的类中记录了请求参数的keyparameterHandler[i] = new ParameterHandler.FieldParameterHandler(value);}else if(annotation instance of Query){String value = ((Query) annotation).getValue();parameterHandler[i] = new ParameterHandler.QueryParameterHandler(value);}}}return new ServiceMethod(this);}} 
}

//
public abstract class ParameterHandler{abstract void apply(ServiceMethod serviceMethod,String value);//只处理get请求 没有请求头static class QueryParameterHandler extends ParameterHandler{String key;public QueryParameterHandler(String key){this.key = key;}@Overridevoid apply(ServiceMethod serviceMethod,String value){serviceMethod.addQueryParameter(key,value);//回调到serviceMethod中}}//只处理post请求 带请求头static class FiledParameterHander extends ParameterHandler{String key;public FiledParameterHandler(String key){this.key = key;}@Overridevoid apply(ServiceMethod serviceMethod,String value){serviceMethod.addFieldParameter(key,value);//回调到serviceMethod中}}
}

/回调到serviceMethod中
}
}

//只处理post请求 带请求头
static class FiledParameterHander extends ParameterHandler{String key;public FiledParameterHandler(String key){this.key = key;}@Overridevoid apply(ServiceMethod serviceMethod,String value){serviceMethod.addFieldParameter(key,value);//回调到serviceMethod中}
}

}