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Subject [GitHub] [nifi] turcsanyip commented on a change in pull request #3774: NIFI-6729 - Created AbstractSingleAttributeBasedControllerServiceLook…
Date Tue, 22 Oct 2019 17:02:15 GMT
turcsanyip commented on a change in pull request #3774: NIFI-6729 - Created AbstractSingleAttributeBasedControllerServiceLook…
URL: https://github.com/apache/nifi/pull/3774#discussion_r337638638
 
 

 ##########
 File path: nifi-nar-bundles/nifi-extension-utils/nifi-service-utils/src/main/java/org/apache/nifi/service/lookup/AbstractSingleAttributeBasedControllerServiceLookup.java
 ##########
 @@ -0,0 +1,162 @@
+/*
+ * 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 andf
+ * limitations under the License.
+ */
+package org.apache.nifi.service.lookup;
+
+import org.apache.nifi.annotation.lifecycle.OnDisabled;
+import org.apache.nifi.annotation.lifecycle.OnEnabled;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.controller.AbstractControllerService;
+import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.controller.ControllerService;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * A lookup ControllerService that can choose one (from probably multiple) ControllerServices
of the given type {@link S}.
+ * <p>
+ * Selection is based on a single {@linkplain String} lookup key.
+ * <p>
+ * Lookup key is provided as a value in an attribute map (usually coming form a flowfile)
+ * with a predefined key (see {@link #lookupAttribute()}).
+ *
+ * @param <S> The type of service to be looked up
+ */
+public abstract class AbstractSingleAttributeBasedControllerServiceLookup<S extends ControllerService>
extends AbstractControllerService {
+    protected volatile Map<String, S> serviceMap;
+
+    /**
+     * @return the Class that represents the type of service that will be returned by {@link
#lookupService(Map)}
+     */
+    public abstract Class<S> getServiceType();
+
+    /**
+     * @return the name of attribute (usually from a flowfile) the value of which serves
as the lookup key
+     * for the desired service (of type {@link S})
+     */
+    protected abstract String lookupAttribute();
+
+    /**
+     * Returns a ControllerService (of type {@link S}) based on the provided attributes map
(usually by retrieving
+     *  a lookup attribute from it via {@link #lookupAttribute()} and use it to identify
the appropriate service).
+     * @param attributes Map containing the lookup attribute based on which ControllerService
is chosen
+     * @return the chosen ControllerService
+     */
+    public S lookupService(Map<String, String> attributes) {
+        if (attributes == null) {
+            throw new ProcessException("Attributes map is null");
+        } else if (!attributes.containsKey(lookupAttribute())) {
+            throw new ProcessException("Attributes must contain an attribute name '" + lookupAttribute()
+ "'");
+        }
+
+        Object lookupKey = Optional.of(lookupAttribute())
+                .map(attributes::get)
+                .orElseThrow(() -> new ProcessException(lookupAttribute() + " cannot be
null or blank"));
+
+        S service = serviceMap.get(lookupKey);
+
+        if (service == null) {
+            throw new ProcessException("No " + getServiceName() + " found for " + lookupAttribute());
+        }
+
+        return service;
+    }
+
+    @OnEnabled
+    public void onEnabled(final ConfigurationContext context) {
+        Map<String, S> serviceMap = new HashMap<>();
+
+        context.getProperties().keySet().stream()
+                .filter(PropertyDescriptor::isDynamic)
+                .forEach(propertyDescriptor -> {
+                    S service = context.getProperty(propertyDescriptor).asControllerService(getServiceType());
+
+                    serviceMap.put(propertyDescriptor.getName(), service);
+                });
+
+        this.serviceMap = Collections.unmodifiableMap(serviceMap);
+    }
+
+    @OnDisabled
+    public void onDisabled() {
+        serviceMap = null;
+    }
+
+    @Override
+    protected PropertyDescriptor getSupportedDynamicPropertyDescriptor(final String propertyDescriptorName)
{
+        return lookupKeyPropertyDescriptor(propertyDescriptorName);
+    }
+
+    @Override
+    protected Collection<ValidationResult> customValidate(ValidationContext context)
{
 
 Review comment:
   [https://issues.apache.org/jira/browse/NIFI-6798](url)

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