Github user markap14 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2123#discussion_r138083515
--- Diff:
nifi-nar-bundles/nifi-standard-services/nifi-mongodb-services-bundle/nifi-mongodb-services/src/main/java/org/apache/nifi/mongodb/MongoDBLookupService.java
---
@@ -0,0 +1,116 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.mongodb;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnEnabled;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.controller.ControllerServiceInitializationContext;
+import org.apache.nifi.lookup.LookupFailureException;
+import org.apache.nifi.lookup.LookupService;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.reporting.InitializationException;
+import org.bson.Document;
+import org.codehaus.jackson.map.ObjectMapper;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+
+
+@Tags({"mongo", "mongodb", "lookup", "record"})
+@CapabilityDescription(
--- End diff --
I think I understand how this service works from looking through the code.
However, I feel the documentation may be a bit lacking for those unable to read
through the code. It would help, I think, to describe a bit more about how to
use it. I think that the coordinates passed in are key/value pairs that will be
sent to MongoDB as a query. And the result that will be returned is whatever
Object is returned by MongoDB for the field whose name is specified by the 'The
key from the result to return' property. Is that right? Perhaps adding an
`additionalDetails.html` that shows an example would be useful.
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