Android | 14 个例子带你完全入门 OkHttp-六虎

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OkHttp 是 Android 最盛行的网络恳求库，由 square 公司开发。除此之外，square 还开源了众多受欢迎的库，如 okio，picasso，retrofit，moshi 等。总归，square 是一个特别神奇的安排，成员都是职业威望，经验丰富的开发者。

本文演示了14个比方，覆盖了 OkHttp 一切可能运用到的用法，能够让咱们快速入门。这些在日常开发中彻底够用。

运用过程

OkHttp 的运用有一定的过程，大体如下。

初始化 OkHttpClient，官方主张整个应用只运用一个OkHttpClient对象。OkHttpClient能够设置缓存和超时时刻等。
关于一个恳求，实例化一个Request对象，构建恳求的url，恳求体等信息。
运用OkHttpClient发送同步或异步恳求，并获取呼应成果。

能够看见运用 OkHttp 发送网络恳求十分的简略，只需求简略的3个过程。本文OkHttpClient的装备如下所示。设置衔接超时为10s，写入超时为10s，读取超时为 30s，调用超时为 10s。

private final OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .connectTimeout(10, TimeUnit.SECONDS)
    .writeTimeout(10, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .callTimeout(10, TimeUnit.SECONDS)
    .build();

同步 Get 恳求

同步恳求的意思是“履行恳求”和“获取回来成果”是同步的，有先后顺序的。关于同步恳求，OkHttp 内部不会敞开线程去履行。恳求和成果回来都在调用线程中履行。下面代码首先经过Builder形式创建了一个Request，url是https://publicobject.com/helloworld.txt，然后运用okHttpClient发送同步恳求，调用线程会堵塞等待直到成果回来或者产生异常而退出。

public void synchronousGet() throws IOException {
    Request request = new Request.Builder()
            .url("https://publicobject.com/helloworld.txt")
            .build();
    // 运用 execute 发送同步恳求，会堵塞直到成果回来
    try(Response response = okHttpClient.newCall(request).execute()) {
        if(!response.isSuccessful()) {
            throw new IOException("Unexpected code " + response);
        }
        Headers responseHeaders = response.headers();
        // 打印呼应报文的一切头字段
        for (int i=0;i <responseHeaders.size(); i++) {
            System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
        }
        // 假如 呼应体 > 1MB，应避免运用 string() 办法，由于它会将整个文档加载到内存中。这种情况下，应该运用流的办法来处理 body
        System.out.println(response.body().string());
    }
}

上述代码打印出呼应报文的一切头字段。

Server: nginx/1.10.3 (Ubuntu)
Date: Fri, 03 Feb 2023 09:18:44 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

异步 Get 恳求

异步恳求和同步恳求刚好相反。关于异步恳求来说，OkHttp 内部会敞开线程去履行，回来成果会在线程中回调。所以不要在回调函数onFailure或onResponse**中去操作UI。**如有必要，能够配合运用Handler或RxJava切换到主线程操作。

public void asynchronousGet(){
    Request request = new Request.Builder()
            .url("https://publicobject.com/helloworld.txt")
            .build();
    // 运用 enqueue 发送异步恳求，调用线程不会堵塞
    okHttpClient.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 {
            System.out.println("Current thread: " + Thread.currentThread().getName());
            try(ResponseBody responseBody = response.body()) {
                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(responseBody.string());
            }
        }
    });
}

一个头字段设置多个值

OkHttp 支撑运用addHeader办法对一个头字段设置多个值。

public void accessHeaders() throws Exception {
    Request request = new Request.Builder()
            .url("https://api.github.com/repos/square/okhttp/issues")
            .header("User-Agent", "OkHttp Headers.java")
            // OkHttp 支撑一个头字段设置多个值
            .addHeader("Accept", "application/json; q=0.5")
            .addHeader("Accept", "application/vnd.github.v3+json")
            .build();
    try (Response response = okHttpClient.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"));
    }
}

程序打印成果。

Server: GitHub.com
Date: Mon, 06 Feb 2023 07:16:13 GMT
Vary: [Accept, Accept-Encoding, Accept, X-Requested-With]

Post 办法提交 String

OkHttp 中但凡 Post 恳求必须指定恳求体的媒体类型，下面程序运用 Post 办法向服务器提交一个字符串，媒体类型是text/x-markdown; charset=utf-8。

public static final MediaType MEDIA_TYPE_MARKDOWN = MediaType.parse("text/x-markdown; charset=utf-8");
public void postString() 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 办法恳求，并指定恳求体的媒体类型
            .post(RequestBody.create(MEDIA_TYPE_MARKDOWN, postBody))
            .build();
    try (Response response = okHttpClient.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        System.out.println(response.body().string());
    }
}

程序打印成果。

<h2><a id="user-content-releases" class="anchor" aria-hidden="true" href="#releases"><span aria-hidden="true" class="octicon octicon-link"></span></a>Releases</h2>
<ul>
<li>
<em>1.0</em> May 6, 2013</li>
<li>
<em>1.1</em> June 15, 2013</li>
<li>
<em>1.2</em> August 11, 2013</li>
</ul>

Post 办法提交流

OkHttp 答应咱们将恳求体的内容以流的办法写入，只需重写RequestBody的contentType和writeTo办法。下面代码在writeTo办法中向输出流写入了2到997对应的素因子乘积。

public void postStreaming() throws Exception {
    // 重写 contentType 和 writeTo 办法
    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();
    try (Response response = okHttpClient.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        System.out.println(response.body().string());
    }
}

打印出呼应报文的呼应体。

<h2><a id="user-content-numbers" class="anchor" aria-hidden="true" href="#numbers"><span aria-hidden="true" class="octicon octicon-link"></span></a>Numbers</h2>
<ul>
<li>2 = 2</li>
<li>3 = 3</li>
<li>4 = 2  2</li>
<li>5 = 5</li>
<li>6 = 3  2</li>
<li>7 = 7</li>
<li>8 = 2  2  2</li>
...
<li>992 = 31  2  2  2  2  2</li>
<li>993 = 331  3</li>
<li>994 = 71  7  2</li>
<li>995 = 199  5</li>
<li>996 = 83  3  2  2</li>
<li>997 = 997</li>
</ul>

Post 办法提交文件

OkHttp 提交文件很简略。和提交字符串一样，只需将文件作为恳求体。

public void postFile() throws Exception {
    File file = new File("test.txt");
    Request request = new Request.Builder()
            .url("https://api.github.com/markdown/raw")
            // 直接传入 file 即可
            .post(RequestBody.create(MEDIA_TYPE_MARKDOWN, file))
            .build();
    try (Response response = okHttpClient.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        System.out.println(response.body().string());
    }
}

程序打印成果。

<p>this is a test.</p>

Post 办法提交表单

FormBody是RequestBody的子类，运用FormBody能够轻松的将恳求参数以表单编码办法提交。FormBody默认的媒体类型是application/x-www-form-urlencoded。

public void postForm() throws Exception {
    RequestBody formBody = new FormBody.Builder()
            .add("search", "Jurassic Park")
            .build();
    Request request = new Request.Builder()
            // 该 url 被墙，暂时无法访问
            // java.net.SocketTimeoutException: connect timed out
            .url("https://en.wikipedia.org/w/index.php")
            .post(formBody)
            .build();
    try (Response response = okHttpClient.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        System.out.println(response.body().string());
    }
}

Post 办法提交分块恳求

当你要在一个恳求中同时提交多种类型的数据时，能够运用MultipartBody来完成这个任务。下面程序提交了字符串和图片两种不同的数据。

public void postMultipartBody() 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("logo-square.png")))
            .build();
    Request request = new Request.Builder()
            .header("Authorization", "Client-ID " + IMGUR_CLIENT_ID)
            // 该 url 被墙，暂时无法访问
            // java.net.SocketTimeoutException: connect timed out
            .url("https://api.imgur.com/3/image")
            .post(requestBody)
            .build();
    try (Response response = okHttpClient.newCall(request).execute()) {
            if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
            System.out.println(response.body().string());
    }
}

运用 Moshi 解析 Json 呼应

Moshi 是一个序列/反序列化库。下面代码简略演示了它的用法，当然你还能够运用 Gson 等其他盛行的框架。

// Moshi
private final Moshi moshi = new Moshi.Builder().build();
private final JsonAdapter<Gist> gistJsonAdapter = moshi.adapter(Gist.class);
public void moshiParse() throws Exception {
    Request request = new Request.Builder()
            .url("https://api.github.com/gists/c2a7c39532239ff261be")
            .build();
    try (Response response = okHttpClient.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        // 运用 moshi 反序列化回来成果
        Gist gist = gistJsonAdapter.fromJson(response.body().source());
        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;
}

缓存呼应

OkHttp 能够以文件的办法缓存来自服务器的呼应，节约网络流量。修正OkHttpClient的装备，添加缓存功用。设置缓存巨细为 10M，缓存文件目录为okhttpcache。

// Cache, 装备 OkHttp 本地缓存
int cacheSize = 10 * 1024 * 1024; // 10 MiB
Cache cache = new Cache(new File("okhttpcache"), cacheSize);
// client
private final OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .cache(cache)
    .connectTimeout(10, TimeUnit.SECONDS)
    .writeTimeout(10, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .callTimeout(10, TimeUnit.SECONDS)
    .build();

下面程序恳求了同一个url两次。调用cacheResponse两次来调查打印成果，咱们能够得出如下结论。

由于本地没有缓存，第一次调用的第一个恳求会恳求网络，并将呼应缓存到本地。
第一次调用的第二个恳求直接从本地缓存拿到呼应成果，不会走网络恳求。
第2次调用的一切恳求均会从本地缓存拿到呼应成果。

public void cacheResponse() throws Exception {
    Request request = new Request.Builder()
            .url("http://publicobject.com/helloworld.txt")
            .build();
    // 第一次恳求
    String response1Body;
    try (Response response1 = okHttpClient.newCall(request).execute()) {
        if (!response1.isSuccessful()) throw new IOException("Unexpected code " + response1);
        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());
    }
    // 第2次恳求
    String response2Body;
    try (Response response2 = okHttpClient.newCall(request).execute()) {
        if (!response2.isSuccessful()) throw new IOException("Unexpected code " + response2);
        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));
}

程序打印成果。

// 第一次调用打印
Response 1 response:          Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 1 cache response:    null
Response 1 network response:  Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 2 response:          Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 2 cache response:    Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 2 network response:  null
Response 2 equals Response 1? true
// 第2次调用打印
Response 1 response:          Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 1 cache response:    Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 1 network response:  null
Response 2 response:          Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 2 cache response:    Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Response 2 network response:  null
Response 2 equals Response 1? true

撤销正在履行的恳求

运用 call.cancel() 能够当即停止正在进行的恳求，同步和异步恳求都能够撤销。这种功用能够节约网络，例如当用户开应用程序时。下面恳求的url会有2s的推迟，在一个线程中咱们会在1s后撤销这个恳求，随后程序抛出了异常。

public void cancelCall() 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 = okHttpClient.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);
    System.out.printf("%.2f Executing call.%n", (System.nanoTime() - startNanos) / 1e9f);
    try (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);
    }
}

程序打印成果。

0.00 Executing call.
1.02 Canceling call.
1.02 Canceled call.
1.02 Call failed as expected: java.io.IOException: Canceled

设置超时

OkHttp 支撑设置衔接、写入、读取和彻底调用超时。下面程序恳求的url有10s的推迟。而咱们OkHttpClient设置的调用超时为10s，所以下面代码将会抛出异常。

public void timeout() throws Exception {
    Request request = new Request.Builder()
            .url("http://httpbin.org/delay/10") // This URL is served with a 10 second delay.
            .build();
    try (Response response = okHttpClient.newCall(request).execute()) {
        System.out.println("Response completed: " + response);
    }
}

程序打印成果。

java.io.InterruptedIOException: timeout
at okhttp3.internal.connection.RealCall.timeoutExit(RealCall.kt:398)
at okhttp3.internal.connection.RealCall.callDone(RealCall.kt:360)

改动单个 Call 的装备

OkHttpClient的装备对一切的恳求都生效，有时候咱们想对某个恳求单独装备，比方改动超时时刻等。这个时候就能够运用newBuilder办法，newBuilder会复制全局OkHttpClient成员变量的值重新生成一个OkHttpClient实例回来。

public void perCallConfiguration() throws Exception {
    Request request = new Request.Builder()
            .url("http://httpbin.org/delay/1") // This URL is served with a 1 second delay.
            .build();
    // Copy to customize OkHttp for this request.
    OkHttpClient client1 = okHttpClient.newBuilder()
            .readTimeout(500, TimeUnit.MILLISECONDS)
            .build();
    try (Response response = client1.newCall(request).execute()) {
        System.out.println("Response 1 succeeded: " + response);
    } catch (IOException e) {
        System.out.println("Response 1 failed: " + e);
    }
    // Copy to customize OkHttp for this request.
    OkHttpClient client2 = okHttpClient.newBuilder()
            .readTimeout(3000, TimeUnit.MILLISECONDS)
            .build();
    try (Response response = client2.newCall(request).execute()) {
        System.out.println("Response 2 succeeded: " + response);
    } catch (IOException e) {
        System.out.println("Response 2 failed: " + e);
    }
}

程序打印成果。

Response 1 failed: java.net.SocketTimeoutException: Read timed out
Response 2 succeeded: Response{protocol=http/1.1, code=200, message=OK, url=http://httpbin.org/delay/1}

身份验证

在恳求需求身份验证的资源时，若没有权限服务器通常会回来401来告知客户端身份验证的计划和受保护的资源范。OkHttp 能够主动重试未经身份验证的恳求，当呼应为401未授权时，咱们构建一个包括凭证的新恳求。下面程序恳求的url需求身份验证，在authenticator办法中第一次回来了401，所以咱们添加了头字段Authorization，并依照服务器要求的身份验证计划生成了凭证再次发送恳求。

public void authenticate() throws Exception {
    OkHttpClient okHttpClient1 = okHttpClient.newBuilder()
        .authenticator(new Authenticator() {
            @Nullable
            @Override
            public Request authenticate(@Nullable 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();
    Request request = new Request.Builder()
            .url("http://publicobject.com/secrets/hellosecret.txt")
            .build();
    try (Response response = okHttpClient1.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        System.out.println(response.body().string());
    }
}

程序打印成果。

Authenticating for response: Response{protocol=http/1.1, code=401, message=Unauthorized, url=https://publicobject.com/secrets/hellosecret.txt}
Challenges: [Basic authParams={realm=OkHttp Secrets}]

写在最终

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Android | 14 个例子带你完全入门 OkHttp

运用过程

同步 Get 恳求

异步 Get 恳求

一个头字段设置多个值

Post 办法提交 String

Post 办法提交流

Post 办法提交文件

Post 办法提交表单

Post 办法提交分块恳求

运用 Moshi 解析 Json 呼应

缓存呼应

撤销正在履行的恳求

设置超时

改动单个 Call 的装备

身份验证

写在最终

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