android OkHttp3.0

android OkHttp3.0

OkHttp是一个高效的HTTP库:
1.支持 SPDY ，共享同一个Socket来处理同一个服务器的所有请求
2.如果SPDY不可用，则通过连接池来减少请求延时
3.无缝的支持GZIP来减少数据流量
4.缓存响应数据来减少重复的网络请求
优点：
OkHttp会从很多常用的连接问题中自动恢复。如果您的服务器配置了多个IP地址，当第一个IP连接失败的时候，会自动尝试下一个IP。OkHttp还处理了代理服务器问题和SSL握手失败问题。
使用 OkHttp 无需重写您程序中的网络代码。OkHttp实现了几乎和java.net.HttpURLConnection一样的API。如果您用了 Apache HttpClient，则OkHttp也提供了一个对应的okhttp-apache 模块
Okhttp的基本使用，从以下五方面讲解：

1、Get请求(同步和异步)
2、POST请求表单(key-value)
3、POST请求提交(JSON/String/文件等)（这个有待研究）
4、文件下载
5、请求超时设置

添加库依赖
compile 'com.squareup.okhttp3:okhttp:3.4.1'
compile 'com.github.franmontiel:PersistentCookieJar:v0.9.3'  // Cookies持久化库
compile 'com.squareup.okhttp3:logging-interceptor:3.4.1'

1、GET
//同步GET请求
OkHttpClient client = new OkHttpClient();
String run(String url) throws IOException {
  Request request = new Request.Builder().url(url).build();
  Response response = client.newCall(request).execute();
  return response.body().string();
}

//异步GET请求
OkHttpClient client=new OkHttpClient();
Request request = new Request.Builder().url(url).build();
client.newCall(request).enqueue(new Callback() {
  @Override
  public void onFailure(Request request, IOException e) {}

  @Override
  public void onResponse(Response response) throws IOException {}
});

2、POST
public static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");
OkHttpClient client = new OkHttpClient();
String post(String url, String json) throws IOException {
  RequestBody body = RequestBody.create(JSON, json);
  Request request = new Request.Builder()
      .url(url)
      .post(body)
      .build();
  Response response = client.newCall(request).execute();
  return response.body().string();
}

3、异步调用
使用enqueue方法，将call放入请求队列，然后okHttp会在线程池中进行网络访问
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder().url("https://github.com").build();
client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
    }
    @Override
    public void onResponse(Call call, Response response) throws IOException {
       Log.d("onResponse", "response.body(): "+response.body().string());
    }
});

4、HTTP头部的设置和读取
HTTP 头的数据结构是 Map> 类型。对于每个HTTP头，可能有多个值。但是大部分HTTP头都只有一个值，只有少部分HTTP头允许多个值。OkHttp的处理方式是：
Request:
header(name,value) 来设置HTTP头的唯一值
addHeader(name,value) 来补充新值
Response:
header(name) 读取唯一值或多个值的最后一个值
headers(name) 获取所有值
//
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        .url("https://github.com")
        .header("User-Agent", "super agent")
        .addHeader("Accept", "text/html")
        .build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) {
    throw new IOException("error: " + response);
}
System.out.println(response.header("Server"));
System.out.println(response.headers("Set-Cookie"));

5、表单提交
RequestBody formBody = new FormEncodingBuilder()
            .add("query", "Hello")
            .build();

6、文件上传
指定 MultipartBuilder.FORM 类型并通过addPart方法添加不同的Part（每个Part由Header和RequestBody两部分组成），最后调用builde()方法构建一个RequestBody。
MediaType MEDIA_TYPE_TEXT = MediaType.parse("text/plain");
RequestBody requestBody = new MultipartBuilder()
    .type(MultipartBuilder.FORM)
    .addPart(
            Headers.of("Content-Disposition", "form-data; name=\"title\""),
            RequestBody.create(null, "input txt"))
    .addPart(
            Headers.of("Content-Disposition", "form-data; name=\"file\""),
            RequestBody.create(MEDIA_TYPE_TEXT, new File("input.txt")))
    .build();

7、使用流的方式发送POST请求
OkHttpClient client = new OkHttpClient();
final MediaType MEDIA_TYPE_TEXT = MediaType.parse("text/plain");
final String postBody = "Hello World";

RequestBody requestBody = new RequestBody() {
    @Override
    public MediaType contentType() {
        return MEDIA_TYPE_TEXT;
    }
    @Override
    public void writeTo(BufferedSink sink) throws IOException {
        sink.writeUtf8(postBody);
    }
    @Override
    public long contentLength() throws IOException {
        return postBody.length();
    }
};

Request request = new Request.Builder()
        .url("http://www.baidu.com")
        .post(requestBody)
        .build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) {
    throw new IOException("eror: " + response);
}
System.out.println(response.body().string());

8、缓存控制CacheControl
Request request = new Request.Builder()
    .cacheControl(new CacheControl.Builder().noCache().build()) // 强制不缓存
    .url("http://publicobject.com/helloworld.txt")
    .build();

Request request = new Request.Builder()
    .cacheControl(new CacheControl.Builder().maxAge(0, TimeUnit.SECONDS).build()) // 缓存策略由服务器指定
    .url("http://publicobject.com/helloworld.txt")
    .build();

Request request = new Request.Builder()
    .cacheControl(new CacheControl.Builder().onlyIfCached().build()) //强制缓存
    .url("http://publicobject.com/helloworld.txt")
    .build();

Response forceCacheResponse = client.newCall(request).execute();
if (forceCacheResponse.code() != 504) {
  // The resource was cached! Show it.
} else {
  // The resource was not cached.
}

Request request = new Request.Builder()
    .cacheControl(new CacheControl.Builder().maxStale(365, TimeUnit.DAYS).build()) // 允许使用旧的缓存
    .url("http://publicobject.com/helloworld.txt")
    .build();

9、拦截器：可以监视，重写（重写请求、重写响应）和重试
拦截器可以注册为应用拦截器和网络拦截器
应用拦截器：
不需要关心像重定向和重试这样的中间响应
总是调用一次，即使HTTP响应从缓存中获取服务
监视应用原始意图。不关心OkHttp注入的像If-None-Match头
允许短路并不调用Chain.proceed()
允许重试并执行多个Chain.proceed()调用

网络拦截器：
可以操作像重定向和重试这样的中间响应
对于短路网络的缓存响应不会调用
监视即将要通过网络传输的数据
访问运输请求的Connection
重写请求

//重写响应
private static final Interceptor interceptor = new Interceptor() {
  @Override public Response intercept(Interceptor.Chain chain) throws IOException {
    Response originalResponse = chain.proceed(chain.request());
    return originalResponse.newBuilder()
        .header("Cache-Control", "max-age=60")
        .build();
  }
};

OkHttpClient client = new OkHttpClient.Builder()
              .addInterceptor(new HttpLoggingInterceptor() // 应用拦截器
              .addNetworkInterceptor(interceptor) // 网络拦截器
              .setLevel(HttpLoggingInterceptor.Level.BODY))
              .build();           

10、缓存设置
File cacheDirectory = new File(getApplicationContext().getCacheDir().getAbsolutePath(), "Cache"); 
Cache cache = new Cache(cacheDirectory, 10 * 1024 * 1024)); // 创建缓存类

OkHttpClient client = new OkHttpClient.Builder()
      .retryOnConnectionFailure(true)
      .connectTimeout(15, TimeUnit.SECONDS) // 连接超时设置
      .readTimeout(10,TimeUnit.SECONDS); // 读超时设置
      .writeTimeout(10,TimeUnit.SECONDS); // 写超时设置
      .cache(cache) // 设置缓存，okhttp默认是没有缓存,且没有缓存目录的
      .build();

9、Cookies缓存：由CookieJar统一管理Cookies，只需要对OkHttpClient的cookieJar进行设置即可
OkHttpClient mHttpClient = new OkHttpClient.Builder().cookieJar(new CookieJar() {
    private final HashMap> cookieStore = new HashMap<>();
    @Override
    public void saveFromResponse(HttpUrl url, List cookies) {
        cookieStore.put(url.host(), cookies);
    }
    @Override
    public List loadForRequest(HttpUrl url) {
        List cookies = cookieStore.get(url.host());
        return cookies != null ? cookies : new ArrayList();
    }
}).build();

10、Cookies持久化：PersistentCookieJar
ClearableCookieJar cookieJar = new PersistentCookieJar(new SetCookieCache(), new SharedPrefsCookiePersistor(context));
OkHttpClient okHttpClient = new OkHttpClient.Builder()
             .cookieJar(cookieJar)
             .build();