added asynchronous API

build.gradle

@@ -1,5 +1,5 @@
 group 'io.faob'
-version '0.1.0'
+version '0.2.0'
 
 apply plugin: 'java'
 

src/main/java/io/faob/utopian/handlers/ErrorHandler.java

@@ -0,0 +1,5 @@
+package io.faob.utopian.handlers;
+
+public interface ErrorHandler<E> {
+    void handleError(E e);
+}

src/main/java/io/faob/utopian/handlers/ResponseHandler.java

@@ -0,0 +1,5 @@
+package io.faob.utopian.handlers;
+
+public interface ResponseHandler<T> {
+    void handleResponse(T r);
+}

src/main/java/io/faob/utopian/http/HttpManager.java

@@ -1,6 +1,9 @@
 package io.faob.utopian.http;
 
 
+import io.faob.utopian.handlers.ErrorHandler;
+import io.faob.utopian.handlers.ResponseHandler;
+
 /**
  * Manager that handles http related stuff.
  * <p>Calls can be executed synchronously with {@link #get}, or asynchronously (not implemented yet).
@@ -12,10 +15,20 @@
 public interface HttpManager<T> {
 
     /**
-     * Synchronously send the request and return its response.
+     * Synchronously sends request and return its response.
      *
      * @return Response body type.
      * @throws Exception if a problem occurred talking to the server.
      */
     T get() throws Exception;
+
+
+    /**
+     * Asynchronously sends request and notify {@code responseHandler} on response or
+     * notify {@code errorHandler} when some error occurred.
+     *
+     * @param responseHandler This lambda expression gets called on response
+     * @param errorHandler    This lambda expression gets called on error
+     */
+    void getAsync(ResponseHandler<T> responseHandler, ErrorHandler<Exception> errorHandler);
 }

src/main/java/io/faob/utopian/http/HttpManagerImpl.java

@@ -1,9 +1,11 @@
 package io.faob.utopian.http;
 
+import io.faob.utopian.handlers.ErrorHandler;
+import io.faob.utopian.handlers.ResponseHandler;
 import io.faob.utopian.type.TypeMapper;
-import okhttp3.OkHttpClient;
-import okhttp3.Request;
-import okhttp3.Response;
+import okhttp3.*;
+
+import java.io.IOException;
 
 public class HttpManagerImpl<T> implements HttpManager<T> {
     private String url;
@@ -21,4 +23,25 @@ public T get() throws Exception {
         Response response = okHttpClient.newCall(request).execute();
         return typeMapper.map(response.body().string());
     }
+
+    @Override
+    public void getAsync(ResponseHandler<T> responseHandler, ErrorHandler<Exception> errorHandler) {
+        Request request = new Request.Builder().url(url).build();
+        okHttpClient.newCall(request).enqueue(new Callback() {
+            @Override
+            public void onFailure(Call call, IOException e) {
+                errorHandler.handleError(e);
+            }
+
+            @Override
+            public void onResponse(Call call, Response response) throws IOException {
+                try {
+                    String jsonString = response.body().string();
+                    responseHandler.handleResponse(typeMapper.map(jsonString));
+                } catch (Exception e) {
+                    errorHandler.handleError(e);
+                }
+            }
+        });
+    }
 }