OkHttp的使用

Download OkHttp3

implementation 'com.squareup.okhttp3:okhttp:3.10.0'

1.1. 异步GET请求

-new OkHttpClient;

-构造Request对象；

-通过前两步中的对象构建Call对象；

-通过Call#enqueue(Callback)方法来提交异步请求；

String url = "http://wwww.baidu.com";

OkHttpClient okHttpClient = new OkHttpClient();

final Request request = new Request.Builder()

        .url(url)

        .get()//默认就是GET请求，可以不写

        .build();

Call call = okHttpClient.newCall(request);

call.enqueue(new Callback() {

    @Override

    public void onFailure(Call call, IOException e) {

        Log.d(TAG, "onFailure: ");

    }

    @Override

    public void onResponse(Call call, Response response) throws IOException {

        Log.d(TAG, "onResponse: " + response.body().string());

    }

});

异步发起的请求会被加入到 Dispatcher 中的 runningAsyncCalls双端队列中通过线程池来执行。

1.2. 同步GET请求

前面几个步骤和异步方式一样，只是最后一部是通过 Call#execute() 来提交请求，注意这种方式会阻塞调用线程，所以在Android中应放在子线程中执行，否则有可能引起ANR异常，Android3.0 以后已经不允许在主线程访问网络。

String url = "http://wwww.baidu.com";

OkHttpClient okHttpClient = new OkHttpClient();

final Request request = new Request.Builder()

        .url(url)

        .build();

final Call call = okHttpClient.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();

2.1. POST方式提交String

这种方式与前面的区别就是在构造Request对象时，需要多构造一个RequestBody对象，用它来携带我们要提交的数据。在构造 RequestBody 需要指定MediaType，用于描述请求/响应 body 的内容类型，关于 MediaType 的更多信息可以查看 RFC 2045

request_body

MediaType mediaType = MediaType.parse("text/x-markdown; charset=utf-8");

String requestBody = "I am Jdqm.";

Request request = new Request.Builder()

        .url("https://api.github.com/markdown/raw")

        .post(RequestBody.create(mediaType, requestBody))

        .build();

OkHttpClient okHttpClient = new OkHttpClient();

okHttpClient.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());

    }

});

响应内容

http/1.1 200 OK

Date:Sat, 10 Mar 2018 05:23:20 GMT

Content-Type:text/html;charset=utf-8

Content-Length:18

Server:GitHub.com

Status:200 OK

X-RateLimit-Limit:60

X-RateLimit-Remaining:52

X-RateLimit-Reset:1520661052

X-CommonMarker-Version:0.17.4

Access-Control-Expose-Headers:ETag, Link, Retry-After, X-GitHub-OTP, X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset, X-OAuth-Scopes, X-Accepted-OAuth-Scopes, X-Poll-Interval

Access-Control-Allow-Origin:*

Content-Security-Policy:default-src 'none'

Strict-Transport-Security:max-age=31536000; includeSubdomains; preload

X-Content-Type-Options:nosniff

X-Frame-Options:deny

X-XSS-Protection:1; mode=block

X-Runtime-rack:0.019668

Vary:Accept-Encoding

X-GitHub-Request-Id:1474:20A83:5CC0B6:7A7C1B:5AA36BC8

onResponse: <p>I am Jdqm.</p>

2.2 POST方式提交流

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 okHttpClient = new OkHttpClient();

okHttpClient.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());

    }

});

2.3. POST提交文件

MediaType mediaType = MediaType.parse("text/x-markdown; charset=utf-8");

OkHttpClient okHttpClient = new OkHttpClient();

File file = new File("test.md");

Request request = new Request.Builder()

        .url("https://api.github.com/markdown/raw")

        .post(RequestBody.create(mediaType, file))

        .build();

okHttpClient.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());

    }

});

2.4. POST方式提交表单

OkHttpClient okHttpClient = 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();

okHttpClient.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());

    }

});

提交表单时，使用 RequestBody 的实现类FormBody来描述请求体，它可以携带一些经过编码的 key-value 请求体，键值对存储在下面两个集合中：

  private final List<String> encodedNames;

  private final List<String> encodedValues;

2.5. POST方式提交分块请求

MultipartBody 可以构建复杂的请求体，与HTML文件上传形式兼容。多块请求体中每块请求都是一个请求体，可以定义自己的请求头。这些请求头可以用来描述这块请求，例如它的 Content-Disposition 。如果 Content-Length 和 Content-Type 可用的话，他们会被自动添加到请求头中。

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) {

        }

        @Override

        public void onResponse(Call call, Response response) throws IOException {

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

        }

    });

}

3.拦截器-interceptor

OkHttp的拦截器链可谓是其整个框架的精髓，用户可传入的 interceptor 分为两类：

①一类是全局的 interceptor，该类 interceptor 在整个拦截器链中最早被调用，通过 OkHttpClient.Builder#addInterceptor(Interceptor) 传入；

②另外一类是非网页请求的 interceptor ，这类拦截器只会在非网页请求中被调用，并且是在组装完请求之后，真正发起网络请求前被调用，所有的 interceptor 被保存在 List<Interceptor> interceptors 集合中，按照添加顺序来逐个调用，具体可参考 RealCall#getResponseWithInterceptorChain() 方法。通过 OkHttpClient.Builder#addNetworkInterceptor(Interceptor) 传入；

这里举一个简单的例子，例如有这样一个需求，我要监控App通过 OkHttp 发出的所有原始请求，以及整个请求所耗费的时间，针对这样的需求就可以使用第一类全局的 interceptor 在拦截器链头去做。

OkHttpClient okHttpClient = new OkHttpClient.Builder()

        .addInterceptor(new LoggingInterceptor())

        .build();

Request request = new Request.Builder()

        .url("http://www.publicobject.com/helloworld.txt")

        .header("User-Agent", "OkHttp Example")

        .build();

okHttpClient.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 {

        ResponseBody body = response.body();

        if (body != null) {

            Log.d(TAG, "onResponse: " + response.body().string());

            body.close();

        }

    }

});

public class LoggingInterceptor implements Interceptor {

    private static final String TAG = "LoggingInterceptor";

    @Override

    public Response intercept(Chain chain) throws IOException {

        Request request = chain.request();

        long startTime = System.nanoTime();

        Log.d(TAG, String.format("Sending request %s on %s%n%s",

                request.url(), chain.connection(), request.headers()));

        Response response =  chain.proceed(request);

        long endTime = System.nanoTime();

        Log.d(TAG, String.format("Received response for %s in %.1fms%n%s",

                response.request().url(), (endTime - startTime) / 1e6d, response.headers()));

        return response;

    }

}

针对这个请求，打印出来的结果

Sending request http://www.publicobject.com/helloworld.txt on null

User-Agent: OkHttp Example

Received response for https://publicobject.com/helloworld.txt in 1265.9ms

Server: nginx/1.10.0 (Ubuntu)

Date: Wed, 28 Mar 2018 08:19:48 GMT

Content-Type: text/plain

Content-Length: 1759

Last-Modified: Tue, 27 May 2014 02:35:47 GMT

Connection: keep-alive

ETag: "5383fa03-6df"

Accept-Ranges: bytes

注意到一点是这个请求做了重定向，原始的 request url 是 http://www.publicobject.com/helloworld.tx，而响应的 request url 是 https://publicobject.com/helloworld.txt，这说明一定发生了重定向，但是做了几次重定向其实我们这里是不知道的，要知道这些的话，可以使用 addNetworkInterceptor()去做。更多的关于 interceptor的使用以及它们各自的优缺点，请移步OkHttp官方说明文档。

4.其他

推荐让 OkHttpClient 保持单例，用同一个 OkHttpClient 实例来执行你的所有请求，因为每一个 OkHttpClient 实例都拥有自己的连接池和线程池，重用这些资源可以减少延时和节省资源，如果为每个请求创建一个 OkHttpClient 实例，显然就是一种资源的浪费。当然，也可以使用如下的方式来创建一个新的 OkHttpClient 实例，它们共享连接池、线程池和配置信息。

    OkHttpClient eagerClient = client.newBuilder()

        .readTimeout(500, TimeUnit.MILLISECONDS)

        .build();

    Response response = eagerClient.newCall(request).execute();

每一个Call（其实现是RealCall）只能执行一次，否则会报异常，具体参见 RealCall#execute()