Android 網路框架 OKHttp 學習

OKHttp

okHttp: OKHttp是Android版Http客戶端。非常高效，支援SPDY、連線池、GZIP和 HTTP 快取。預設情況下，OKHttp會自動處理常見的網路問題，像二次連線、SSL的握手問題。如果你的應用程式中整合了OKHttp，Retrofit預設會使用OKHttp處理其他網路層請求。

An HTTP & SPDY client for Android and Java applications 從Android4.4開始HttpURLConnection的底層實現採用的是okHttp.

使用要求:對於Android：2.3以上，對於Java:java7以上 兩個模組： okhttp-urlconnection實現.HttpURLConnection API； okhttp-apache實現Apache HttpClient API. 依賴：okio(https://github.com/square/okio): Okio, which OkHttp uses for fast I/O and resizable buffers.

安裝：

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());
  }

非同步GET:

在一個工作執行緒中下載檔案，當響應可讀時回撥Callback介面。讀取響應時會阻塞當前執行緒。OkHttp現階段不提供非同步api來接收響應體。

  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());
      }
    });
  }

訪問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：

為了快取響應，你需要一個你可以讀寫的快取目錄，和快取大小的限制。這個快取目錄應該是私有的，不信任的程式應不能讀取快取內容。

一個快取目錄同時擁有多個快取訪問是錯誤的。大多數程式只需要呼叫一次 new OkHttp() ，在第一次呼叫時配置好快取，然後其他地方只需要呼叫這個例項就可以了。否則兩個快取示例互相干擾，破壞響應快取，而且有可能會導致程式崩潰。

響應快取使用HTTP頭作為配置。你可以在請求頭中新增 Cache-Control: max-stale=3600 ,OkHTTP快取會支援。你的服務通過響應頭確定響應快取多長時間，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());
  }

為避免當驗證失敗時多次重試，我們可以通過返回null來放棄驗證：

 if (responseCount(response) >= 3) {
    return null; // If we've failed 3 times, give up.
  }
//新增以下方法
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());