Okhttp3基本使用

I.簡(jiǎn)介

HTTP是現(xiàn)代應(yīng)用常用的一種交換數(shù)據(jù)和媒體的網(wǎng)絡(luò)方式,高效地使用HTTP能讓資源加載更快,節(jié)省帶寬。OkHttp是一個(gè)高效的HTTP客戶端,它有以下默認(rèn)特性:

  • 支持HTTP/2,允許所有同一個(gè)主機(jī)地址的請(qǐng)求共享同一個(gè)socket連接
  • 連接池減少請(qǐng)求延時(shí)
  • 透明的GZIP壓縮減少響應(yīng)數(shù)據(jù)的大小
  • 緩存響應(yīng)內(nèi)容,避免一些完全重復(fù)的請(qǐng)求

當(dāng)網(wǎng)絡(luò)出現(xiàn)問(wèn)題的時(shí)候OkHttp依然堅(jiān)守自己的職責(zé),它會(huì)自動(dòng)恢復(fù)一般的連接問(wèn)題,如果你的服務(wù)有多個(gè)IP地址,當(dāng)?shù)谝粋€(gè)IP請(qǐng)求失敗時(shí),OkHttp會(huì)交替嘗試你配置的其他IP,OkHttp使用現(xiàn)代TLS技術(shù)(SNI, ALPN)初始化新的連接,當(dāng)握手失敗時(shí)會(huì)回退到TLS 1.0。

note: OkHttp 支持 Android 2.3 及以上版本Android平臺(tái), 對(duì)于 Java, JDK 1.7及以上.

對(duì)于Okhttp3的源碼閱讀預(yù)計(jì)會(huì)寫(xiě)3篇文章來(lái)總結(jié):

II.使用

OkHttp的使用是非常簡(jiǎn)單的. 它的請(qǐng)求/響應(yīng) API 使用構(gòu)造器模式builders來(lái)設(shè)計(jì),它支持阻塞式的同步請(qǐng)求和帶回調(diào)的異步請(qǐng)求。

Download OkHttp3

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

當(dāng)你看到這的時(shí)候,可能最新的穩(wěn)定版已經(jīng)不是3.10.0了,你需要移步官方GitHub來(lái)查看最新版本。 官方地址 https://github.com/square/okhttp,另外不要忘了在清單文件聲明訪問(wèn)Internet的權(quán)限,如果使用 DiskLruCache,那還得聲明寫(xiě)外存的權(quán)限。

1.1. 異步GET請(qǐng)求

-new OkHttpClient;
-構(gòu)造Request對(duì)象;
-通過(guò)前兩步中的對(duì)象構(gòu)建Call對(duì)象;
-通過(guò)Call#enqueue(Callback)方法來(lái)提交異步請(qǐng)求;

String url = "http://wwww.baidu.com";
OkHttpClient okHttpClient = new OkHttpClient();
final Request request = new Request.Builder()
        .url(url)
        .get()//默認(rèn)就是GET請(qǐng)求,可以不寫(xiě)
        .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());
    }
});

異步發(fā)起的請(qǐng)求會(huì)被加入到 Dispatcher 中的 runningAsyncCalls雙端隊(duì)列中通過(guò)線程池來(lái)執(zhí)行。

1.2. 同步GET請(qǐng)求

前面幾個(gè)步驟和異步方式一樣,只是最后一部是通過(guò) Call#execute() 來(lái)提交請(qǐng)求,注意這種方式會(huì)阻塞調(diào)用線程,所以在Android中應(yīng)放在子線程中執(zhí)行,否則有可能引起ANR異常,Android3.0 以后已經(jīng)不允許在主線程訪問(wèn)網(wǎng)絡(luò)。

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

這種方式與前面的區(qū)別就是在構(gòu)造Request對(duì)象時(shí),需要多構(gòu)造一個(gè)RequestBody對(duì)象,用它來(lái)攜帶我們要提交的數(shù)據(jù)。在構(gòu)造 RequestBody 需要指定MediaType,用于描述請(qǐng)求/響應(yīng) body 的內(nèi)容類型,關(guān)于 MediaType 的更多信息可以查看 RFC 2045,RequstBody的幾種構(gòu)造方式:

image
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());
    }
});

響應(yīng)內(nèi)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方式提交表單

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());
    }
});

提交表單時(shí),使用 RequestBody 的實(shí)現(xiàn)類FormBody來(lái)描述請(qǐng)求體,它可以攜帶一些經(jīng)過(guò)編碼的 key-value 請(qǐng)求體,鍵值對(duì)存儲(chǔ)在下面兩個(gè)集合中:

  private final List<String> encodedNames;
  private final List<String> encodedValues;

2.5. POST方式提交分塊請(qǐng)求

MultipartBody 可以構(gòu)建復(fù)雜的請(qǐng)求體,與HTML文件上傳形式兼容。多塊請(qǐng)求體中每塊請(qǐng)求都是一個(gè)請(qǐng)求體,可以定義自己的請(qǐng)求頭。這些請(qǐng)求頭可以用來(lái)描述這塊請(qǐng)求,例如它的 Content-Disposition 。如果 Content-LengthContent-Type 可用的話,他們會(huì)被自動(dòng)添加到請(qǐng)求頭中。

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());

        }

    });
}

III.攔截器-interceptor

OkHttp的攔截器鏈可謂是其整個(gè)框架的精髓,用戶可傳入的 interceptor 分為兩類:
①一類是全局的 interceptor,該類 interceptor 在整個(gè)攔截器鏈中最早被調(diào)用,通過(guò) OkHttpClient.Builder#addInterceptor(Interceptor) 傳入;
②另外一類是非網(wǎng)頁(yè)請(qǐng)求的 interceptor ,這類攔截器只會(huì)在非網(wǎng)頁(yè)請(qǐng)求中被調(diào)用,并且是在組裝完請(qǐng)求之后,真正發(fā)起網(wǎng)絡(luò)請(qǐng)求前被調(diào)用,所有的 interceptor 被保存在 List<Interceptor> interceptors 集合中,按照添加順序來(lái)逐個(gè)調(diào)用,具體可參考 RealCall#getResponseWithInterceptorChain() 方法。通過(guò) OkHttpClient.Builder#addNetworkInterceptor(Interceptor) 傳入;

這里舉一個(gè)簡(jiǎn)單的例子,例如有這樣一個(gè)需求,我要監(jiān)控App通過(guò) OkHttp 發(fā)出的所有原始請(qǐng)求,以及整個(gè)請(qǐng)求所耗費(fèi)的時(shí)間,針對(duì)這樣的需求就可以使用第一類全局的 interceptor 在攔截器鏈頭去做。

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;
    }
}

針對(duì)這個(gè)請(qǐng)求,打印出來(lái)的結(jié)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

注意到一點(diǎn)是這個(gè)請(qǐng)求做了重定向,原始的 request urlhttp://www.publicobject.com/helloworld.tx,而響應(yīng)的 request urlhttps://publicobject.com/helloworld.txt,這說(shuō)明一定發(fā)生了重定向,但是做了幾次重定向其實(shí)我們這里是不知道的,要知道這些的話,可以使用 addNetworkInterceptor()去做。更多的關(guān)于 interceptor的使用以及它們各自的優(yōu)缺點(diǎn),請(qǐng)移步OkHttp官方說(shuō)明文檔

image

IV. 自定義dns服務(wù)

Okhttp默認(rèn)情況下使用的是系統(tǒng)

V.其他

  1. 推薦讓 OkHttpClient 保持單例,用同一個(gè) OkHttpClient 實(shí)例來(lái)執(zhí)行你的所有請(qǐng)求,因?yàn)槊恳粋€(gè) OkHttpClient 實(shí)例都擁有自己的連接池和線程池,重用這些資源可以減少延時(shí)和節(jié)省資源,如果為每個(gè)請(qǐng)求創(chuàng)建一個(gè) OkHttpClient 實(shí)例,顯然就是一種資源的浪費(fèi)。當(dāng)然,也可以使用如下的方式來(lái)創(chuàng)建一個(gè)新的 OkHttpClient 實(shí)例,它們共享連接池、線程池和配置信息。
    OkHttpClient eagerClient = client.newBuilder()
        .readTimeout(500, TimeUnit.MILLISECONDS)
        .build();
    Response response = eagerClient.newCall(request).execute();

  1. 每一個(gè)Call(其實(shí)現(xiàn)是RealCall)只能執(zhí)行一次,否則會(huì)報(bào)異常,具體參見(jiàn) RealCall#execute()

</article>

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