一. retrofit的簡(jiǎn)單使用

先看下涉及到的類:

首先定義個(gè)接口ApiService,所有的請(qǐng)求方法的定義.

public interface ApiService {

    @POST("doPost")
    Call<ResponseBody> doPost(@Query("name") String name,
                              @Query("email") String e
    );

    @GET("doGet")
    Call<ResponseBody> doGet(@Query("name") String name,
               @Query("age") int age
    );
}

對(duì)retrofit的配置類,不建議每次都去創(chuàng)建retrofit的實(shí)例. OkHttpClient 也要保證整個(gè)工程只有一個(gè)實(shí)例,官方推薦也是這么做的.

/**
 * Created by CaiRR on 2017-10-25.
 */

public class ApiClient {
    private static OkHttpClient mOkHttpClient = null;
    private static Retrofit mRetrofit;
    private static ApiService mApiService;
    private static final boolean isDebug = true;
    private static final String HTTP_BASE_URL = "http://192.168.6.21:9090";

    public static ApiClient getInstance() {
        return SingletonHolder.INSTANCE;
    }

    private static class SingletonHolder {
        private static final ApiClient INSTANCE = new ApiClient();
    }

    private ApiClient() {
        initOkHttpClient();
        mRetrofit = new Retrofit.Builder()
                .baseUrl(HTTP_BASE_URL)
                //設(shè)置 Json 轉(zhuǎn)換器
                .addConverterFactory(GsonConverterFactory.create())
                .client(mOkHttpClient)
                .build();
        mApiService = mRetrofit.create(ApiService.class);
    }

    private void initOkHttpClient() {
        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        if (isDebug) {
            // Log信息攔截器
            HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
            loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
            //設(shè)置 Debug Log 模式
            builder.addInterceptor(loggingInterceptor);
        }
        //設(shè)置超時(shí)
        builder.connectTimeout(15, TimeUnit.SECONDS);
        builder.readTimeout(60, TimeUnit.SECONDS);
        builder.writeTimeout(60, TimeUnit.SECONDS);
        //錯(cuò)誤重連
        builder.retryOnConnectionFailure(true);
        mOkHttpClient = builder.build();
    }

    public ApiService getApiService() {
        return mApiService;
    }

    public OkHttpClient getOkhttpClient() {
        if (mOkHttpClient == null) {
            initOkHttpClient();
        }
        return mOkHttpClient;
    }

}

在這里簡(jiǎn)單的使用 post 和 get 請(qǐng)求,分別用同步和異步的形式.

public class TestRetrofitActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test_retrofit);

        findViewById(R.id.btn_get).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                doGet();
            }
        });


        findViewById(R.id.btn_post).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                doPost();
            }
        });
    }

    private void doPost() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Response<ResponseBody> response = ApiClient.getInstance().getApiService().doPost("xiaocai", "xiaocai@163.com").execute();
                    String data = response.body().string();
                    Log.d("xiaocai", data);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    private void doGet() {
        ApiClient.getInstance().getApiService().doGet("xiaocai", 25).enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                try {
                    String data = response.body().string();
                    Log.d("xiaocai", data);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {
                t.printStackTrace();
            }
        });

    }
}

在spring boot中簡(jiǎn)單的做下處理:

@RestController
public class HelloController {
    private final static org.slf4j.Logger log = LoggerFactory.getLogger("xiaocai");

    @RequestMapping("/sayHello")
    public String sayHello() {
        return JsonHelper.success("hello world");
    }

    @GetMapping("/doGet")
    public String testGet(@RequestParam(value = "name") String name,
                          @RequestParam(value = "age", required = false) int age) {
        String data = "name:" + name + " age:" + age;
        log.debug(data);
        return JsonHelper.success(data);
    }

    @PostMapping("/doPost")
    public String testPost(@RequestParam(value = "name") String name,
                          @RequestParam(value = "email", required = false) String email) {
        String data = "name:" + name + " email:" + email;
        log.debug(data);
        return JsonHelper.success(data);
    }
}

日志輸出:

 // post 請(qǐng)求
 D/OkHttp: --> POST http://192.168.6.21:9090/post?name=xiaocai&email=xiaocai@163.com http/1.1
 D/OkHttp: Content-Length: 0
 D/OkHttp: --> END POST (0-byte body)
 D/OkHttp: <-- 200  http://192.168.6.21:9090/post?name=xiaocai&email=xiaocai@163.com (31ms)
 D/OkHttp: Content-Type: text/plain;charset=UTF-8
 D/OkHttp: Content-Length: 82
 D/OkHttp: Date: Wed, 25 Oct 2017 07:43:47 GMT
 D/OkHttp: {"msg":"成功","code":0,"data":"name:xiaocai email:xiaocai@163.com","status":"0"}
 D/OkHttp: <-- END HTTP (82-byte body)
 D/xiaocai: {"msg":"成功","code":0,"data":"name:xiaocai email:xiaocai@163.com","status":"0"}
 
 // get 請(qǐng)求
 D/OkHttp: --> GET http://192.168.6.21:9090/get?name=xiaocai&age=25 http/1.1
 D/OkHttp: --> END GET
 D/OkHttp: <-- 200  http://192.168.6.21:9090/get?name=xiaocai&age=25 (18ms)
 D/OkHttp: Content-Type: text/plain;charset=UTF-8
 D/OkHttp: Content-Length: 67
 D/OkHttp: Date: Wed, 25 Oct 2017 07:44:13 GMT
 D/OkHttp: {"msg":"成功","code":0,"data":"name:xiaocai age:25","status":"0"}
 D/OkHttp: <-- END HTTP (67-byte body)
 D/xiaocai: {"msg":"成功","code":0,"data":"name:xiaocai age:25","status":"0"}

整個(gè)過(guò)程還是比較清爽的.

其他的使用方式可以直接看官網(wǎng)的說(shuō)明:
retrofit的使用

二. 源碼分析

我們?cè)谑褂?retrofit 的時(shí)候,基本上都會(huì):

  mRetrofit = new Retrofit.Builder()
          .baseUrl(HTTP_BASE_URL)
          //設(shè)置 Json 轉(zhuǎn)換器
          .addConverterFactory(GsonConverterFactory.create())
          .client(mOkHttpClient)
          .build();
  mApiService = mRetrofit.create(ApiService.class);

從 create 方法作為入口進(jìn)行分析:

  public <T> T create(final Class<T> service) {
    Utils.validateServiceInterface(service); // 校驗(yàn)是否為接口且不能繼承接口
    if (validateEagerly) {
      eagerlyValidateMethods(service); 
    }
    // 使用動(dòng)態(tài)代理
    return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[] { service },
        new InvocationHandler() {
          private final Platform platform = Platform.get();

          // 每次請(qǐng)求都會(huì)走(執(zhí)行方法)
          @Override public Object invoke(Object proxy, Method method, @Nullable Object[] args)
              throws Throwable {
            // If the method is a method from Object then defer to normal invocation.
            if (method.getDeclaringClass() == Object.class) { // 校驗(yàn)
              return method.invoke(this, args);
            }
            if (platform.isDefaultMethod(method)) { // 校驗(yàn)平臺(tái)
              return platform.invokeDefaultMethod(method, service, proxy, args);
            }
            
            // 處理接口中定義的方法,serviceMethod解析注解
            ServiceMethod<Object, Object> serviceMethod =
                (ServiceMethod<Object, Object>) loadServiceMethod(method);
            // args 是具體的參數(shù)值
            OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args); 
            return serviceMethod.callAdapter.adapt(okHttpCall);
          }
        });
  }
  
  // 里面涉及解析接口中定義的單個(gè)方法
  ServiceMethod<?, ?> loadServiceMethod(Method method) {
    ServiceMethod<?, ?> result = serviceMethodCache.get(method);
    if (result != null) return result; // 使用緩存

    synchronized (serviceMethodCache) {
      result = serviceMethodCache.get(method);
      if (result == null) { // 雙重檢查加鎖
        result = new ServiceMethod.Builder<>(this, method).build();  // 創(chuàng)建 ServiceMethod 類
        serviceMethodCache.put(method, result); // 加入到緩存中
      }
    }
    return result;
  }

1. ServiceMethod 分析

ServiceMethod 的主要職責(zé)是將接口中的單個(gè)方法解析為 HTTP call ,里面涉及到解析請(qǐng)求方式,請(qǐng)求參數(shù).
需要注意的是 ServiceMethod 處理的單個(gè)接口中的方法.``````
ServiceMethod 是通過(guò) builder 模式創(chuàng)建的

    public Builder(Retrofit retrofit, Method method) {
      this.retrofit = retrofit;
      this.method = method;
      this.methodAnnotations = method.getAnnotations(); // 獲取方法上的注解
      this.parameterTypes = method.getGenericParameterTypes(); // 參數(shù)類型
      this.parameterAnnotationsArray = method.getParameterAnnotations(); // 獲取參數(shù)中的注解及注解中的內(nèi)容
    }

以下方法為例,主要研究方法上的注解及其值和解析方法參數(shù)的注解和值

    @POST("post")
    Call<ResponseBody> doPost(@Query("name") String name,
                              @Query("email") String email
    );

methodAnnotations 中會(huì)得到 @retrofit2.http.POST(value=doPost) ,如果多個(gè)修飾這里也會(huì)得到多個(gè)注解類
parameterTypes 會(huì)得到 java.lang.String 和 java.lang.String 分別對(duì)應(yīng)兩個(gè)參數(shù)的類型
parameterAnnotationsArray 中會(huì)得到 類型是 Query 其值是 name,類型是 Query 其值是 email,這里的值是注解內(nèi)的值.

在 build 中會(huì)去解析注解:

      int parameterCount = parameterAnnotationsArray.length;
      parameterHandlers = new ParameterHandler<?>[parameterCount];
      for (int p = 0; p < parameterCount; p++) {
        Type parameterType = parameterTypes[p];
        if (Utils.hasUnresolvableType(parameterType)) { // 校驗(yàn)方法中的參數(shù)類型
          throw parameterError(p, "Parameter type must not include a type variable or wildcard: %s",
              parameterType);
        }

        Annotation[] parameterAnnotations = parameterAnnotationsArray[p]; // 解析方法中的參數(shù)
        if (parameterAnnotations == null) {
          throw parameterError(p, "No Retrofit annotation found.");
        }

        parameterHandlers[p] = parseParameter(p, parameterType, parameterAnnotations); // 解析方法上的注解及注解值
      }

解析方法上的注解:

    private void parseMethodAnnotation(Annotation annotation) {
      // 判斷請(qǐng)求類型
      if (annotation instanceof DELETE) {
        parseHttpMethodAndPath("DELETE", ((DELETE) annotation).value(), false);
      } else if (annotation instanceof GET) {
        parseHttpMethodAndPath("GET", ((GET) annotation).value(), false);
      } else if (annotation instanceof HEAD) {
        parseHttpMethodAndPath("HEAD", ((HEAD) annotation).value(), false);
        if (!Void.class.equals(responseType)) {
          throw methodError("HEAD method must use Void as response type.");
        }
      } else if (annotation instanceof PATCH) {
        parseHttpMethodAndPath("PATCH", ((PATCH) annotation).value(), true);
      } else if (annotation instanceof POST) {
        parseHttpMethodAndPath("POST", ((POST) annotation).value(), true);
      } else if (annotation instanceof PUT) {
        parseHttpMethodAndPath("PUT", ((PUT) annotation).value(), true);
      } else if (annotation instanceof OPTIONS) {
        parseHttpMethodAndPath("OPTIONS", ((OPTIONS) annotation).value(), false);
      } else if (annotation instanceof HTTP) {
        HTTP http = (HTTP) annotation;
        parseHttpMethodAndPath(http.method(), http.path(), http.hasBody());
      } else if (annotation instanceof retrofit2.http.Headers) {
        String[] headersToParse = ((retrofit2.http.Headers) annotation).value();
        if (headersToParse.length == 0) {
          throw methodError("@Headers annotation is empty.");
        }
        headers = parseHeaders(headersToParse);
      } else if (annotation instanceof Multipart) {
        if (isFormEncoded) {
          throw methodError("Only one encoding annotation is allowed.");
        }
        isMultipart = true;
      } else if (annotation instanceof FormUrlEncoded) {
        if (isMultipart) {
          throw methodError("Only one encoding annotation is allowed.");
        }
        isFormEncoded = true;
      }
    }
    
    
    // 解析方法上的注解參數(shù)值 value:"doPost"
    private void parseHttpMethodAndPath(String httpMethod, String value, boolean hasBody) {
      if (this.httpMethod != null) {
        throw methodError("Only one HTTP method is allowed. Found: %s and %s.",
            this.httpMethod, httpMethod);
      }
      this.httpMethod = httpMethod;
      this.hasBody = hasBody;

      if (value.isEmpty()) {
        return;
      }

      // Get the relative URL path and existing query string, if present.
      int question = value.indexOf('?');
      if (question != -1 && question < value.length() - 1) {
        // Ensure the query string does not have any named parameters.
        String queryParams = value.substring(question + 1);
        Matcher queryParamMatcher = PARAM_URL_REGEX.matcher(queryParams);
        if (queryParamMatcher.find()) {
          throw methodError("URL query string \"%s\" must not have replace block. "
              + "For dynamic query parameters use @Query.", queryParams);
        }
      }

      this.relativeUrl = value;
      this.relativeUrlParamNames = parsePathParameters(value);  // value:"favorite/add"
    }

解析這個(gè)之后會(huì)用到 toRequest 方法中,在 OkHttpCall 中被調(diào)用.

在 parseParameterAnnotation 中會(huì)解析參數(shù)的注解,并構(gòu)建響應(yīng)的注解類型,在這個(gè)例子中會(huì)創(chuàng)建兩個(gè) Query 類. parseParameterAnnotation 中主要做了構(gòu)建對(duì)應(yīng)請(qǐng)求類型的類,這里就不貼代碼了.
簡(jiǎn)單看下其中一個(gè)請(qǐng)求類型的類 Field :

  static final class Query<T> extends ParameterHandler<T> {
    private final String name;// 參數(shù)名
    private final Converter<T, String> valueConverter;
    private final boolean encoded;

    Query(String name, Converter<T, String> valueConverter, boolean encoded) {
      this.name = checkNotNull(name, "name == null");
      this.valueConverter = valueConverter;
      this.encoded = encoded;
    }

    @Override void apply(RequestBuilder builder, T value) throws IOException {
      if (value == null) return; // Skip null values.
      // value:參數(shù)值,例如得到的是"xiaocai"
      builder.addQueryParam(name, valueConverter.convert(value), encoded);
    }
  }
 

我們?cè)賮?lái)看下ServiceMethod對(duì)外提供的方法

ServiceMethod的結(jié)構(gòu)

toRequest 構(gòu)建請(qǐng)求體

  /** Builds an HTTP request from method arguments. */
  Request toRequest(Object... args) throws IOException {
    // 創(chuàng)建請(qǐng)求體
    RequestBuilder requestBuilder = new RequestBuilder(httpMethod, baseUrl, relativeUrl, headers,
        contentType, hasBody, isFormEncoded, isMultipart);

    @SuppressWarnings("unchecked") // It is an error to invoke a method with the wrong arg types.
    ParameterHandler<Object>[] handlers = (ParameterHandler<Object>[]) parameterHandlers;

    int argumentCount = args != null ? args.length : 0;
    if (argumentCount != handlers.length) { // 校驗(yàn)參數(shù)個(gè)數(shù)是否一致
      throw new IllegalArgumentException("Argument count (" + argumentCount
          + ") doesn't match expected count (" + handlers.length + ")");
    }
    
    // 添加請(qǐng)求參數(shù)
    for (int p = 0; p < argumentCount; p++) {
      handlers[p].apply(requestBuilder, args[p]);
    }

    return requestBuilder.build();
  }

toResponse 解析響應(yīng)體

  /** Builds a method return value from an HTTP response body. */
  T toResponse(ResponseBody body) throws IOException {
    return responseConverter.convert(body);
  }

這里就交給轉(zhuǎn)換器去解析請(qǐng)求體,可以看下一個(gè)最簡(jiǎn)單的解析 StringConverter:

  static final class StringConverter implements Converter<String, String> {
    static final StringConverter INSTANCE = new StringConverter();

    @Override public String convert(String value) throws IOException {
      return value;
    }
  }

parsePathParameters 解析參數(shù)

   * Gets the set of unique path parameters used in the given URI. If a parameter is used twice
   * in the URI, it will only show up once in the set.
   */
  static Set<String> parsePathParameters(String path) {
    Matcher m = PARAM_URL_REGEX.matcher(path);
    Set<String> patterns = new LinkedHashSet<>();
    while (m.find()) {
      patterns.add(m.group(1));
    }
    return patterns;
  }

到此我們已經(jīng)已經(jīng)分析完解析接口的操作,其中使用動(dòng)態(tài)代理解析接口,ServiceMethod 中解析單個(gè)接口中的方法的注解.
回到動(dòng)態(tài)代理中,ServiceMethod主要是給OkHttpCall調(diào)用.所以接下來(lái)分析OkHttpCall的作用.

 ServiceMethod serviceMethod = loadServiceMethod(method);
 OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args);
 return serviceMethod.callAdapter.adapt(okHttpCall);

這里調(diào)用了callAdapter中的adapt方法,而 CallAdapter 只是個(gè)接口,我的工程中使用到了rxjava,可以看下其實(shí)現(xiàn).

image.png

挑個(gè)簡(jiǎn)單的來(lái)看 SimpleCallAdapter:

  static final class SimpleCallAdapter implements CallAdapter<Observable<?>> {
    private final Type responseType;
    private final Scheduler scheduler;

    SimpleCallAdapter(Type responseType, Scheduler scheduler) {
      this.responseType = responseType;
      this.scheduler = scheduler;
    }

    @Override public Type responseType() {
      return responseType;
    }

    @Override public <R> Observable<R> adapt(Call<R> call) {
      Observable<R> observable = Observable.create(new CallOnSubscribe<>(call)) //
          .lift(OperatorMapResponseToBodyOrError.<R>instance());
      if (scheduler != null) {
        return observable.subscribeOn(scheduler);
      }
      return observable;
    }
  }

具體的執(zhí)行就到 rxjava 中了,這部分以后在進(jìn)行分析.還是繼續(xù)解析 OkHttpCall 吧.

2. OkHttpCall 解析

OkHttpCall 其實(shí)是對(duì) okhttp 中的 Call 進(jìn)行包裝,真正實(shí)現(xiàn) Call 的還是 okhttp 中的 RealCall.
OkHttpCall 發(fā)起請(qǐng)求的方法:

  @Override public synchronized Request request() {
    okhttp3.Call call = rawCall;
    if (call != null) { // 相當(dāng)于有緩存
      return call.request();
    }
    if (creationFailure != null) { // 創(chuàng)建失敗的情況
      if (creationFailure instanceof IOException) {
        throw new RuntimeException("Unable to create request.", creationFailure);
      } else {
        throw (RuntimeException) creationFailure;
      }
    }
    try {
      // 創(chuàng)建 okhttp3.Call 對(duì)象并發(fā)起請(qǐng)求
      return (rawCall = createRawCall()).request();
    } catch (RuntimeException e) {
      creationFailure = e;
      throw e;
    } catch (IOException e) {
      creationFailure = e;
      throw new RuntimeException("Unable to create request.", e);
    }
  }

創(chuàng)建 okhttp3.Call 對(duì)象

  // 創(chuàng)建 okhttp3.Call 對(duì)象
  private okhttp3.Call createRawCall() throws IOException {
    Request request = serviceMethod.toRequest(args); // 獲取請(qǐng)求體
    // serviceMethod.callFactory 里保存的就是 okhttpclient
    okhttp3.Call call = serviceMethod.callFactory.newCall(request);
    if (call == null) {
      throw new NullPointerException("Call.Factory returned null.");
    }
    return call;
  }

構(gòu)建請(qǐng)求體并發(fā)起請(qǐng)求,其實(shí)就是調(diào)用 okhttpclient 中的響應(yīng)的方法,也就體現(xiàn)了 OkHttpCall 是個(gè)包裝類.

OkHttpCall也分為同步和異步.先看同步請(qǐng)求方法:

  @Override public Response<T> execute() throws IOException {
    okhttp3.Call call;

    synchronized (this) {
      if (executed) throw new IllegalStateException("Already executed.");
      executed = true;

      if (creationFailure != null) {
        if (creationFailure instanceof IOException) {
          throw (IOException) creationFailure;
        } else {
          throw (RuntimeException) creationFailure;
        }
      }

      call = rawCall;
      if (call == null) {
        try {
          call = rawCall = createRawCall();
        } catch (IOException | RuntimeException e) {
          creationFailure = e;
          throw e;
        }
      }
    }

    if (canceled) {
      call.cancel();
    }

    return parseResponse(call.execute()); // 執(zhí)行請(qǐng)求并解析響應(yīng)體
  }

里面大多是校驗(yàn)判斷工作,createRawCall 也就是上面的創(chuàng)建請(qǐng)求體.
最后一行執(zhí)行請(qǐng)求,調(diào)用的是 okhttp3.Call 中的執(zhí)行方法,然后進(jìn)行解析響應(yīng)體:

  Response<T> parseResponse(okhttp3.Response rawResponsy's source (the only stateful object) so we can pass the response along.
                                                           rawResponse = rawRe) throws IOException {
    ResponseBody rawBody = rawResponse.body();

    // Remove the bodesponse.newBuilder()
        .body(new NoContentResponseBody(rawBody.contentType(), rawBody.contentLength()))
        .build();

    int code = rawResponse.code();
    if (code < 200 || code >= 300) { // 請(qǐng)求失敗
      try {
        // Buffer the entire body to avoid future I/O.
        ResponseBody bufferedBody = Utils.buffer(rawBody);
        return Response.error(bufferedBody, rawResponse);  // 返回失敗狀態(tài)的響應(yīng)體
      } finally {
        rawBody.close();
      }
    }

    // 請(qǐng)求成功,但沒(méi)有響應(yīng)體.可以了解下這兩個(gè)狀態(tài)具體代表什么:
    // HTTP 204(no content)表示響應(yīng)執(zhí)行成功铛嘱，但沒(méi)有數(shù)據(jù)返回仅颇，瀏覽器不用刷新度苔，不用導(dǎo)向新頁(yè)面仔粥。
    // HTTP 205(reset content) 表示響應(yīng)執(zhí)行成功，重置頁(yè)面（Form表單）禀酱，方便用戶下次輸入读存。
    if (code == 204 || code == 205) { 
      return Response.success(null, rawResponse);
    }

    ExceptionCatchingRequestBody catchingBody = new ExceptionCatchingRequestBody(rawBody);
    try {
      T body = serviceMethod.toResponse(catchingBody); // 交給 serviceMethod 處理響應(yīng)體
      return Response.success(body, rawResponse); // 返回成功時(shí)的響應(yīng)體
    } catch (RuntimeException e) {
      // If the underlying source threw an exception, propagate that rather than indicating it was
      // a runtime exception.
      catchingBody.throwIfCaught();
      throw e;
    }
  }

還是那句話,OkHttpCall其實(shí)沒(méi)干什么大事,包裝類.

異步請(qǐng)求:

  @Override public void enqueue(final Callback<T> callback) {
    if (callback == null) throw new NullPointerException("callback == null");

    okhttp3.Call call;
    Throwable failure;

    synchronized (this) {
      if (executed) throw new IllegalStateException("Already executed.");
      executed = true;

      call = rawCall;
      failure = creationFailure;
      if (call == null && failure == null) {
        try {
          call = rawCall = createRawCall(); // 構(gòu)建 okhttp3.Call 對(duì)象
        } catch (Throwable t) {
          failure = creationFailure = t;
        }
      }
    }

    if (failure != null) {
      callback.onFailure(this, failure);
      return;
    }

    if (canceled) {
      call.cancel();
    }
    
    // 調(diào)用 okhttp3.Call 對(duì)象的異步請(qǐng)求方法
    call.enqueue(new okhttp3.Callback() {
      @Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse)
          throws IOException {
        Response<T> response;
        try {
          response = parseResponse(rawResponse); // 解析響應(yīng)體
        } catch (Throwable e) {
          callFailure(e);
          return;
        }
        callSuccess(response); // 回調(diào)響應(yīng)成功的方法
      }

      @Override public void onFailure(okhttp3.Call call, IOException e) {
        try {
          callback.onFailure(OkHttpCall.this, e); // 回調(diào)響應(yīng)失敗的方法
        } catch (Throwable t) {
          t.printStackTrace();
        }
      }

      private void callFailure(Throwable e) {
        try {
          callback.onFailure(OkHttpCall.this, e); // 回調(diào)響應(yīng)失敗的方法
        } catch (Throwable t) {
          t.printStackTrace();
        }
      }

      private void callSuccess(Response<T> response) {
        try {
          callback.onResponse(OkHttpCall.this, response); // 回調(diào)響應(yīng)失敗的方法
        } catch (Throwable t) {
          t.printStackTrace();
        }
      }
    });
  }

到此 OkHttpCall 整體已經(jīng)分析完成.

在整體看下 retrofit,涉及的類并不多

整體都是對(duì) okhttp 進(jìn)行封裝,是的調(diào)用起來(lái)更加清爽,而且擴(kuò)展性高,其中的轉(zhuǎn)換器可以自己添加.配合 rxjava 效果更佳.
看源碼時(shí)不僅理解原理,更重要的是學(xué)習(xí)代碼結(jié)構(gòu),看看大神們都是怎樣做封裝/解耦/擴(kuò)展性的.