Android教程網 >> Android技術 >> 關於Android編程 >> Android OkHttp完全解析是時候來了解OkHttp了

Android OkHttp完全解析是時候來了解OkHttp了

編輯：關於Android編程

一、概述

最近在群裡聽到各種討論okhttp的話題，可見okhttp的口碑相當好了。再加上Google貌似在6.0版本裡面刪除了HttpClient相關API，對於這個行為不做評價。為了更好的在應對網絡訪問，學習下okhttp還是蠻必要的，本篇博客首先介紹okhttp的簡單使用，主要包含：

一般的get請求
一般的post請求
基於Http的文件上傳
文件下載
加載圖片
支持請求回調，直接返回對象、對象集合
支持session的保持

最後會對上述幾個功能進行封裝，完整的封裝類的地址見：Android/okhttp-utils" target="_blank">https://github.com/hongyangAndroid/okhttp-utils

使用前，對於AndroidStudio的用戶，可以選擇添加:

compile 'com.squareup.okhttp:okhttp:2.4.0'

或者Eclipse的用戶，可以下載最新的jarokhttp he latest JAR，添加依賴就可以用了。

注意:okhttp內部依賴okio，別忘了同時導入okio：

gradle:compile 'com.squareup.okio:okio:1.5.0'

最新的jar地址：okio the latest JAR

二、使用教程

（一）Http Get

對了網絡加載庫，那麼最常見的肯定就是http get請求了，比如獲取一個網頁的內容。

//創建okHttpClient對象
OkHttpClient mOkHttpClient = new OkHttpClient();
//創建一個Request
final Request request = new Request.Builder()
                .url("https://github.com/hongyangAndroid")
                .build();
//new call
Call call = mOkHttpClient.newCall(request); 
//請求加入調度
call.enqueue(new Callback()
        {
            @Override
            public void onFailure(Request request, IOException e)
            {
            }

            @Override
            public void onResponse(final Response response) throws IOException
            {
                    //String htmlStr =  response.body().string();
            }
        });

以上就是發送一個get請求的步驟，首先構造一個Request對象，參數最起碼有個url，當然你可以通過Request.Builder設置更多的參數比如：header、method等。
然後通過request的對象去構造得到一個Call對象，類似於將你的請求封裝成了任務，既然是任務，就會有execute()和cancel()等方法。
最後，我們希望以異步的方式去執行請求，所以我們調用的是call.enqueue，將call加入調度隊列，然後等待任務執行完成，我們在Callback中即可得到結果。

看到這，你會發現，整體的寫法還是比較長的，所以封裝肯定是要做的，不然每個請求這麼寫，得累死。

ok，需要注意幾點：

onResponse回調的參數是response，一般情況下，比如我們希望獲得返回的字符串，可以通過response.body().string()獲取；如果希望獲得返回的二進制字節數組，則調用response.body().bytes()；如果你想拿到返回的inputStream，則調用response.body().byteStream()

看到這，你可能會奇怪，竟然還能拿到返回的inputStream，看到這個最起碼能意識到一點，這裡支持大文件下載，有inputStream我們就可以通過IO的方式寫文件。不過也說明一個問題，這個onResponse執行的線程並不是UI線程。的確是的，如果你希望操作控件，還是需要使用handler等，例如：

@Override
public void onResponse(final Response response) throws IOException
{
      final String res = response.body().string();
      runOnUiThread(new Runnable()
      {
          @Override
          public void run()
          {
            mTv.setText(res);
          }

      });
}

我們這裡是異步的方式去執行，當然也支持阻塞的方式，上面我們也說了Call有一個execute()方法，你也可以直接調用call.execute()通過返回一個Response。

(二) Http Post 攜帶參數

看來上面的簡單的get請求，基本上整個的用法也就掌握了，比如post攜帶參數，也僅僅是Request的構造的不同。

Request request = buildMultipartFormRequest(
        url, new File[]{file}, new String[]{fileKey}, null);
FormEncodingBuilder builder = new FormEncodingBuilder();   
builder.add("username","張鴻洋");

Request request = new Request.Builder()
                   .url(url)
                .post(builder.build())
                .build();
 mOkHttpClient.newCall(request).enqueue(new Callback(){});

大家都清楚，post的時候，參數是包含在請求體中的；所以我們通過FormEncodingBuilder。添加多個String鍵值對，然後去構造RequestBody，最後完成我們Request的構造。

後面的就和上面一樣了。

（三）基於Http的文件上傳

接下來我們在介紹一個可以構造RequestBody的Builder，叫做MultipartBuilder。當我們需要做類似於表單上傳的時候，就可以使用它來構造我們的requestBody。

File file = new File(Environment.getExternalStorageDirectory(), "balabala.mp4");

RequestBody fileBody = RequestBody.create(MediaType.parse("application/octet-stream"), file);

RequestBody requestBody = new MultipartBuilder()
     .type(MultipartBuilder.FORM)
     .addPart(Headers.of(
          "Content-Disposition", 
              "form-data; name=\"username\""), 
          RequestBody.create(null, "張鴻洋"))
     .addPart(Headers.of(
         "Content-Disposition", 
         "form-data; name=\"mFile\"; 
         filename=\"wjd.mp4\""), fileBody)
     .build();

Request request = new Request.Builder()
    .url("http://192.168.1.103:8080/okHttpServer/fileUpload")
    .post(requestBody)
    .build();

Call call = mOkHttpClient.newCall(request);
call.enqueue(new Callback()
{
    //...
});

上述代碼向服務器傳遞了一個鍵值對username:張鴻洋和一個文件。我們通過MultipartBuilder的addPart方法可以添加鍵值對或者文件。

其實類似於我們拼接模擬浏覽器行為的方式，如果你對這塊不了解，可以參考：從原理角度解析Android （Java） http 文件上傳

ok，對於我們最開始的目錄還剩下圖片下載，文件下載；這兩個一個是通過回調的Response拿到byte[]然後decode成圖片；文件下載，就是拿到inputStream做寫文件操作，我們這裡就不贅述了。

關於用法，也可以參考泡網OkHttp使用教程

接下來我們主要看如何封裝上述的代碼。

三、封裝

由於按照上述的代碼，寫多個請求肯定包含大量的重復代碼，所以我希望封裝後的代碼調用是這樣的：

（一）使用

一般的get請求

 OkHttpClientManager.getAsyn("https://www.baidu.com", new OkHttpClientManager.ResultCallback()
        {
            @Override
            public void onError(Request request, Exception e)
            {
                e.printStackTrace();
            }

            @Override
            public void onResponse(String u)
            {
                mTv.setText(u);//注意這裡是UI線程
            }
        });

對於一般的請求，我們希望給個url，然後CallBack裡面直接操作控件。

文件上傳且攜帶參數

我們希望提供一個方法，傳入url,params,file,callback即可。

  OkHttpClientManager.postAsyn("http://192.168.1.103:8080/okHttpServer/fileUpload",//
    new OkHttpClientManager.ResultCallback()
    {
        @Override
        public void onError(Request request, IOException e)
        {
            e.printStackTrace();
        }

        @Override
        public void onResponse(String result)
        {

        }
    },//
    file,//
    "mFile",//
    new OkHttpClientManager.Param[]{
            new OkHttpClientManager.Param("username", "zhy"),
            new OkHttpClientManager.Param("password", "123")}
        );

鍵值對沒什麼說的，參數3為file，參數4為file對應的name，這個name不是文件的名字對應的是name後面的值，即mFile.

文件下載

對於文件下載，提供url，目標dir，callback即可。

OkHttpClientManager.downloadAsyn(
    "http://192.168.1.103:8080/okHttpServer/files/messenger_01.png",    
    Environment.getExternalStorageDirectory().getAbsolutePath(), 
new OkHttpClientManager.ResultCallback()
    {
        @Override
        public void onError(Request request, IOException e)
        {

        }

        @Override
        public void onResponse(String response)
        {
            //文件下載成功，這裡回調的reponse為文件的absolutePath
        }
});

展示圖片

展示圖片，我們希望提供一個url和一個imageview，如果下載成功，直接幫我們設置上即可。

 OkHttpClientManager.displayImage(mImageView, 
     "http://images.csdn.net/20150817/1.jpg");

內部會自動根據imageview的大小自動對圖片進行合適的壓縮。雖然，這裡可能不適合一次性加載大量圖片的場景，但是對於app中偶爾有幾個圖片的加載，還是可用的。

四、整合Gson

很多人提出項目中使用時，服務端返回的是Json字符串，希望客戶端回調可以直接拿到對象，於是整合進入了Gson，完善該功能。

（一）直接回調對象

例如現在有個User實體類：

package com.zhy.utils.http.okhttp;

public class User {

    public String username ; 
    public String password  ;

    public User() {
        // TODO Auto-generated constructor stub
    }

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    @Override
    public String toString()
    {
        return "User{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

服務端返回：

{"username":"zhy","password":"123"}

客戶端可以如下方式調用：

 OkHttpClientManager.getAsyn("http://192.168.56.1:8080/okHttpServer/user!getUser",
new OkHttpClientManager.ResultCallback()
{
    @Override
    public void onError(Request request, Exception e)
    {
        e.printStackTrace();
    }

    @Override
    public void onResponse(User user)
    {
        mTv.setText(u.toString());//UI線程
    }
});

我們傳入泛型User，在onResponse裡面直接回調User對象。
這裡特別要注意的事，如果在json字符串->實體對象過程中發生錯誤，程序不會崩潰，onError方法會被回調。

注意：這裡做了少許的更新，接口命名從StringCallback修改為ResultCallback。接口中的onFailure方法修改為onError。

(二) 回調對象集合

依然是上述的User類，服務端返回

[{"username":"zhy","password":"123"},{"username":"lmj","password":"12345"}]

則客戶端可以如下調用：

OkHttpClientManager.getAsyn("http://192.168.56.1:8080/okHttpServer/user!getUsers",
new OkHttpClientManager.ResultCallback>()
{
    @Override
    public void onError(Request request, Exception e)
    {
        e.printStackTrace();
    }
    @Override
    public void onResponse(List us)
    {
        Log.e("TAG", us.size() + "");
        mTv.setText(us.get(1).toString());
    }
});

唯一的區別，就是泛型變為List，ok ，如果發現bug或者有任何意見歡迎留言。

源碼

ok，基本介紹完了，對於封裝的代碼其實也很簡單，我就直接貼出來了，因為也沒什麼好介紹的，如果你看完上面的用法，肯定可以看懂：

package com.zhy.utils.http.okhttp;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Looper;
import android.widget.ImageView;

import com.google.gson.Gson;
import com.google.gson.internal.$Gson$Types;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.FormEncodingBuilder;
import com.squareup.okhttp.Headers;
import com.squareup.okhttp.MediaType;
import com.squareup.okhttp.MultipartBuilder;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.RequestBody;
import com.squareup.okhttp.Response;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.net.CookieManager;
import java.net.CookiePolicy;
import java.net.FileNameMap;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * Created by zhy on 15/8/17.
 */
public class OkHttpClientManager
{
    private static OkHttpClientManager mInstance;
    private OkHttpClient mOkHttpClient;
    private Handler mDelivery;
    private Gson mGson;


    private static final String TAG = "OkHttpClientManager";

    private OkHttpClientManager()
    {
        mOkHttpClient = new OkHttpClient();
        //cookie enabled
        mOkHttpClient.setCookieHandler(new CookieManager(null, CookiePolicy.ACCEPT_ORIGINAL_SERVER));
        mDelivery = new Handler(Looper.getMainLooper());
        mGson = new Gson();
    }

    public static OkHttpClientManager getInstance()
    {
        if (mInstance == null)
        {
            synchronized (OkHttpClientManager.class)
            {
                if (mInstance == null)
                {
                    mInstance = new OkHttpClientManager();
                }
            }
        }
        return mInstance;
    }

    /**
     * 同步的Get請求
     *
     * @param url
     * @return Response
     */
    private Response _getAsyn(String url) throws IOException
    {
        final Request request = new Request.Builder()
                .url(url)
                .build();
        Call call = mOkHttpClient.newCall(request);
        Response execute = call.execute();
        return execute;
    }

    /**
     * 同步的Get請求
     *
     * @param url
     * @return 字符串
     */
    private String _getAsString(String url) throws IOException
    {
        Response execute = _getAsyn(url);
        return execute.body().string();
    }


    /**
     * 異步的get請求
     *
     * @param url
     * @param callback
     */
    private void _getAsyn(String url, final ResultCallback callback)
    {
        final Request request = new Request.Builder()
                .url(url)
                .build();
        deliveryResult(callback, request);
    }


    /**
     * 同步的Post請求
     *
     * @param url
     * @param params post的參數
     * @return
     */
    private Response _post(String url, Param... params) throws IOException
    {
        Request request = buildPostRequest(url, params);
        Response response = mOkHttpClient.newCall(request).execute();
        return response;
    }


    /**
     * 同步的Post請求
     *
     * @param url
     * @param params post的參數
     * @return 字符串
     */
    private String _postAsString(String url, Param... params) throws IOException
    {
        Response response = _post(url, params);
        return response.body().string();
    }

    /**
     * 異步的post請求
     *
     * @param url
     * @param callback
     * @param params
     */
    private void _postAsyn(String url, final ResultCallback callback, Param... params)
    {
        Request request = buildPostRequest(url, params);
        deliveryResult(callback, request);
    }

    /**
     * 異步的post請求
     *
     * @param url
     * @param callback
     * @param params
     */
    private void _postAsyn(String url, final ResultCallback callback, Map params)
    {
        Param[] paramsArr = map2Params(params);
        Request request = buildPostRequest(url, paramsArr);
        deliveryResult(callback, request);
    }

    /**
     * 同步基於post的文件上傳
     *
     * @param params
     * @return
     */
    private Response _post(String url, File[] files, String[] fileKeys, Param... params) throws IOException
    {
        Request request = buildMultipartFormRequest(url, files, fileKeys, params);
        return mOkHttpClient.newCall(request).execute();
    }

    private Response _post(String url, File file, String fileKey) throws IOException
    {
        Request request = buildMultipartFormRequest(url, new File[]{file}, new String[]{fileKey}, null);
        return mOkHttpClient.newCall(request).execute();
    }

    private Response _post(String url, File file, String fileKey, Param... params) throws IOException
    {
        Request request = buildMultipartFormRequest(url, new File[]{file}, new String[]{fileKey}, params);
        return mOkHttpClient.newCall(request).execute();
    }

    /**
     * 異步基於post的文件上傳
     *
     * @param url
     * @param callback
     * @param files
     * @param fileKeys
     * @throws IOException
     */
    private void _postAsyn(String url, ResultCallback callback, File[] files, String[] fileKeys, Param... params) throws IOException
    {
        Request request = buildMultipartFormRequest(url, files, fileKeys, params);
        deliveryResult(callback, request);
    }

    /**
     * 異步基於post的文件上傳，單文件不帶參數上傳
     *
     * @param url
     * @param callback
     * @param file
     * @param fileKey
     * @throws IOException
     */
    private void _postAsyn(String url, ResultCallback callback, File file, String fileKey) throws IOException
    {
        Request request = buildMultipartFormRequest(url, new File[]{file}, new String[]{fileKey}, null);
        deliveryResult(callback, request);
    }

    /**
     * 異步基於post的文件上傳，單文件且攜帶其他form參數上傳
     *
     * @param url
     * @param callback
     * @param file
     * @param fileKey
     * @param params
     * @throws IOException
     */
    private void _postAsyn(String url, ResultCallback callback, File file, String fileKey, Param... params) throws IOException
    {
        Request request = buildMultipartFormRequest(url, new File[]{file}, new String[]{fileKey}, params);
        deliveryResult(callback, request);
    }

    /**
     * 異步下載文件
     *
     * @param url
     * @param destFileDir 本地文件存儲的文件夾
     * @param callback
     */
    private void _downloadAsyn(final String url, final String destFileDir, final ResultCallback callback)
    {
        final Request request = new Request.Builder()
                .url(url)
                .build();
        final Call call = mOkHttpClient.newCall(request);
        call.enqueue(new Callback()
        {
            @Override
            public void onFailure(final Request request, final IOException e)
            {
                sendFailedStringCallback(request, e, callback);
            }

            @Override
            public void onResponse(Response response)
            {
                InputStream is = null;
                byte[] buf = new byte[2048];
                int len = 0;
                FileOutputStream fos = null;
                try
                {
                    is = response.body().byteStream();
                    File file = new File(destFileDir, getFileName(url));
                    fos = new FileOutputStream(file);
                    while ((len = is.read(buf)) != -1)
                    {
                        fos.write(buf, 0, len);
                    }
                    fos.flush();
                    //如果下載文件成功，第一個參數為文件的絕對路徑
                    sendSuccessResultCallback(file.getAbsolutePath(), callback);
                } catch (IOException e)
                {
                    sendFailedStringCallback(response.request(), e, callback);
                } finally
                {
                    try
                    {
                        if (is != null) is.close();
                    } catch (IOException e)
                    {
                    }
                    try
                    {
                        if (fos != null) fos.close();
                    } catch (IOException e)
                    {
                    }
                }

            }
        });
    }

    private String getFileName(String path)
    {
        int separatorIndex = path.lastIndexOf("/");
        return (separatorIndex < 0) ? path : path.substring(separatorIndex + 1, path.length());
    }

    /**
     * 加載圖片
     *
     * @param view
     * @param url
     * @throws IOException
     */
    private void _displayImage(final ImageView view, final String url, final int errorResId)
    {
        final Request request = new Request.Builder()
                .url(url)
                .build();
        Call call = mOkHttpClient.newCall(request);
        call.enqueue(new Callback()
        {
            @Override
            public void onFailure(Request request, IOException e)
            {
                setErrorResId(view, errorResId);
            }

            @Override
            public void onResponse(Response response)
            {
                InputStream is = null;
                try
                {
                    is = response.body().byteStream();
                    ImageUtils.ImageSize actualImageSize = ImageUtils.getImageSize(is);
                    ImageUtils.ImageSize imageViewSize = ImageUtils.getImageViewSize(view);
                    int inSampleSize = ImageUtils.calculateInSampleSize(actualImageSize, imageViewSize);
                    try
                    {
                        is.reset();
                    } catch (IOException e)
                    {
                        response = _getAsyn(url);
                        is = response.body().byteStream();
                    }

                    BitmapFactory.Options ops = new BitmapFactory.Options();
                    ops.inJustDecodeBounds = false;
                    ops.inSampleSize = inSampleSize;
                    final Bitmap bm = BitmapFactory.decodeStream(is, null, ops);
                    mDelivery.post(new Runnable()
                    {
                        @Override
                        public void run()
                        {
                            view.setImageBitmap(bm);
                        }
                    });
                } catch (Exception e)
                {
                    setErrorResId(view, errorResId);

                } finally
                {
                    if (is != null) try
                    {
                        is.close();
                    } catch (IOException e)
                    {
                        e.printStackTrace();
                    }
                }
            }
        });


    }

    private void setErrorResId(final ImageView view, final int errorResId)
    {
        mDelivery.post(new Runnable()
        {
            @Override
            public void run()
            {
                view.setImageResource(errorResId);
            }
        });
    }


    //*************對外公布的方法************


    public static Response getAsyn(String url) throws IOException
    {
        return getInstance()._getAsyn(url);
    }


    public static String getAsString(String url) throws IOException
    {
        return getInstance()._getAsString(url);
    }

    public static void getAsyn(String url, ResultCallback callback)
    {
        getInstance()._getAsyn(url, callback);
    }

    public static Response post(String url, Param... params) throws IOException
    {
        return getInstance()._post(url, params);
    }

    public static String postAsString(String url, Param... params) throws IOException
    {
        return getInstance()._postAsString(url, params);
    }

    public static void postAsyn(String url, final ResultCallback callback, Param... params)
    {
        getInstance()._postAsyn(url, callback, params);
    }


    public static void postAsyn(String url, final ResultCallback callback, Map params)
    {
        getInstance()._postAsyn(url, callback, params);
    }


    public static Response post(String url, File[] files, String[] fileKeys, Param... params) throws IOException
    {
        return getInstance()._post(url, files, fileKeys, params);
    }

    public static Response post(String url, File file, String fileKey) throws IOException
    {
        return getInstance()._post(url, file, fileKey);
    }

    public static Response post(String url, File file, String fileKey, Param... params) throws IOException
    {
        return getInstance()._post(url, file, fileKey, params);
    }

    public static void postAsyn(String url, ResultCallback callback, File[] files, String[] fileKeys, Param... params) throws IOException
    {
        getInstance()._postAsyn(url, callback, files, fileKeys, params);
    }


    public static void postAsyn(String url, ResultCallback callback, File file, String fileKey) throws IOException
    {
        getInstance()._postAsyn(url, callback, file, fileKey);
    }


    public static void postAsyn(String url, ResultCallback callback, File file, String fileKey, Param... params) throws IOException
    {
        getInstance()._postAsyn(url, callback, file, fileKey, params);
    }

    public static void displayImage(final ImageView view, String url, int errorResId) throws IOException
    {
        getInstance()._displayImage(view, url, errorResId);
    }


    public static void displayImage(final ImageView view, String url)
    {
        getInstance()._displayImage(view, url, -1);
    }

    public static void downloadAsyn(String url, String destDir, ResultCallback callback)
    {
        getInstance()._downloadAsyn(url, destDir, callback);
    }

    //****************************


    private Request buildMultipartFormRequest(String url, File[] files,
                                              String[] fileKeys, Param[] params)
    {
        params = validateParam(params);

        MultipartBuilder builder = new MultipartBuilder()
                .type(MultipartBuilder.FORM);

        for (Param param : params)
        {
            builder.addPart(Headers.of("Content-Disposition", "form-data; name=\"" + param.key + "\""),
                    RequestBody.create(null, param.value));
        }
        if (files != null)
        {
            RequestBody fileBody = null;
            for (int i = 0; i < files.length; i++)
            {
                File file = files[i];
                String fileName = file.getName();
                fileBody = RequestBody.create(MediaType.parse(guessMimeType(fileName)), file);
                //TODO 根據文件名設置contentType
                builder.addPart(Headers.of("Content-Disposition",
                                "form-data; name=\"" + fileKeys[i] + "\"; filename=\"" + fileName + "\""),
                        fileBody);
            }
        }

        RequestBody requestBody = builder.build();
        return new Request.Builder()
                .url(url)
                .post(requestBody)
                .build();
    }

    private String guessMimeType(String path)
    {
        FileNameMap fileNameMap = URLConnection.getFileNameMap();
        String contentTypeFor = fileNameMap.getContentTypeFor(path);
        if (contentTypeFor == null)
        {
            contentTypeFor = "application/octet-stream";
        }
        return contentTypeFor;
    }


    private Param[] validateParam(Param[] params)
    {
        if (params == null)
            return new Param[0];
        else return params;
    }

    private Param[] map2Params(Map params)
    {
        if (params == null) return new Param[0];
        int size = params.size();
        Param[] res = new Param[size];
        Set> entries = params.entrySet();
        int i = 0;
        for (Map.Entry entry : entries)
        {
            res[i++] = new Param(entry.getKey(), entry.getValue());
        }
        return res;
    }

    private static final String SESSION_KEY = "Set-Cookie";
    private static final String mSessionKey = "JSESSIONID";

    private Map mSessions = new HashMap();

    private void deliveryResult(final ResultCallback callback, Request request)
    {
        mOkHttpClient.newCall(request).enqueue(new Callback()
        {
            @Override
            public void onFailure(final Request request, final IOException e)
            {
                sendFailedStringCallback(request, e, callback);
            }

            @Override
            public void onResponse(final Response response)
            {
                try
                {
                    final String string = response.body().string();
                    if (callback.mType == String.class)
                    {
                        sendSuccessResultCallback(string, callback);
                    } else
                    {
                        Object o = mGson.fromJson(string, callback.mType);
                        sendSuccessResultCallback(o, callback);
                    }


                } catch (IOException e)
                {
                    sendFailedStringCallback(response.request(), e, callback);
                } catch (com.google.gson.JsonParseException e)//Json解析的錯誤
                {
                    sendFailedStringCallback(response.request(), e, callback);
                }

            }
        });
    }

    private void sendFailedStringCallback(final Request request, final Exception e, final ResultCallback callback)
    {
        mDelivery.post(new Runnable()
        {
            @Override
            public void run()
            {
                if (callback != null)
                    callback.onError(request, e);
            }
        });
    }

    private void sendSuccessResultCallback(final Object object, final ResultCallback callback)
    {
        mDelivery.post(new Runnable()
        {
            @Override
            public void run()
            {
                if (callback != null)
                {
                    callback.onResponse(object);
                }
            }
        });
    }

    private Request buildPostRequest(String url, Param[] params)
    {
        if (params == null)
        {
            params = new Param[0];
        }
        FormEncodingBuilder builder = new FormEncodingBuilder();
        for (Param param : params)
        {
            builder.add(param.key, param.value);
        }
        RequestBody requestBody = builder.build();
        return new Request.Builder()
                .url(url)
                .post(requestBody)
                .build();
    }


    public static abstract class ResultCallback
    {
        Type mType;

        public ResultCallback()
        {
            mType = getSuperclassTypeParameter(getClass());
        }

        static Type getSuperclassTypeParameter(Class subclass)
        {
            Type superclass = subclass.getGenericSuperclass();
            if (superclass instanceof Class)
            {
                throw new RuntimeException("Missing type parameter.");
            }
            ParameterizedType parameterized = (ParameterizedType) superclass;
            return $Gson$Types.canonicalize(parameterized.getActualTypeArguments()[0]);
        }

        public abstract void onError(Request request, Exception e);

        public abstract void onResponse(T response);
    }

    public static class Param
    {
        public Param()
        {
        }

        public Param(String key, String value)
        {
            this.key = key;
            this.value = value;
        }

        String key;
        String value;
    }


}