okhttp3

    最近使用了okhttp3 + mvvm的架构框架，也了解了volley，httpclient，async-http等框架，这些框架之前有的使用过，比起okhttp3来说，okhttp3
有各种自定义拦截器，这里介绍下okhttp的各种方法吧。
                   request = new Request.Builder()
                    .url(API.baseurl + url + "?" + stringJson)
                    .header("ACCESS_TOKEN", Utils.getToken(activity))
                    .build();这是get请求，构造request时候，直接吧参数拼成name=xx&pwd=xx这种表单格式放在?后面。
       RequestBody body;
        if (stringJson == null) {
            body = RequestBody.create("", JSON);
        } else {
            body = RequestBody.create(stringJson, JSON);
        }
        request = new Request.Builder()
                .url(API.baseurl + url)
                .post(body)
                .header("ACCESS_TOKEN", Utils.getToken(activity))
                .build();这是post请求，requestbody.create(stringjson,JSON)，stringjson是json格式的请求参数，后面的JSON是   
    public static final MediaType JSON = MediaType.get("application/json; charset=utf-8");
Content-Type（MediaType），即是Internet Media Type，互联网媒体类型；也叫做MIME类型，在Http协议消息头中，使用Content-Type来表示
具体请求中的媒体类型信息。
用于定义网络文件的类型和网页的编码，决定文件接收方将以什么形式、什么编码读取这个文件。常见的媒体格式类型有：
text/html：HTML格式
text/pain：纯文本格式
image/jpeg：jpg图片格式
application/json：JSON数据格式
application/octet-stream：二进制流数据（如常见的文件下载）
application/x-www-form-urlencoded：form表单encType属性的默认格式，表单数据将以key/value的形式发送到服务端
multipart/form-data：表单上传文件的格式
    返回使用enqueue client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
        }
        @Override
        public void onResponse(Call call, Response response) throws IOException {
        }
    });
    异步返回用这个方法，execute同步阻塞调用用很少吧。
    初始化okhttpclient并设置默认信任所有证书，添加拦截器，为了不断更新token加在请求头给服务端，所以我的初始化代码是这样写的：
private OkHttpClient okhttpclient(Activity activity) {
    try {
        if (client == null) {
            client = new OkHttpClient.Builder().
                    sslSocketFactory(createSSLSocketFactory(), new TrustAllCerts())
                    .hostnameVerifier(new TrustAllHostnameVerifier()).addInterceptor(interceptor(activity))
                    .build();
        }
        return client;
    } catch (Exception e) {
        Utils.log("", "", "okhttp https连接问题");
        return null;
    }
}
    拦截器就是为了拿到服务端response里面的token和打印各种请求和返回，代码如下：
      public class HttpLogInterceptor implements Interceptor {
//    private static final String TAG = HttpLogInterceptor.class.getSimpleName();
private final Charset UTF8 = Charset.forName("UTF-8");
private Activity activity;
public HttpLogInterceptor(Activity activity) {
    this.activity = activity;
}

@Override
public Response intercept(Chain chain) throws IOException {
    Request request = chain.request();
    RequestBody requestBody = request.body();
    String body = null;
    if (requestBody != null) {
        Buffer buffer = new Buffer();
        requestBody.writeTo(buffer);
        Charset charset = UTF8;
        MediaType contentType = requestBody.contentType();
        if (contentType != null) {
            charset = contentType.charset(UTF8);
        }
        body = buffer.readString(charset);
    }

    Log.d("xuedi", "发送请求: method：" + request.method()
            + "\nurl：" + request.url()
            + "\n请求头：" + request.headers()
            + "\n请求参数: " + body);
    long startNs = System.nanoTime();
    Response response = chain.proceed(request);
    long tookMs = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNs);
    if (response.header("ACCESS_TOKEN")!=null) {
        UserLogin.getInstance().setToken(response.header("ACCESS_TOKEN"));
        SharePref.put(activity, API.token, response.header("ACCESS_TOKEN"));
    }
    ResponseBody responseBody = response.body();
    String rBody;
    BufferedSource source = responseBody.source();
    source.request(Long.MAX_VALUE);
    Buffer buffer = source.buffer();

    Charset charset = UTF8;
    MediaType contentType = responseBody.contentType();
    if (contentType != null) {
        try {
            charset = contentType.charset(UTF8);
        } catch (UnsupportedCharsetException e) {
            e.printStackTrace();
        }
    }
    rBody = buffer.clone().readString(charset);

    Log.d("xuedi", "收到: method：" + request.method()+
            "\n响应header："+response.header("ACCESS_TOKEN")
            +"\n响应url:"+response.request().url()
            + "\n响应body: " + rBody);
    return response;
}
    这里面就是重写的intercept(Chain chain),chain.request和chain.response拿到就可以打印了，这是Chain接口方法：
      public interface Chain {
    public abstract fun call(): okhttp3.Call

    public abstract fun connectTimeoutMillis(): kotlin.Int

    public abstract fun connection(): okhttp3.Connection?

    public abstract fun proceed(request: okhttp3.Request): okhttp3.Response

    public abstract fun readTimeoutMillis(): kotlin.Int

    public abstract fun request(): okhttp3.Request

    public abstract fun withConnectTimeout(timeout: kotlin.Int, unit: java.util.concurrent.TimeUnit): okhttp3.Interceptor.Chain

    public abstract fun withReadTimeout(timeout: kotlin.Int, unit: java.util.concurrent.TimeUnit): okhttp3.Interceptor.Chain

    public abstract fun withWriteTimeout(timeout: kotlin.Int, unit: java.util.concurrent.TimeUnit): okhttp3.Interceptor.Chain

    public abstract fun writeTimeoutMillis(): kotlin.Int
}
    拿到保存在本地，然后返回给服务端，这就是一次完整的请求。
    当然还有多类型上传，formbody上传等等。https://square.github.io/okhttp/https
  这是官方网址，可以去看看。