Okhttp3 如何发送请求？

最近研究 Okhttp3, 把项目 down 下来后，发现不能编译，真实尴尬。平时使用的都是 gradle, 但是该项目使用 maven，导入 idea 后，摸索两下，用界面的命令行搞起。

image.png

项目中有好多 model, 本次主要看看 Okhttp3 的 get/post 请求。其实我们自己很容易就能写出来，不过还是看看 官方 demo 的写法吧。

get 请求

public class GetExample {
  OkHttpClient client = new OkHttpClient();

  String run(String url) throws IOException {
    Request request = new Request.Builder()
        .url(url)
        .build();

    try (Response response = client.newCall(request).execute()) {
      return response.body().string();
    }
  }

  public static void main(String[] args) throws IOException {
    GetExample example = new GetExample();
    String response = example.run("https://raw.github.com/square/okhttp/master/README.md");
    System.out.println(response);
  }
}

这个里面需要提到的是 try(需要一次捕获的代码){正常后处理的代码} 这是 java 7.0 以上的 try catch 结构，操作方便。

post 请求

public class PostExample {
  public static final MediaType JSON
      = MediaType.parse("application/json; charset=utf-8");

  OkHttpClient client = new OkHttpClient();

  String post(String url, String json) throws IOException {
    RequestBody body = RequestBody.create(JSON, json);
    Request request = new Request.Builder()
        .url(url)
        .post(body)
        .build();
    try (Response response = client.newCall(request).execute()) {
      return response.body().string();
    }
  }

  String bowlingJson(String player1, String player2) {
    return "{'winCondition':'HIGH_SCORE',"
        + "'name':'Bowling',"
        + "'round':4,"
        + "'lastSaved':1367702411696,"
        + "'dateStarted':1367702378785,"
        + "'players':["
        + "{'name':'" + player1 + "','history':[10,8,6,7,8],'color':-13388315,'total':39},"
        + "{'name':'" + player2 + "','history':[6,10,5,10,10],'color':-48060,'total':41}"
        + "]}";
  }

  public static void main(String[] args) throws IOException {
    PostExample example = new PostExample();
    String json = example.bowlingJson("Jesse", "Jake");
    String response = example.post("http://www.roundsapp.com/post", json);
    System.out.println(response);
  }
}

重点在这里『RequestBody.create(JSON, json)』， 构建 post 的 body 的时候，直接传入 mediaType 和 json 内容即可构建成功。

下面还有好多，可以直接在 github 上查看：

image.png

异步 get 请求，猜猜结果是什么？

public final class AsynchronousGet {
  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 {
        try (ResponseBody responseBody = response.body()) {
          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(responseBody.string());
        }
      }
    });
    System.out.println(" 异步了么？");
  }

  public static void main(String... args) throws Exception {
    new AsynchronousGet().run();
  }
}

结果亮起来了：

image.png

需要用户登录后才能访问接口

我们 尝试直接访问 http://publicobject.com/secrets/hellosecret.txt , 会强制我们登录，否则就没有返回值。
登录名： jesse
登陆密码： password1

会看到 android 的密钥哈

public final class Authenticate {
  private final OkHttpClient client;

  public Authenticate() {
    client = new OkHttpClient.Builder()
        .authenticator(new Authenticator() {
          @Override public Request authenticate(Route route, Response response) throws IOException {
            if (response.request().header("Authorization") != null) {
              return null; // Give up, we've already attempted to authenticate.
            }

            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();

    try (Response response = client.newCall(request).execute()) {
      if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

      System.out.println(response.body().string());
    }
  }

  public static void main(String... args) throws Exception {
    new Authenticate().run();
  }
}