To create an OkHttpClient object, you need to import the OkHttp library. You can download the latest version of the jar from:

https://mvnreposiotry.com/artifact/com.squareup.okhttp3/okhttp

Once the OkHttp library is added to your project, you can create a OkHttpClient instance with:

OkHttpClient client = new OkHttpClient();

Note that OkHttp 3.x requires the okhttp, okio, and logging-interceptor jars. You can download the latest versions from the link above. Alternatively, you can use dependency management tools like Gradle or Maven.

Asynchronous GET Request

• Create an OkHttpClient instance.
• Build a Request object.
• Create a Call object using the client and request.
• Submit the request asynchronously using Call#enqueue(Callback).

String url = "http://www.baidu.com";
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        .url(url)
        .get()  // GET is the default method, can be omitted
        .build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

Synchronous GET Request

String url = "http://www.baidu.com";
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        .url(url)
        .build();
Call call = client.newCall(request);
new Thread(new Runnable() {
    @Override
    public void run() {
        try {
            Response response = call.execute();
            Log.d(TAG, "run: " + response.body().string());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}).start();

POST Request with String Body

MediaType mediaType = MediaType.parse("text/plain; charset=utf-8");
String postBody = "I am Jdqm.";
RequestBody requestBody = RequestBody.create(mediaType, postBody);

Request request = new Request.Builder()
        .url("https://api.github.com/markdown/raw")
        .post(requestBody)
        .build();

OkHttpClient client = new OkHttpClient();
client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " + response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ": " + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST Request with Stream Body

RequestBody requestBody = new RequestBody() {
    @Nullable
    @Override
    public MediaType contentType() {
        return MediaType.parse("text/x-markdown; charset=utf-8");
    }

    @Override
    public void writeTo(BufferedSink sink) throws IOException {
        sink.writeUtf8("I am Jdqm.");
    }
};

Request request = new Request.Builder()
        .url("https://api.github.com/markdown/raw")
        .post(requestBody)
        .build();

OkHttpClient client = new OkHttpClient();
client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " + response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ": " + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST Request with File Body

MediaType mediaType = MediaType.parse("text/x-markdown; charset=utf-8");
File file = new File("test.md");
RequestBody requestBody = RequestBody.create(mediaType, file);

Request request = new Request.Builder()
        .url("https://api.github.com/markdown/raw")
        .post(requestBody)
        .build();

OkHttpClient client = new OkHttpClient();
client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " + response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ": " + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST Request with Form Body

OkHttpClient client = new OkHttpClient();
RequestBody requestBody = new FormBody.Builder()
        .add("search", "Jurassic Park")
        .build();

Request request = new Request.Builder()
        .url("https://en.wikipedia.org/w/index.php")
        .post(requestBody)
        .build();

client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " + response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ": " + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST Request witth Multipart Body

private static final String IMGUR_CLIENT_ID = "...";
private static final MediaType MEDIA_TYPE_PNG = MediaType.parse("image/png");

private void postMultipartBody() {
    OkHttpClient client = new OkHttpClient();

    // Use the imgur image upload API as documented at https://api.imgur.com/endpoints/image
    MultipartBody body = new MultipartBody.Builder("AaB03x")
            .setType(MultipartBody.FORM)
            .addPart(
                    Headers.of("Content-Disposition", "form-data; name=\"title\""),
                    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(body)
            .build();

    Call call = client.newCall(request);
    call.enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
            System.out.println("Failure: " + e.getMessage());
        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {
            System.out.println(response.body().string());
        }
    });
}