Github user MikeThomsen commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2180#discussion_r166141568
--- Diff:
nifi-nar-bundles/nifi-mongodb-bundle/nifi-mongodb-processors/src/main/java/org/apache/nifi/processors/mongodb/RunMongoAggregation.java
---
@@ -0,0 +1,203 @@
+/*
+ * 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.processors.mongodb;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.client.AggregateIterable;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.MongoCursor;
+import org.apache.nifi.annotation.behavior.EventDriven;
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.components.Validator;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.bson.conversions.Bson;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+@Tags({"mongo", "aggregation", "aggregate"})
+@CapabilityDescription("A processor that runs an aggregation query
whenever a flowfile is received.")
+@InputRequirement(InputRequirement.Requirement.INPUT_ALLOWED)
+@EventDriven
+public class RunMongoAggregation extends AbstractMongoProcessor {
+
+ private final static Set<Relationship> relationships;
+ private final static List<PropertyDescriptor> propertyDescriptors;
+
+ static final Relationship REL_ORIGINAL = new Relationship.Builder()
+ .description("The input flowfile gets sent to this
relationship when the query succeeds.")
+ .name("original")
+ .build();
+ static final Relationship REL_FAILURE = new Relationship.Builder()
+ .description("The input flowfile gets sent to this
relationship when the query fails.")
+ .name("failure")
+ .build();
+ static final Relationship REL_RESULTS = new Relationship.Builder()
+ .description("The result set of the aggregation will be sent
to this relationship.")
+ .name("results")
+ .build();
+
+ static final List<Bson> buildAggregationQuery(String query) throws
IOException {
+ List<Bson> result = new ArrayList<>();
+
+ ObjectMapper mapper = new ObjectMapper();
+ List<Map> values = mapper.readValue(query, List.class);
+ for (Map val : values) {
+ result.add(new BasicDBObject(val));
+ }
+
+ return result;
+ }
+
+ public static final Validator AGG_VALIDATOR = (subject, value,
context) -> {
+ final ValidationResult.Builder builder = new
ValidationResult.Builder();
+ builder.subject(subject).input(value);
+
+ if (context.isExpressionLanguageSupported(subject) &&
context.isExpressionLanguagePresent(value)) {
+ return builder.valid(true).explanation("Contains Expression
Language").build();
+ }
+
+ String reason = null;
+ try {
+ buildAggregationQuery(value);
+ } catch (final RuntimeException | IOException e) {
+ reason = e.getLocalizedMessage();
+ }
+
+ return builder.explanation(reason).valid(reason == null).build();
+ };
+
+ static final PropertyDescriptor QUERY = new
PropertyDescriptor.Builder()
+ .name("mongo-agg-query")
+ .displayName("Query")
+ .expressionLanguageSupported(true)
+ .description("The aggregation query to be executed.")
+ .required(true)
+ .addValidator(AGG_VALIDATOR)
+ .build();
+
+ static {
+ List<PropertyDescriptor> _propertyDescriptors = new ArrayList<>();
+ _propertyDescriptors.addAll(descriptors);
+ _propertyDescriptors.add(CHARSET);
+ _propertyDescriptors.add(QUERY);
+ _propertyDescriptors.add(QUERY_ATTRIBUTE);
+ _propertyDescriptors.add(BATCH_SIZE);
+ _propertyDescriptors.add(RESULTS_PER_FLOWFILE);
+ _propertyDescriptors.add(SSL_CONTEXT_SERVICE);
+ _propertyDescriptors.add(CLIENT_AUTH);
+ propertyDescriptors =
Collections.unmodifiableList(_propertyDescriptors);
+
+ final Set<Relationship> _relationships = new HashSet<>();
+ _relationships.add(REL_RESULTS);
+ _relationships.add(REL_ORIGINAL);
+ _relationships.add(REL_FAILURE);
+ relationships = Collections.unmodifiableSet(_relationships);
+ }
+
+ @Override
+ public Set<Relationship> getRelationships() {
+ return relationships;
+ }
+
+ @Override
+ public final List<PropertyDescriptor>
getSupportedPropertyDescriptors() {
+ return propertyDescriptors;
+ }
+
+ static String buildBatch(List batch) {
+ ObjectMapper mapper = new ObjectMapper();
+ String retVal;
+ try {
+ retVal = mapper.writeValueAsString(batch.size() > 1 ? batch :
batch.get(0));
+ } catch (Exception e) {
+ retVal = null;
+ }
+
+ return retVal;
+ }
+
+ @Override
+ public void onTrigger(ProcessContext context, ProcessSession session)
throws ProcessException {
+ FlowFile flowFile = session.get();
--- End diff --
I assume you mean this:
```
FlowFile fileToProcess = null;
if (context.hasIncomingConnection()) {
fileToProcess = session.get();
if (fileToProcess == null) {
// Incoming connection with no flow file available, do no work (see
capability description)
return;
}
}
```
Seems easy enough.
---
