IsNullEvaluator.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.hl7.query.evaluator.comparison;

import java.util.Collection;
import java.util.Map;

import org.apache.nifi.hl7.model.HL7Component;
import org.apache.nifi.hl7.query.evaluator.BooleanEvaluator;
import org.apache.nifi.hl7.query.evaluator.Evaluator;

public class IsNullEvaluator extends BooleanEvaluator {

    private final Evaluator<?> subjectEvaluator;

    public IsNullEvaluator(final Evaluator<?> subjectEvaluator) {
        this.subjectEvaluator = subjectEvaluator;
    }

    @Override
    public Boolean evaluate(final Map<String, Object> objectMap) {
        Object subjectValue = subjectEvaluator.evaluate(objectMap);
        if (subjectValue == null) {
            return true;
        }

        return isNull(subjectValue);
    }

    private boolean isNull(Object subjectValue) {
        if (subjectValue == null) {
            return true;
        }

        if (subjectValue instanceof HL7Component) {
            subjectValue = ((HL7Component) subjectValue).getValue();
        }

        if (subjectValue instanceof Collection) {
            final Collection<?> collection = (Collection<?>) subjectValue;
            if (collection.isEmpty()) {
                return true;
            }

            for (final Object obj : collection) {
                if (!isNull(obj)) {
                    return false;
                }
            }

            return true;
        }

        return subjectValue == null;
    }
}