經過一段時間的掙扎，終於把新公司專案的網路框架換成了retrofit，由於專案是有失敗重試和重定向需求的，所以需要在新的網路框架上增加這個功能，大家都知道retrofit的網路請求部分是基於okhttp的。這個時候可愛的Interceptor設計就提現出他的好處了，不需要修改其他的程式碼，直接增加一個攔截器就OK了

實現一個攔截器繼承Interceptor（2.0到3.0之前的版本）

public class RetryAndChangeIpInterceptor implements Interceptor {
    String FirstIP;
    String SecondIP;
    int
 
 RetryCount;

    public RetryAndChangeIpInterceptor(String firsrIP, String secondIP, int tryCount) {
        FirstIP = firsrIP;
        SecondIP = secondIP;
        RetryCount = tryCount;
    }

    public RetryAndChangeIpInterceptor(String firsrIP, String secondIP) {
        FirstIP = firsrIP;
        SecondIP = secondIP;
        RetryCount = 3
 
;
    }

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        // try the request
        Response response = chain.proceed(request);
        int tryCount = 0;
        while (!response.isSuccessful() && tryCount <= RetryCount) {
            String url = request.url().toString();
            if
 
 (!Util.checkNULL(FirstIP) && !Util.checkNULL(SecondIP)) {//重定向
                if (url.contains(FirstIP)) {
                    url = url.replace(FirstIP, SecondIP);
                } else if (url.contains(SecondIP)) {
                    url = url.replace(SecondIP, FirstIP);
                }
                Request newRequest = response.request().newBuilder().url(url).build();
                Log.d("intercept", "Request is not successful - " + tryCount);
                tryCount++;
                // retry the request
                response = chain.proceed(newRequest);
            } else {
                response = chain.proceed(request);
            }
        }
        return response;
    }
}

3.0及以上版本（取消了httpEngine，採用了純攔截器遞迴呼叫機制）

package com.sunshine.retrofit.interceptor;

import android.util.Log;


import java.io.IOException;
import java.util.List;

import okhttp3.Interceptor;
import okhttp3.Request;
import okhttp3.Response;

/**
 * Created by 耿 on 2016/8/12.
 */
public class RetryAndChangeIpInterceptor implements Interceptor {
    int RetryCount = 3;
    String FirstIP;
    List<String> SERVERS;

    public RetryAndChangeIpInterceptor(String firsrIP, List<String> sERVERS) {
        FirstIP = firsrIP;
        SERVERS = sERVERS;
        RetryCount = 3;
    }

    public RetryAndChangeIpInterceptor(String firsrIP, List<String> sERVERS, int tryCount) {
        FirstIP = firsrIP;
        SERVERS = sERVERS;
        RetryCount = tryCount;
    }

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        // try the request
        Response response = doRequest(chain, request);
        int tryCount = 0;
        String url = request.url().toString();
        while (response == null && tryCount <= RetryCount) {
            url = switchServer(url);
            Request newRequest = request.newBuilder().url(url).build();
            Log.d("intercept", "Request is not successful - " + tryCount);
            tryCount++;
            // retry the request
            response = doRequest(chain, newRequest);
        }
        if (response == null) {
            throw new IOException();
        }
        return response;
    }

    private Response doRequest(Chain chain, Request request) {
        Response response = null;
        try {
            response = chain.proceed(request);
        } catch (Exception e) {
        }
        return response;
    }

    private String switchServer(String url) {
        String newUrlString = url;
        if (url.contains(FirstIP)) {
            for (String server : SERVERS) {
                if (!FirstIP.equals(server)) {
                    newUrlString = url.replace(FirstIP, server);
                    break;
                }
            }
        } else {
            for (String server : SERVERS) {
                if (url.contains(server)) {
                    newUrlString = url.replace(server, FirstIP);
                    break;
                }
            }
        }
        return newUrlString;
    }


}

配置OkHttpClient

  OkHttpClient client = new OkHttpClient.Builder()
                    .addInterceptor(new RetryAndChangeIpInterceptor(BASE_URL, SecondIP))//新增失敗重試及重定向攔截器

                    .retryOnConnectionFailure(true)//允許失敗重試
                    .connectTimeout(8, TimeUnit.SECONDS)
                    .readTimeout(5, TimeUnit.SECONDS)
                    .writeTimeout(5, TimeUnit.SECONDS)
                    .build();

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