Android OkHttp完全解析
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一、概述
最近在群里听到各种讨论okhttp的话题，可见okhttp的口碑相当好了。再加上Google貌似在6.0版本里面删除了HttpClient相关API，对于这个行为不做评价。为了更好的在应对网络访问，学习下okhttp还是蛮必要的，本篇博客首先介绍okhttp的简单使用，主要包含：
一般的get请求
一般的post请求
基于Http的文件上传
文件下载
加载图片
支持请求回调，直接返回对象、对象集合
支持session的保持
最后会对上述几个功能进行封装，完整的封装类的地址见：https://github.com/hongyangAndroid/okhttp-utils
使用前，对于Android Studio的用户，可以选择添加:
compile 'com.squareup.okhttp:okhttp:2.4.0'或者Eclipse的用户，可以下载最新的jar okhttp he latest JAR ，添加依赖就可以用了。
注意:okhttp内部依赖okio，别忘了同时导入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
对了网络加载库，那么最常见的肯定就是http get请求了，比如获取一个网页的内容。
//创建okHttpClient对象OkHttpClient mOkHttpClient = new OkHttpClient();//创建一个Requestfinal Request request = new Request.Builder() .url("https://github.com/hongyangAndroid") .build();//new callCall call = mOkHttpClient.newCall(request); //请求加入调度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(); } }); - 以上就是发送一个get请求的步骤，首先构造一个Request对象，参数最起码有个url，当然你可以通过Request.Builder设置更多的参数比如：header、method等。
- 然后通过request的对象去构造得到一个Call对象，类似于将你的请求封装成了任务，既然是任务，就会有execute()和cancel()等方法。
- 最后，我们希望以异步的方式去执行请求，所以我们调用的是call.enqueue，将call加入调度队列，然后等待任务执行完成，我们在Callback中即可得到结果。
看到这，你会发现，整体的写法还是比较长的，所以封装肯定是要做的，不然每个请求这么写，得累死。
ok，需要注意几点：
- onResponse回调的参数是response，一般情况下，比如我们希望获得返回的字符串，可以通过response.body().string()获取；如果希望获得返回的二进制字节数组，则调用response.body().bytes()；如果你想拿到返回的inputStream，则调用response.body().byteStream()
看到这，你可能会奇怪，竟然还能拿到返回的inputStream，看到这个最起码能意识到一点，这里支持大文件下载，有inputStream我们就可以通过IO的方式写文件。不过也说明一个问题，这个onResponse执行的线程并不是UI线程。的确是的，如果你希望操作控件，还是需要使用handler等，例如：
@Overridepublic void onResponse(final Response response) throws IOException{ final String res = response.body().string(); runOnUiThread(new Runnable() { @Override public void run() { mTv.setText(res); } });}- 我们这里是异步的方式去执行，当然也支持阻塞的方式，上面我们也说了Call有一个execute()方法，你也可以直接调用call.execute()通过返回一个Response。
(二) Http Post 携带参数
看来上面的简单的get请求，基本上整个的用法也就掌握了，比如post携带参数，也仅仅是Request的构造的不同。
Request request = buildMultipartFormRequest( url, new File[]{file}, new String[]{fileKey}, null);FormEncodingBuilder builder = new FormEncodingBuilder(); builder.add("username","张三");Request request = new Request.Builder() .url(url) .post(builder.build()) .build(); mOkHttpClient.newCall(request).enqueue(new Callback(){});大家都清楚，post的时候，参数是包含在请求体中的；所以我们通过FormEncodingBuilder。添加多个String键值对，然后去构造RequestBody，最后完成我们Request的构造。
后面的就和上面一样了。
（三）基于Http的文件上传
接下来我们在介绍一个可以构造RequestBody的Builder，叫做MultipartBuilder。当我们需要做类似于表单上传的时候，就可以使用它来构造我们的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, "张鸿洋")) .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(){ //...});上述代码向服务器传递了一个键值对username:张鸿洋和一个文件。我们通过MultipartBuilder的addPart方法可以添加键值对或者文件。
其实类似于我们拼接模拟浏览器行为的方式，如果你对这块不了解，可以参考：从原理角度解析Android （Java） http 文件上传
ok，对于我们最开始的目录还剩下图片下载，文件下载；这两个一个是通过回调的Response拿到byte[]然后decode成图片；文件下载，就是拿到inputStream做写文件操作，我们这里就不赘述了。
关于用法，也可以参考泡网OkHttp使用教程
接下来我们主要看如何封装上述的代码。
三、封装
由于按照上述的代码，写多个请求肯定包含大量的重复代码，所以我希望封装后的代码调用是这样的：
（一）使用
- 一般的get请求
OkHttpClientManager.getAsyn("https://www.baidu.com", new OkHttpClientManager.ResultCallback<String>() { @Override public void onError(Request request, Exception e) { e.printStackTrace(); } @Override public void onResponse(String u) { mTv.setText(u);//注意这里是UI线程 } });对于一般的请求，我们希望给个url，然后CallBack里面直接操作控件。
2.文件上传且携带参数
我们希望提供一个方法，传入url,params,file,callback即可。
OkHttpClientManager.postAsyn("http://192.168.1.103:8080/okHttpServer/fileUpload",// new OkHttpClientManager.ResultCallback<String>() { @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")} );键值对没什么说的，参数3为file，参数4为file对应的name，这个name不是文件的名字；
对应于http中的
<input type="file" name="mFile" >对应的是name后面的值，即mFile.
3.文件下载
对于文件下载，提供url，目标dir，callback即可。
OkHttpClientManager.downloadAsyn( "http://192.168.1.103:8080/okHttpServer/files/messenger_01.png", Environment.getExternalStorageDirectory().getAbsolutePath(), new OkHttpClientManager.ResultCallback<String>() { @Override public void onError(Request request, IOException e) { } @Override public void onResponse(String response) { //文件下载成功，这里回调的reponse为文件的absolutePath }});4.展示图片
展示图片，我们希望提供一个url和一个imageview，如果下载成功，直接帮我们设置上即可。
OkHttpClientManager.displayImage(mImageView, "http://images.csdn.net/20150817/1.jpg");内部会自动根据imageview的大小自动对图片进行合适的压缩。虽然，这里可能不适合一次性加载大量图片的场景，但是对于app中偶尔有几个图片的加载，还是可用的。
四、整合Gson
很多人提出项目中使用时，服务端返回的是Json字符串，希望客户端回调可以直接拿到对象，于是整合进入了Gson，完善该功能。
（一）直接回调对象
例如现在有个User实体类：
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 + '\'' + '}'; }}服务端返回：
{"username":"zhy","password":"123"}客户端可以如下方式调用：
OkHttpClientManager.getAsyn("http://192.168.56.1:8080/okHttpServer/user!getUser",new OkHttpClientManager.ResultCallback<User>(){ @Override public void onError(Request request, Exception e) { e.printStackTrace(); } @Override public void onResponse(User user) { mTv.setText(u.toString());//UI线程 }});我们传入泛型User，在onResponse里面直接回调User对象。
这里特别要注意的事，如果在json字符串->实体对象过程中发生错误，程序不会崩溃，onError方法会被回调。
注意：这里做了少许的更新，接口命名从StringCallback修改为ResultCallback。接口中的onFailure方法修改为onError。
(二) 回调对象集合
依然是上述的User类，服务端返回
[{"username":"zhy","password":"123"},{"username":"lmj","password":"12345"}]则客户端可以如下调用：
OkHttpClientManager.getAsyn("http://192.168.56.1:8080/okHttpServer/user!getUsers",new OkHttpClientManager.ResultCallback<List<User>>(){ @Override public void onError(Request request, Exception e) { e.printStackTrace(); } @Override public void onResponse(List<User> us) { Log.e("TAG", us.size() + ""); mTv.setText(us.get(1).toString()); }});唯一的区别，就是泛型变为List ，ok ， 如果发现bug或者有任何意见欢迎留言。
源码
ok，基本介绍完了，对于封装的代码其实也很简单，我就直接贴出来了，因为也没什么好介绍的，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请求 * * @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请求 * * @param url * @return 字符串 */ private String _getAsString(String url) throws IOException { Response execute = _getAsyn(url); return execute.body().string(); } /** * 异步的get请求 * * @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请求 * * @param url * @param params post的参数 * @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请求 * * @param url * @param params post的参数 * @return 字符串 */ private String _postAsString(String url, Param... params) throws IOException { Response response = _post(url, params); return response.body().string(); } /** * 异步的post请求 * * @param url * @param callback * @param params */ private void _postAsyn(String url, final ResultCallback callback, Param... params) { Request request = buildPostRequest(url, params); deliveryResult(callback, request); } /** * 异步的post请求 * * @param url * @param callback * @param params */ private void _postAsyn(String url, final ResultCallback callback, Map<String, String> params) { Param[] paramsArr = map2Params(params); Request request = buildPostRequest(url, paramsArr); deliveryResult(callback, request); } /** * 同步基于post的文件上传 * * @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(); } /** * 异步基于post的文件上传 * * @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); } /** * 异步基于post的文件上传，单文件不带参数上传 * * @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); } /** * 异步基于post的文件上传，单文件且携带其他form参数上传 * * @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); } /** * 异步下载文件 * * @param url * @param destFileDir 本地文件存储的文件夹 * @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(); //如果下载文件成功，第一个参数为文件的绝对路径 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()); } /** * 加载图片 * * @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); } }); } //*************对外公布的方法************ 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<String, String> 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 根据文件名设置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<String, String> params) { if (params == null) return new Param[0]; int size = params.size(); Param[] res = new Param[size]; Set<Map.Entry<String, String>> entries = params.entrySet(); int i = 0; for (Map.Entry<String, String> 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<String, String> mSessions = new HashMap<String, String>(); 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解析的错误 { 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<T> { 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; }}源码地址okhttp-utils，大家可以自己下载查看。
参考文章
- https://github.com/square/okhttp
- http://square.github.io/okhttp/
- 泡网OkHttp使用教程
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