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: [NIFI-6798](https://issues.apache.org/jira/browse/NIFI-6798) ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
