nifi/nifi-api/src/main/java/org/apache/nifi/components/AbstractConfigurableComponent.java

/*
 * 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.components;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;

public abstract class AbstractConfigurableComponent implements ConfigurableComponent {

    /**
     * Allows subclasses to perform their own validation on the already set
     * properties. Since each property is validated as it is set this allows
     * validation of groups of properties together. Default return is an empty
     * set.
     *
     * This method will be called only when it has been determined that all
     * property values are valid according to their corresponding
     * PropertyDescriptor's validators.
     *
     * @param validationContext provides a mechanism for obtaining externally
     * managed values, such as property values and supplies convenience methods
     * for operating on those values
     *
     * @return Collection of ValidationResult objects that will be added to any
     * other validation findings - may be null
     */
    protected Collection<ValidationResult> customValidate(final ValidationContext validationContext) {
        return Collections.emptySet();
    }

    /**
     * Returns a PropertyDescriptor for the name specified that is fully
     * populated
     *
     * @param descriptorName
     * @return
     */
    @Override
    public final PropertyDescriptor getPropertyDescriptor(final String descriptorName) {
        final PropertyDescriptor specDescriptor = new PropertyDescriptor.Builder().name(descriptorName).build();
        return getPropertyDescriptor(specDescriptor);
    }

    private PropertyDescriptor getPropertyDescriptor(final PropertyDescriptor specDescriptor) {
        PropertyDescriptor descriptor = null;
        //check if property supported
        final List<PropertyDescriptor> supportedDescriptors = getSupportedPropertyDescriptors();
        if (supportedDescriptors != null) {
            for (final PropertyDescriptor desc : supportedDescriptors) { //find actual descriptor
                if (specDescriptor.equals(desc)) {
                    return desc;
                }
            }
        }

        descriptor = getSupportedDynamicPropertyDescriptor(specDescriptor.getName());
        if (descriptor != null && !descriptor.isDynamic()) {
            descriptor = new PropertyDescriptor.Builder().fromPropertyDescriptor(descriptor).dynamic(true).build();
        }

        if (descriptor == null) {
            descriptor = new PropertyDescriptor.Builder().fromPropertyDescriptor(specDescriptor).addValidator(Validator.INVALID).dynamic(true).build();
        }
        return descriptor;
    }

    @Override
    public final Collection<ValidationResult> validate(final ValidationContext context) {
        // goes through supported properties
        final Collection<ValidationResult> results = new ArrayList<>();
        final List<PropertyDescriptor> supportedDescriptors = getSupportedPropertyDescriptors();
        if (null != supportedDescriptors) {
            for (final PropertyDescriptor descriptor : supportedDescriptors) {
                String value = context.getProperty(descriptor).getValue();
                if (value == null) {
                    value = descriptor.getDefaultValue();
                }
                if (value == null && descriptor.isRequired()) {
                    results.add(new ValidationResult.Builder().valid(false).input(null).subject(descriptor.getName()).explanation(descriptor.getName() + " is required").build());
                    continue;
                } else if (value == null) {
                    continue;
                }

                final ValidationResult result = descriptor.validate(value, context);
                if (!result.isValid()) {
                    results.add(result);
                }
            }
        }

        // validate any dynamic properties
        for (final Map.Entry<PropertyDescriptor, String> entry : context.getProperties().entrySet()) {
            final PropertyDescriptor descriptor = entry.getKey();
            final String value = entry.getValue();

            if (supportedDescriptors != null && !supportedDescriptors.contains(descriptor)) {
                final ValidationResult result = descriptor.validate(value, context);
                if (!result.isValid()) {
                    results.add(result);
                }
            }
        }

        // only run customValidate if regular validation is successful. This allows Processor developers to not have to check
        // if values are null or invalid so that they can focus only on the interaction between the properties, etc.
        if (results.isEmpty()) {
            final Collection<ValidationResult> customResults = customValidate(context);
            if (null != customResults) {
                for (final ValidationResult result : customResults) {
                    if (!result.isValid()) {
                        results.add(result);
                    }
                }
            }
        }

        return results;
    }

    /**
     * Hook method allowing subclasses to eagerly react to a configuration
     * change for the given property descriptor. As an alternative to using this
     * method a processor may simply get the latest value whenever it needs it
     * and if necessary lazily evaluate it.
     *
     * @param descriptor
     * @param oldValue non-null property value (previous)
     * @param newValue the new property value or if null indicates the property
     * was removed
     */
    public void onPropertyModified(final PropertyDescriptor descriptor, final String oldValue, final String newValue) {
    }

    /**
     * <p>
     * Used to allow subclasses to determine what PropertyDescriptor if any to
     * use when a property is requested for which a descriptor is not already
     * registered. By default this method simply returns a null descriptor. By
     * overriding this method processor implementations can support dynamic
     * properties since this allows them to register properties on demand. It is
     * acceptable for a dynamically generated property to indicate it is
     * required so long as it is understood it is only required once set.
     * Dynamic properties by definition cannot be required until used.</p>
     *
     * <p>
     * This method should be side effect free in the subclasses in terms of how
     * often it is called for a given property name because there is guarantees
     * how often it will be called for a given property name.</p>
     *
     * <p>
     * Default is null.
     *
     * @param propertyDescriptorName
     * @return new property descriptor if supported
     */
    protected PropertyDescriptor getSupportedDynamicPropertyDescriptor(final String propertyDescriptorName) {
        return null;
    }

    /**
     * Allows subclasses to register which property descriptor objects are
     * supported. Default return is an empty set.
     *
     * @return PropertyDescriptor objects this processor currently supports
     */
    @SuppressWarnings("unchecked")
    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return Collections.EMPTY_LIST;
    }

    public final List<PropertyDescriptor> getPropertyDescriptors() {
        final List<PropertyDescriptor> descriptors = new ArrayList<>();
        descriptors.addAll(getSupportedPropertyDescriptors());
        return descriptors;
    }

    @Override
    public boolean equals(final Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (!(obj instanceof ConfigurableComponent)) {
            return false;
        }

        final ConfigurableComponent other = (ConfigurableComponent) obj;
        return getIdentifier().equals(other.getIdentifier());
    }

    @Override
    public int hashCode() {
        return 235 + getIdentifier().hashCode();
    }

    @Override
    public String toString() {
        return getClass().getSimpleName() + "[id=" + getIdentifier() + "]";
    }

}