OLINGO-738: Adding upsertEntity feature for the server-extension framework

lib/server-core-ext/src/main/java/org/apache/olingo/server/core/ServiceHandler.java

@@ -101,6 +101,21 @@ public interface ServiceHandler extends Processor {
   void updateEntity(DataRequest request, Entity entity, boolean merge, String entityETag,
       EntityResponse response) throws ODataLibraryException, ODataApplicationException;
 
+  /**
+   * Update or create the entity object. If based on passed in entity object's key value,  if 
+   * entity exists update the entity, else create a new entity
+   * @param request
+   * @param entity - Entity to create or update
+   * @param merge - in the case of update, true to do merge operation with current entity, 
+   * false the entity needs to be replaced
+   * @param entityETag - previous entity tag if provided by the user. "*" means allow.
+   * @param response
+   * @throws ODataLibraryException
+   * @throws ODataApplicationException
+   */
+  void upsertEntity(DataRequest request, Entity entity, boolean merge, String entityETag,
+      EntityResponse response) throws ODataLibraryException, ODataApplicationException;
+
   /**
    * Delete the Entity
    * @param request

lib/server-core-ext/src/main/java/org/apache/olingo/server/core/legacy/ProcessorServiceHandler.java

@@ -430,4 +430,11 @@ public class ProcessorServiceHandler implements ServiceHandler {
     throw new ODataHandlerException("not implemented",
         ODataHandlerException.MessageKeys.FUNCTIONALITY_NOT_IMPLEMENTED);
   }
+
+  @Override
+  public void upsertEntity(DataRequest request, Entity entity, boolean merge, String entityETag, 
+      EntityResponse response) throws ODataLibraryException, ODataApplicationException {
+    throw new ODataHandlerException("not implemented",
+        ODataHandlerException.MessageKeys.FUNCTIONALITY_NOT_IMPLEMENTED);
+  }
 }

lib/server-core-ext/src/main/java/org/apache/olingo/server/core/requests/DataRequest.java

@@ -317,7 +317,7 @@ public class DataRequest extends ServiceRequest {
               getContextURL(odata), false, response, getReturnRepresentation());
           handler.createEntity(DataRequest.this, getEntityFromClient(), entityResponse);
         } else {
-          handler.updateEntity(DataRequest.this, getEntityFromClient(), isPATCH(), getETag(),
+          handler.upsertEntity(DataRequest.this, getEntityFromClient(), isPATCH(), getETag(),
               entityResponse);
         }
       } else if (isPOST()) {

lib/server-core-ext/src/test/java/org/apache/olingo/server/example/TripPinHandler.java

@@ -544,4 +544,16 @@ public class TripPinHandler implements ServiceHandler {
   public void crossJoin(DataRequest dataRequest, List<String> entitySetNames, ODataResponse response) {
     response.setStatusCode(200);
   }
+
+  @Override
+  public void upsertEntity(DataRequest request, Entity entity, boolean merge, String entityETag, 
+      EntityResponse response) throws ODataLibraryException, ODataApplicationException {
+    EdmEntitySet edmEntitySet = request.getEntitySet();
+    Entity currentEntity = this.dataModel.getEntity(edmEntitySet.getName(), request.getKeyPredicates());
+    if(currentEntity == null) {
+      createEntity(request, entity, response);
+    } else {
+      updateEntity(request, entity, merge, entityETag, response);
+    }
+  }
 }