【Android -- 网络请求】网络请求（Okhttp）

前言

目前大量流行库都以 ​​OkHttp​​​ 作为底层网络请求框架或提供支持，比如：Retrofit、Glide、Fresco、Moshi、Picasso 等。
常用的状态码：

• 100~199：指示信息，表示请求已接收，继续处理
• 200~299：请求成功，表示请求已被成功接收、理解
• 300~399：重定向，要完成请求必须进行更进一步的操作
• 400~499：客户端错误，请求有语法错误或请求无法实现
• 500~599：服务器端错误，服务器未能实现合法的请求

特点

• 同时支持 Http1.1 和 Http2.0
• 同时支持同步与异步请求；
• 同时具备 Http 与 WebSocket 功能；
• 拥有自动维护的 socket 连接池，减少握手次数；
• 拥有队列线程池，轻松写并发；
• 拥有 Interceptors(拦截器)，轻松处理请求与响应额外需求。

使用

在 AndroidManifest.xml 中添加网络访问权限：

<uses-permission android:name="android.permission.INTERNET"/>

在 app/build.gradle 的 dependencies 中添加如下依赖：

implementation("com.squareup.okhttp3:okhttp:4.9.3")
implementation("com.squareup.okhttp3:logging-interceptor:4.9.3")

GET 请求

同步 GET 请求

同步 GET 请求是指一直等待 http 请求，直到返回了响应。在这之间会阻塞线程，所以同步请求不能在 Android 的主线程中执行，否则会报 NetworkMainThreadException.

String BASE_URL = "http://wwww.baidu.com";
//1.新建OKHttpClient客户端
OkHttpClient okHttpClient = new OkHttpClient();
//2. 新建一个Request对象
final Request request = new Request.Builder()
.url(BASE_URL)
.build();

final Call call = okHttpClient.newCall(request);
new Thread(new Runnable() {
@Override
public void run() {
try {
//3.Response为 OKHttp 中的响应
Response response = call.execute();
Log.d(TAG, "run: " + response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();

异步 GET 请求

异步 GET 请求是指在另外的工作线程中执行 http 请求，请求时不会阻塞当前的线程，所以可以在 Android 主线程中使用。

String BASE_URL = "http://wwww.baidu.com";
//1.新建OKHttpClient客户端
OkHttpClient okHttpClient = new OkHttpClient();
//2. 新建一个Request对象
final Request request = new Request.Builder()
.url(BASE_URL)
.build();

final Call call = okHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {
Log.d(TAG, "onResponse: " + response.body().string());
}

@Override
public void onFailure(@NotNull Call call, @NotNull IOException e) {
Log.d(TAG, "onFailure: ");
}
});

说明：无论是同步还是异步请求，接收到的 response 结果都是在子线程中，onResponse、onFailure 的回调是在子线程中的，我们需要切换到主线程才能操作 UI 控件。

POST 请求

POST 方式提交 String

MediaType mediaType = MediaType.parse("text/x-markdown; charset=utf-8");
String requestBody = "I am Kevin.";
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 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());
}

@Override
public void onFailure(Call call, IOException e) {
Log.d(TAG, "onFailure: " + e.getMessage());
}
});

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 Kevin.");
}
};

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());
}
});

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());
}
});

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());
}
});

拦截器-interceptor

简单实例

需求：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。

自定义 LoggingInterceptor.java

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;
}
}

使用

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();
}
}
});

打印日志

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