OKhttp拦截器实现实践环节源码解析

目录

• 正文
• 拦截器的自我实现
• RetryAndFollowUpInterceptor
• BridgeInterceptor
• CacheInterceptor
• ConnectInterceptor
• CallServerInterceptor
• 运行一下
• 题外话

正文

本节我们开始自我实现我们自己okhttp框架中的每个拦截器。

先简单回顾一下各个拦截器的作用：

• RetryAndFollowUpInterceptor：重试拦截器

处理重试的一个拦截器，会去处理一些异常，根据底层返回的响应数据，先进行一些特殊状态码的判断，例如：如果底层返回307，则根据服务端返回的最新location，重新构建新的请求，交由底层拦截器，重新发起请求。如果底层返回路由异常、某些IO异常，则会continue，重新发起请求。

• BridgeInterceptor：基础的拦截器

给我们平常发起的请求，添加通用和请求首部信息，做一个简单的处理，设置一些通用的请求头，Cookie、Connection、Content-Type、Content-Length，做一些返回的处理，如果返回的数据被压缩了，采用 ZipSource，保存Cookie。

• CacheInterceptor：缓存拦截器

缓存存储策略、缓存过期策略、缓存对比策略的具体实现。

• ConnectInterceptor：连接的拦截器

ConnectInterceptor负责连接复用、建立socket连接，okio与socket输入输出流绑定。

• CallServerInterceptor： 具体与服务器通信，给服务器写数据和读取数据；

拦截器的自我实现

好了，接下来，把我们之前写的框架的代码，重新梳理一下，新增一下几个拦截器。 RealCall.java

package com.itbird.okhttpstudy.okhttp;
import android.util.Log;
import com.itbird.okhttpstudy.interceptor.BridgeInterceptor;
import com.itbird.okhttpstudy.interceptor.CacheInterceptor;
import com.itbird.okhttpstudy.interceptor.CallServerInterceptor;
import com.itbird.okhttpstudy.interceptor.ConnectInterceptor;
import com.itbird.okhttpstudy.interceptor.Interceptor;
import com.itbird.okhttpstudy.interceptor.RetryAndFollowUpInterceptor;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
 * Created by itbird on 2022/11/21
 */
public class RealCall implements Call {
    private Request request;
    private OkhttpClient okhttpClient;
    public RealCall(Request request, OkhttpClient okhttpClient) {
        this.request = request;
        this.okhttpClient = okhttpClient;
    }
    @Override
    public void enqueue(Callback callback) {
        okhttpClient.dispatcher().enqueue(new AsyncCall(callback));
    }
    @Override
    public Response execute() {
        return getResponseWithInterceptorChain();
    }
    @Override
    public Request request() {
        return request;
    }
    private Response getResponseWithInterceptorChain() {
        List interceptors = new ArrayList();
        interceptors.add(new BridgeInterceptor());// 基础
        interceptors.add(new CacheInterceptor());// 缓存
        interceptors.add(new ConnectInterceptor());// 建立连接
        interceptors.add(new CallServerInterceptor());// 写数据
        interceptors.add(new RetryAndFollowUpInterceptor());// 重试
        Interceptor.Chain chain = new RealInterceptorChain(this, interceptors, request);
        try {
            return chain.proceed(request);
        } catch (IOException e) {
            //处理过程被中断时，通过错误码返回
            return null;
        }
    }
    class AsyncCall extends NamedRunnable {
        private Callback callback;
        public AsyncCall(Callback callback) {
            this.callback = callback;
        }
        @Override
        public void execute() {
            Log.d(Constants.TAG, "AsyncCall execute");
            //这里有问题的
            Response response = getResponseWithInterceptorChain();
            if (callback != null) {
                try {
                    callback.onResponse(RealCall.this, response);
                } catch (IOException e) {
                }
            }
        }
    }
}

接下来还是老办法，按照AS提示，新建这些类。

RetryAndFollowUpInterceptor

package com.itbird.okhttpstudy.interceptor;
import android.util.Log;
import com.itbird.okhttpstudy.okhttp.Constants;
import com.itbird.okhttpstudy.okhttp.Request;
import com.itbird.okhttpstudy.okhttp.Response;
import java.io.IOException;
/**
 * Created by itbird on 2022/11/24
 */
public class RetryAndFollowUpInterceptor implements Interceptor {
    @Override
    public Response intercept(Chain chain) throws IOException {
        Log.d(Constants.TAG, "RetryAndFollowUpInterceptor");
        Request request = chain.request();
        //okhttp表现为，此处，去根据底层抛出的异常，决定是否为关键错误异常，如果不是，则while true循环，去执行重试请求
        return chain.proceed(request);
    }
}

BridgeInterceptor

package com.itbird.okhttpstudy.interceptor;
import android.util.Log;
import com.itbird.okhttpstudy.okhttp.Constants;
import com.itbird.okhttpstudy.okhttp.Request;
import com.itbird.okhttpstudy.okhttp.RequsetBody;
import com.itbird.okhttpstudy.okhttp.Response;
import java.io.IOException;
/**
 * Created by itbird on 2022/11/24
 */
public class BridgeInterceptor implements Interceptor {
    public BridgeInterceptor() {
    }
    @Override
    public Response intercept(Chain chain) throws IOException {
        Log.d(Constants.TAG, "BridgeInterceptor");
        Request request = chain.request();
        // 添加一些请求头
//        request.addParam("Connection", "keep-alive");
        // 做一些其他处理
        if (request.requsetBody() != null) {
            RequsetBody requestBody = request.requsetBody();
            request.addParam("Content-Type", requestBody.getContentType());
            request.addParam("Content-Length", Long.toString(requestBody.getContentLength()));
        }
        //GZIP数据流转换
        return chain.proceed(request);
    }
}

CacheInterceptor

package com.itbird.okhttpstudy.interceptor;
import android.util.Log;
import com.itbird.okhttpstudy.okhttp.CacheControl;
import com.itbird.okhttpstudy.okhttp.Constants;
import com.itbird.okhttpstudy.okhttp.Request;
import com.itbird.okhttpstudy.okhttp.Response;
import java.io.IOException;
/**
 * Created by itbird on 2022/11/24
 */
public class CacheInterceptor implements Interceptor {
    public CacheInterceptor() {
    }
    @Override
    public Response intercept(Chain chain) throws IOException {
        Log.d(Constants.TAG, "CacheInterceptor");
        Request request = chain.request();
        if (request.cache() == CacheControl.FORCE_CACHE) {
            //本地缓存有没有，缓存过期了没有，缓存对比服务器返回307
        }
        return chain.proceed(request);
    }
}

ConnectInterceptor

package com.itbird.okhttpstudy.interceptor;
import android.util.Log;
import com.itbird.okhttpstudy.okhttp.Constants;
import com.itbird.okhttpstudy.okhttp.Request;
import com.itbird.okhttpstudy.okhttp.Response;
import java.io.IOException;
/**
 * Created by itbird on 2022/11/24
 */
public class ConnectInterceptor implements Interceptor {
    public ConnectInterceptor() {
    }
    @Override
    public Response intercept(Chain chain) throws IOException {
        Log.d(Constants.TAG, "ConnectInterceptor");
        Request request = chain.request();
        //表现为okhttp的话，这里就是socket简历连接，并且将socket输入输出流与okio绑定在一起
        return chain.proceed(request);
    }
}

CallServerInterceptor

package com.itbird.okhttpstudy.interceptor;
import android.util.Log;
import com.itbird.okhttpstudy.okhttp.Constants;
import com.itbird.okhttpstudy.okhttp.Request;
import com.itbird.okhttpstudy.okhttp.Response;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
/**
 * Created by itbird on 2022/11/24
 */
public class CallServerInterceptor implements Interceptor {
    public CallServerInterceptor() {
    }
    @Override
    public Response intercept(Chain chain) throws IOException {
        Log.d(Constants.TAG, "CallServerInterceptor");
        Request request = chain.request();
        try {
            //获取连接请求
            URL url = new URL(request.url());
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            //设置连接超时
            httpURLConnection.setConnectTimeout(3000);
            //设置方法
            httpURLConnection.setRequestMethod(request.method());
            if (request.requsetBody() != null) {
                httpURLConnection.setRequestProperty("Content-Type", request.requsetBody().getContentType());
                httpURLConnection.setRequestProperty("Content-Length", String.valueOf(request.requsetBody().getContentLength()));
                Log.d(Constants.TAG, httpURLConnection.getRequestProperty("Content-Length"));
                Log.d(Constants.TAG, httpURLConnection.getRequestProperty("Content-Type"));
            }
            //开始连接
            httpURLConnection.connect();
            //插入，如果requsetbody不为空，则继续写入内容
            if (request.requsetBody() != null) {
                request.requsetBody().writeBodyData(httpURLConnection.getOutputStream());
            }
            //判断返回的状态码
            if (httpURLConnection.getResponseCode() == 200) {
                //获取返回的数据
                InputStream inputStream = httpURLConnection.getInputStream();
                //将返回的数据，封装为response
                Response response = new Response(inputStream);
                return response;
            }
        } catch (MalformedURLException e) {
            throw e;
        } catch (IOException e) {
            throw e;
        }
        return null;
    }
}

运行一下

题外话

说到责任链模式，这里有一个题外话，我们之前分析view事件源码的时候，也看到过，view 事件源码，也是责任链机制，它是通过每层返回true、false来决定是否拦截。

大家想一下，和okhttp这里的责任链有啥不同的？我们上面查看okhttp源码的时候知道，它并不是通过每层返回true or false来决定是否拦截的，而是根据每层返回的response 以及 是否抛出异常来决定是否拦截。

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