Http请求框架 okHttp 简单使用介绍

（今天接触了Http请求框架，搜索了一篇关于okHttp框架的博文，在此备份。）

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：okHttp

maven:（没有试过）

  com.squareup.okhttp
  okhttp
  2.3 . 0

Gradle:

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

（在gradle配置文件中附上这一句后点击Sync project with gradle files按钮，如下图。gradle会自动下载并安装相应jar包）

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());