OKHTTP

okHttp: OKHttp是Android版Http客户端。非常高效，支持SPDY、连接池、GZIP和 HTTP 缓存。默认情况下，OKHttp会自动处理常见的网络问题，像二次连接、SSL的握手问题。如果你的应用程序中集成了OKHttp，Retrofit默认会使用OKHttp处理其他网络层请求。
An HTTP & SPDY client for Android and Java applications 从Android4.4开始HttpURLConnection的底层实现采用的是okHttp.
使用要求:对于Android：2.3以上，对于Java:java7以上 两个模块： okhttp-urlconnection实现.HttpURLConnection API； okhttp-apache实现Apache HttpClient API. 依赖：okio(https://github.com/square/okio): Okio, which OkHttp uses for fast I/O and resizable buffers.

安装：

maven:

com.squareup.okhttpokhttp2.3.0

Gradle:

compile 'com.squareup.okhttp:okhttp:2.3.0'

GET A URL

同步GET:

  private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      Request request = new Request.Builder()          .url(http://publicobject.com/helloworld.txt)          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        Headers responseHeaders = response.headers();      for (int i = 0; i < responseHeaders.size(); i++) {        System.out.println(responseHeaders.name(i) + :  + responseHeaders.value(i));      }        System.out.println(response.body().string());    }

异步GET:

在一个工作线程中下载文件，当响应可读时回调Callback接口。读取响应时会阻塞当前线程。OkHttp现阶段不提供异步api来接收响应体。

  private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      Request request = new Request.Builder()          .url(http://publicobject.com/helloworld.txt)          .build();        client.newCall(request).enqueue(new Callback() {        @Override public void onFailure(Request request, Throwable throwable) {          throwable.printStackTrace();        }          @Override public void onResponse(Response response) throws IOException {          if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);            Headers responseHeaders = response.headers();          for (int i = 0; i < responseHeaders.size(); i++) {            System.out.println(responseHeaders.name(i) + :  + responseHeaders.value(i));          }            System.out.println(response.body().string());        }      });    }

访问Header:

  private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      Request request = new Request.Builder()          .url(https://api.github.com/repos/square/okhttp/issues)          .header(User-Agent, OkHttp Headers.java)          .addHeader(Accept, application/json; q=0.5)          .addHeader(Accept, application/vnd.github.v3+json)          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        System.out.println(Server:  + response.header(Server));      System.out.println(Date:  + response.header(Date));      System.out.println(Vary:  + response.headers(Vary));    }

POST TO A SERVER

Posting a String:

public static final MediaType jsonReq      = MediaType.parse(application/json; charset=utf-8);    OkHttpClient client = new OkHttpClient();    String post(String url, String json) throws IOException {    RequestBody body = RequestBody.create(jsonReq, json);    Request request = new Request.Builder()        .url(url)        .post(body)        .build();    Response response = client.newCall(request).execute();    return response.body().string();  }

Posting Streaming:

 public static final MediaType MEDIA_TYPE_MARKDOWN        = MediaType.parse(text/x-markdown; charset=utf-8);      private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      RequestBody requestBody = new RequestBody() {        @Override public MediaType contentType() {          return MEDIA_TYPE_MARKDOWN;        }          @Override public void writeTo(BufferedSink sink) throws IOException {          sink.writeUtf8(Numbers  );          sink.writeUtf8(-------  );          for (int i = 2; i <= 997; i++) {            sink.writeUtf8(String.format( * %s = %s  , i, factor(i)));          }        }          private String factor(int n) {          for (int i = 2; i < n; i++) {            int x = n / i;            if (x * i == n) return factor(x) +  ×  + i;          }          return Integer.toString(n);        }      };        Request request = new Request.Builder()          .url(https://api.github.com/markdown/raw)          .post(requestBody)          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        System.out.println(response.body().string());    }

Posting a File:

 public static final MediaType MEDIA_TYPE_MARKDOWN        = MediaType.parse(text/x-markdown; charset=utf-8);      private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      File file = new File(README.md);        Request request = new Request.Builder()          .url(https://api.github.com/markdown/raw)          .post(RequestBody.create(MEDIA_TYPE_MARKDOWN, file))          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        System.out.println(response.body().string());    }

Posting from parameters:

private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      RequestBody formBody = new FormEncodingBuilder()          .add(search, Jurassic Park)          .build();      Request request = new Request.Builder()          .url(https://en.wikipedia.org/w/index.php)          .post(formBody)          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        System.out.println(response.body().string());    }

Posting a multipart request:

 private static final String IMGUR_CLIENT_ID = ...;    private static final MediaType MEDIA_TYPE_PNG = MediaType.parse(image/png);      private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      // Use the imgur image upload API as documented at https://api.imgur.com/endpoints/image      RequestBody requestBody = new MultipartBuilder()          .type(MultipartBuilder.FORM)          .addPart(              Headers.of(Content-Disposition, form-data; name= itle),              RequestBody.create(null, Square Logo))          .addPart(              Headers.of(Content-Disposition, form-data; name=image),              RequestBody.create(MEDIA_TYPE_PNG, new File(website/static/logo-square.png)))          .build();        Request request = new Request.Builder()          .header(Authorization, Client-ID  + IMGUR_CLIENT_ID)          .url(https://api.imgur.com/3/image)          .post(requestBody)          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        System.out.println(response.body().string());    }

Posing Json with Gson

 private final OkHttpClient client = new OkHttpClient();    private final Gson gson = new Gson();      public void run() throws Exception {      Request request = new Request.Builder()          .url(https://api.github.com/gists/c2a7c39532239ff261be)          .build();      Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        Gist gist = gson.fromJson(response.body().charStream(), Gist.class);      for (Map.Entry entry : gist.files.entrySet()) {        System.out.println(entry.getKey());        System.out.println(entry.getValue().content);      }    }      static class Gist {      Map files;    }      static class GistFile {      String content;    }

Response Caching：

为了缓存响应，你需要一个你可以读写的缓存目录，和缓存大小的限制。这个缓存目录应该是私有的，不信任的程序应不能读取缓存内容。
一个缓存目录同时拥有多个缓存访问是错误的。大多数程序只需要调用一次 new OkHttp() ，在第一次调用时配置好缓存，然后其他地方只需要调用这个实例就可以了。否则两个缓存示例互相干扰，破坏响应缓存，而且有可能会导致程序崩溃。
响应缓存使用HTTP头作为配置。你可以在请求头中添加 Cache-Control: max-stale=3600 ,OkHttp缓存会支持。你的服务通过响应头确定响应缓存多长时间，例如使用 Cache-Control: max-age=9600 。

private final OkHttpClient client;      public CacheResponse(File cacheDirectory) throws Exception {      int cacheSize = 10 * 1024 * 1024; // 10 MiB      Cache cache = new Cache(cacheDirectory, cacheSize);        client = new OkHttpClient();      client.setCache(cache);    }      public void run() throws Exception {      Request request = new Request.Builder()          .url(http://publicobject.com/helloworld.txt)          .build();        Response response1 = client.newCall(request).execute();      if (!response1.isSuccessful()) throw new IOException(Unexpected code  + response1);        String response1Body = response1.body().string();      System.out.println(Response 1 response:           + response1);      System.out.println(Response 1 cache response:     + response1.cacheResponse());      System.out.println(Response 1 network response:   + response1.networkResponse());    }

Canceling a Call

    final Call call = client.newCall(request);          call.cancel();

Timeouts:

private final OkHttpClient client;      public ConfigureTimeouts() throws Exception {      client = new OkHttpClient();      client.setConnectTimeout(10, TimeUnit.SECONDS);      client.setWriteTimeout(10, TimeUnit.SECONDS);      client.setReadTimeout(30, TimeUnit.SECONDS);    }

Handling Authentication:

private final OkHttpClient client = new OkHttpClient();      public void run() throws Exception {      client.setAuthenticator(new Authenticator() {        @Override public Request authenticate(Proxy proxy, Response response) {          System.out.println(Authenticating for response:  + response);          System.out.println(Challenges:  + response.challenges());          String credential = Credentials.basic(jesse, password1);          return response.request().newBuilder()              .header(Authorization, credential)              .build();        }          @Override public Request authenticateProxy(Proxy proxy, Response response) {          return null; // Null indicates no attempt to authenticate.        }      });        Request request = new Request.Builder()          .url(http://publicobject.com/secrets/hellosecret.txt)          .build();        Response response = client.newCall(request).execute();      if (!response.isSuccessful()) throw new IOException(Unexpected code  + response);        System.out.println(response.body().string());    }

为避免当验证失败时多次重试，我们可以通过返回null来放弃验证：

 if (responseCount(response) >= 3) {      return null; // If we've failed 3 times, give up.    }  //添加以下方法  private int responseCount(Response response) {      int result = 1;      while ((response = response.priorResponse()) != null) {        result++;      }      return result;    }

Interceptors

class LoggingInterceptor implements Interceptor {    @Override public Response intercept(Chain chain) throws IOException {      Request request = chain.request();        long t1 = System.nanoTime();      logger.info(String.format(Sending request %s on %s%n%s,          request.url(), chain.connection(), request.headers()));        Response response = chain.proceed(request);        long t2 = System.nanoTime();      logger.info(String.format(Received response for %s in %.1fms%n%s,          response.request().url(), (t2 - t1) / 1e6d, response.headers()));        return response;    }  }

Application Interceptors：

OkHttpClient client = new OkHttpClient();  client.interceptors().add(new LoggingInterceptor());

Network Interceptors

OkHttpClient client = new OkHttpClient();  client.networkInterceptors().add(new LoggingInterceptor());