AttributeComparator.java

package org.dynamoframework.domain.comparator;

/*-
 * #%L
 * Dynamo Framework
 * %%
 * Copyright (C) 2014 - 2024 Open Circle Solutions
 * %%
 * Licensed 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.
 * #L%
 */

import lombok.AllArgsConstructor;
import lombok.Getter;
import org.dynamoframework.domain.AbstractEntity;
import org.dynamoframework.utils.ClassUtils;

import java.util.Comparator;

/**
 * A comparator for comparing two entities based on a value of an attribute (using reflection)
 *
 * @author bas.rutten
 */
@Getter
@AllArgsConstructor
public class AttributeComparator<T extends AbstractEntity<?>> implements Comparator<T> {

	private final String attribute;

	@Override
	@SuppressWarnings({"unchecked"})
	public int compare(T o1, T o2) {
		Object v1 = ClassUtils.getFieldValue(o1, attribute);
		Object v2 = ClassUtils.getFieldValue(o2, attribute);

		if (v1 == null && v2 == null) {
			return 0;
		} else if (v1 == null) {
			return -1;
		} else if (v2 == null) {
			return 1;
		} else if (v1 instanceof String str1) {
			return str1.compareToIgnoreCase((String) v2);
		} else if (v1 instanceof Comparable comp) {
			return comp.compareTo(v2);
		}
		return 0;
	}
}