OkHttp整理

导入

compile 'com.squareup.okhttp3:okhttp:3.8.1'

混淆：

-dontwarn okio.**-dontwarn javax.annotation.Nullable-dontwarn javax.annotation.ParametersAreNonnullByDefault

最新版本请看github

使用示例：

同步Get

response.body().string()对于小文件来说很方便，但是如果文件大小大于1MB的话，尽量避免使用response.body().string()，因为这会把这个文件都加载到内存当中，应该使用流来读取比较好。

  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

在一个子线程进行下载，有response的时候才触发回调。回调在response的headers可用的时候触发，但是读取response的body还是可能会阻塞住。OkHttp当前不提供异步API来分部分接收response的body。

  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(Call call, IOException e) {        e.printStackTrace();      }      @Override public void onResponse(Call call, Response response) throws IOException {        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);        Headers responseHeaders = response.headers();        for (int i = 0, size = responseHeaders.size(); i < size; i++) {          System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));        }        System.out.println(response.body().string());      }    });  }

headers的获取

Http的headers一般是类似Map<String, String>的结构，即每个header字段对应着一个或者零个值。不过也存在一个header对应多个值的情况。

编写请求headers的时候，如果是一对一形式，则调用header(name, value)来设置，也就是旧值会覆盖新值；如果是一对多形式，则调用addHeader(name, value)。

读取响应的headers的时候，调用header(name)来获取该键名对应的最后一个值，如果没有就返回null。如果要返回该键名对应的所有值，则调用headers(name)。

如果要获取所有的headers，可以使用Headers这个类来按序号获取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发送字符串

以下示例把一个markdown文件发送到服务器，该服务器会把markdown渲染为HTML。注意此时请求的body是在内存中的，所以尽量避免发送大于1MB的文件。

  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 {    String postBody = ""        + "Releases\n"        + "--------\n"        + "\n"        + " * _1.0_ May 6, 2013\n"        + " * _1.1_ June 15, 2013\n"        + " * _1.2_ August 11, 2013\n";    Request request = new Request.Builder()        .url("https://api.github.com/markdown/raw")        .post(RequestBody.create(MEDIA_TYPE_MARKDOWN, postBody))        .build();    Response response = client.newCall(request).execute();    if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);    System.out.println(response.body().string());  }

流式发送Post请求

以下的示例以写入Okio缓存池的形式发送Post请求，如果想要使用OutputStream可以调用BufferedSink.outputStream()来获取。

  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\n");        sink.writeUtf8("-------\n");        for (int i = 2; i <= 997; i++) {          sink.writeUtf8(String.format(" * %s = %s\n", 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());  }

Post发送文件

  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());  }

Post发送表单

使用FormBody.Builder()来构建一个表单形式的请求体。表单的键值对会使用适配HTML表单的URL编码处理。

  private final OkHttpClient client = new OkHttpClient();  public void run() throws Exception {    RequestBody formBody = new FormBody.Builder()        .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());  }

Post一个multipart请求

MultipartBody.Builder可以构建一个与HTML文件上传表单匹配的复杂的请求体。multipart请求体的本身也是一个请求体，还可以定义自己的headers。如果有相应headers的话，应该是用来描述这个小请求体的，比如说Content-Disposition。如果文件长度或者文件类型可知的话，就会自动加上Content-Length和Content-Type头部。

  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 MultipartBody.Builder()        .setType(MultipartBody.FORM)        .addFormDataPart("title", "Square Logo")        .addFormDataPart("image", "logo-square.png",            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());  }

使用Gson解析JSON格式的response

response.body().charStream()是使用Content-Type这个响应头指定的字符集来解码响应体。如果没有指定的话默认使用UTF-8。

  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<String, GistFile> entry : gist.files.entrySet()) {      System.out.println(entry.getKey());      System.out.println(entry.getValue().content);    }  }  static class Gist {    Map<String, GistFile> files;  }  static class GistFile {    String content;  }

Response的缓存

如果要缓存response的话，要有一个限制大小的可读写的缓存目录。注意这个目录必须是private，其他应用不能访问到。

大部分应用都应该只调用一次new OkHttpClient()，配置好相应缓存实例，保证只有一个缓存实例读写缓存目录避免出错。

Response caching uses HTTP headers for all configuration. You can add request headers like Cache-Control: max-stale=3600 and OkHttp’s cache will honor them. Your webserver configures how long responses are cached with its own response headers, like Cache-Control: max-age=9600. There are cache headers to force a cached response, force a network response, or force the network response to be validated with a conditional GET.

  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.Builder()        .cache(cache)        .build();  }  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());    Response response2 = client.newCall(request).execute();    if (!response2.isSuccessful()) throw new IOException("Unexpected code " + response2);    String response2Body = response2.body().string();    System.out.println("Response 2 response:          " + response2);    System.out.println("Response 2 cache response:    " + response2.cacheResponse());    System.out.println("Response 2 network response:  " + response2.networkResponse());    System.out.println("Response 2 equals Response 1? " + response1Body.equals(response2Body));  }

使用CacheControl.FORCE_NETWORK 和CacheControl.FORCE_CACHE来强制使用网络或者强制使用缓存来获取response。注意当使用强制缓存的时候，如果需要网络请求才能获取到response，就会返回一个504 Unsatisfiable Request的response。

取消请求

调用Call.cancel()来立即取消一个同步或者异步请求，如果正在编写请求或者读取响应的过程中，就会抛出一个IOException。

 private final ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);  private final OkHttpClient client = new OkHttpClient();  public void run() throws Exception {    Request request = new Request.Builder()        .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay.        .build();    final long startNanos = System.nanoTime();    final Call call = client.newCall(request);    // Schedule a job to cancel the call in 1 second.    executor.schedule(new Runnable() {      @Override public void run() {        System.out.printf("%.2f Canceling call.%n", (System.nanoTime() - startNanos) / 1e9f);        call.cancel();        System.out.printf("%.2f Canceled call.%n", (System.nanoTime() - startNanos) / 1e9f);      }    }, 1, TimeUnit.SECONDS);    try {      System.out.printf("%.2f Executing call.%n", (System.nanoTime() - startNanos) / 1e9f);      Response response = call.execute();      System.out.printf("%.2f Call was expected to fail, but completed: %s%n",          (System.nanoTime() - startNanos) / 1e9f, response);    } catch (IOException e) {      System.out.printf("%.2f Call failed as expected: %s%n",          (System.nanoTime() - startNanos) / 1e9f, e);    }  }

设置超时

OkHttp支持连接、读取、写入三种超时。

  private final OkHttpClient client;  public ConfigureTimeouts() throws Exception {    client = new OkHttpClient.Builder()        .connectTimeout(10, TimeUnit.SECONDS)        .writeTimeout(10, TimeUnit.SECONDS)        .readTimeout(30, TimeUnit.SECONDS)        .build();  }  public void run() throws Exception {    Request request = new Request.Builder()        .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay.        .build();    Response response = client.newCall(request).execute();    System.out.println("Response completed: " + response);  }

单次请求设置

所有的Http设置都存在于OkHttpClient当中。如果需要改变设置的时候，可以调用OkHttpClient.newBuilder()来返回一个与原client相同连接池、分配者和配置的builder，然后可以进行修改，比如下面对于两个请求配置了两个不同的读取超时时间：

  private final OkHttpClient client;  public ConfigureTimeouts() throws Exception {    client = new OkHttpClient.Builder()        .connectTimeout(10, TimeUnit.SECONDS)        .writeTimeout(10, TimeUnit.SECONDS)        .readTimeout(30, TimeUnit.SECONDS)        .build();  }  public void run() throws Exception {    Request request = new Request.Builder()        .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay.        .build();    Response response = client.newCall(request).execute();    System.out.println("Response completed: " + response);  }

  private final OkHttpClient client = new OkHttpClient();  public void run() throws Exception {    Request request = new Request.Builder()        .url("http://httpbin.org/delay/1") // This URL is served with a 1 second delay.        .build();    try {      // Copy to customize OkHttp for this request.      OkHttpClient copy = client.newBuilder()          .readTimeout(500, TimeUnit.MILLISECONDS)          .build();      Response response = copy.newCall(request).execute();      System.out.println("Response 1 succeeded: " + response);    } catch (IOException e) {      System.out.println("Response 1 failed: " + e);    }    try {      // Copy to customize OkHttp for this request.      OkHttpClient copy = client.newBuilder()          .readTimeout(3000, TimeUnit.MILLISECONDS)          .build();      Response response = copy.newCall(request).execute();      System.out.println("Response 2 succeeded: " + response);    } catch (IOException e) {      System.out.println("Response 2 failed: " + e);    }  }

处理认证：

对于未认证的请求，OkHttp会自动重试。如果请求返回401 Not Authorized，就需要提供一个Authenticator进行认证，如果不提供就不会重试了。提供Authenticator的话就是创建一个包含Authenticator的新request。

调用Response.challenges()来获取认证要求的schemes和范围。调用Credentials.basic(username, password)来设置用户名密码。

  private final OkHttpClient client;  public Authenticate() {    client = new OkHttpClient.Builder()        .authenticator(new Authenticator() {          @Override public Request authenticate(Route route, Response response) throws IOException {            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();          }        })        .build();  }  public void run() throws Exception {    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());  }

假如已经重试过了可以返回null取消重试：

  if (credential.equals(response.request().header("Authorization"))) {    return null;    }

或者根据重试次数决定是否重试：

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