Replace AsyncResponseHandler to ResponseHandler on SynchronousMethodH…

…andler

Eliminates unnecessary overhead caused by CompletableFutre on synchronous operation.

core/src/main/java/feign/SynchronousMethodHandler.java

@@ -22,8 +22,6 @@
 import feign.codec.ErrorDecoder;
 import java.io.IOException;
 import java.util.List;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.CompletionException;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
 
@@ -36,13 +34,12 @@ final class SynchronousMethodHandler implements MethodHandler {
   private final Client client;
   private final Retryer retryer;
   private final List<RequestInterceptor> requestInterceptors;
-  private final ResponseInterceptor responseInterceptor;
   private final Logger logger;
   private final Logger.Level logLevel;
   private final RequestTemplate.Factory buildTemplateFromArgs;
   private final Options options;
   private final ExceptionPropagationPolicy propagationPolicy;
-  private final AsyncResponseHandler asyncResponseHandler;
+  private final ResponseHandler responseHandler;
 
 
   private SynchronousMethodHandler(Target<?> target, Client client, Retryer retryer,
@@ -63,8 +60,7 @@ private SynchronousMethodHandler(Target<?> target, Client client, Retryer retrye
     this.buildTemplateFromArgs = checkNotNull(buildTemplateFromArgs, "metadata for %s", target);
     this.options = checkNotNull(options, "options for %s", target);
     this.propagationPolicy = propagationPolicy;
-    this.responseInterceptor = responseInterceptor;
-    this.asyncResponseHandler = new AsyncResponseHandler(logLevel, logger, decoder, errorDecoder,
+    this.responseHandler = new ResponseHandler(logLevel, logger, decoder, errorDecoder,
         dismiss404, closeAfterDecode, responseInterceptor);
   }
 
@@ -117,22 +113,10 @@ Object executeAndDecode(RequestTemplate template, Options options) throws Throwa
       }
       throw errorExecuting(request, e);
     }
-    long elapsedTime = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);
-
-    CompletableFuture<Object> resultFuture = new CompletableFuture<>();
-    asyncResponseHandler.handleResponse(resultFuture, metadata.configKey(), response,
-        metadata.returnType(), elapsedTime);
 
-    try {
-      if (!resultFuture.isDone())
-        throw new IllegalStateException("Response handling not done");
-      return resultFuture.join();
-    } catch (CompletionException e) {
-      Throwable cause = e.getCause();
-      if (cause != null)
-        throw cause;
-      throw e;
-    }
+    long elapsedTime = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);
+    return responseHandler.handleResponse(
+        metadata.configKey(), response, metadata.returnType(), elapsedTime);
   }
 
   long elapsedTime(long start) {