refactor: simplify EntityProcessor

This patch ...

... simplifies the EntityProcessor by replacing ambiguous method names
and logic.

... removes the EntityProcessorTest, because all the tests are already
part of ODataUpdateEntityTest, ODataCreateEntityTest,
ODataDeleteEntityTest and ODataReadEntityTest.

... improves error handling in ODataEndpointHandler, by setting the
correct status code in case that the error is of type
ODataApplicationException.

src/main/java/io/neonbee/internal/handler/ODataEndpointHandler.java

@@ -33,6 +33,7 @@
 import org.apache.olingo.commons.api.http.HttpHeader;
 import org.apache.olingo.commons.api.http.HttpMethod;
 import org.apache.olingo.server.api.OData;
+import org.apache.olingo.server.api.ODataApplicationException;
 import org.apache.olingo.server.api.ODataHandler;
 import org.apache.olingo.server.api.ODataLibraryException;
 import org.apache.olingo.server.api.ODataRequest;
@@ -306,7 +307,8 @@ public void handle(RoutingContext routingContext) {
         }, asyncODataResponse -> {
             // failed to map / process OData request, so fail the web request
             if (asyncODataResponse.failed()) {
-                routingContext.fail(-1, asyncODataResponse.cause());
+                Throwable cause = asyncODataResponse.cause();
+                routingContext.fail(evaluateStatusCode(cause), cause);
                 return;
             }
 
@@ -316,20 +318,25 @@ public void handle(RoutingContext routingContext) {
             processPromise.future().onComplete(asyncResult -> {
                 // (asynchronously) retrieving the odata response failed, so fail the web request
                 if (asyncResult.failed()) {
-                    routingContext.fail(-1, asyncResult.cause());
+                    Throwable cause = asyncResult.cause();
+                    routingContext.fail(evaluateStatusCode(cause), cause);
                     return;
                 }
 
                 try {
                     // map the odataResponse to the routingContext.response
                     mapODataResponse(odataResponse, routingContext.response());
                 } catch (IOException | ODataRuntimeException e) {
-                    routingContext.fail(e);
+                    routingContext.fail(-1, e);
                 }
             });
         });
     }
 
+    private static int evaluateStatusCode(Throwable t) {
+        return t instanceof ODataApplicationException ? ((ODataApplicationException) t).getStatusCode() : -1;
+    }
+
     /**
      * Maps a Vert.x RoutingContext into a new ODataRequest.
      *

src/main/java/io/neonbee/internal/processor/CountEntityCollectionProcessor.java

@@ -117,7 +117,7 @@ public void readEntityCollection(ODataRequest request, ODataResponse response, U
                     } catch (ODataException e) {
                         processPromise.fail(e);
                     }
-                }).onFailure(e -> processPromise.fail(e));
+                }).onFailure(processPromise::fail);
             } catch (ODataException e) {
                 processPromise.fail(e);
             }