给OkHttpClient添加统一的参数

添加统一的请求参数、请求头 ：是通过拦截器来完成的：

拦截器：

 private Interceptor netCacheInterceptor = new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Request request = chain.request();
            HttpUrl httpUrl = request.url()
                    .newBuilder()
                    // add common parameter
                    .addQueryParameter("token", "123")
                    .addQueryParameter("username", "xiaocai")
                    .build();
            Request build = request.newBuilder()
                    // add common header
                    .addHeader("contentType", "text/json")
                    .url(httpUrl)
                    .build();
            Response response = chain.proceed(build);
            return response;
        }
    };

Request：是一个builder模式，执行的是product的角色。而其中的builder承担着builder、concreteBuilder、director的角色。
chain是okhttp的网络请求者，可以获取request以及发起请求process

okhttp添加拦截器：

    private void initOkHttpClient() {
        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        if (ApiClient.DEBUG) {
            // Log信息拦截器
            HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
            loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
            //设置 Debug Log 模式
            builder.addNetworkInterceptor(loggingInterceptor);
        }
        //设置超时
        builder.connectTimeout(15, TimeUnit.SECONDS);
        builder.readTimeout(20, TimeUnit.SECONDS);
        builder.writeTimeout(20, TimeUnit.SECONDS);
        //错误重连
        builder.retryOnConnectionFailure(true);
        // commen parameter
        builder.addInterceptor(netCacheInterceptor);
        mOkHttpClient = builder.build();
    }

服务器代码：

  @Override
   protected void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       Enumeration parameterNames = request.getParameterNames();
       while(parameterNames.hasMoreElements()){
           String nextElement = parameterNames.nextElement();
           String value = request.getParameter(nextElement);
           System.out.println("nextElement:"+nextElement+" value:"+value);
       }
       
       Enumeration headerNames = request.getHeaderNames();
       while(headerNames .hasMoreElements()){
           String nextElement = headerNames.nextElement();
           String header = request.getHeader(nextElement);
           System.out.println("key:"+nextElement+" value:"+header);
       }
       
   }

服务器得到的结果：

nextElement:username value:xiaocai
nextElement:token value:123
nextElement:loginPassword value:1
nextElement:mobile value:1
key:contenttype value:text/json
key:content-type value:application/x-www-form-urlencoded
key:content-length value:62
key:host value:10.0.2.2:8080
key:connection value:Keep-Alive
key:accept-encoding value:gzip
key:user-agent value:okhttp/3.6.0