/*
* 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.attribute.expression.language.evaluation.reduce;
import java.util.Map;
import org.apache.nifi.attribute.expression.language.evaluation.Evaluator;
import org.apache.nifi.attribute.expression.language.evaluation.QueryResult;
import org.apache.nifi.attribute.expression.language.evaluation.StringEvaluator;
import org.apache.nifi.attribute.expression.language.evaluation.StringQueryResult;
public class JoinEvaluator extends StringEvaluator implements ReduceEvaluator<String> {
private final Evaluator<String> subjectEvaluator;
private final Evaluator<String> delimiterEvaluator;
private final StringBuilder sb = new StringBuilder();
private int evalCount = 0;
public JoinEvaluator(final Evaluator<String> subject, final Evaluator<String> delimiter) {
this.subjectEvaluator = subject;
this.delimiterEvaluator = delimiter;
}
@Override
public QueryResult<String> evaluate(final Map<String, String> attributes) {
String subject = subjectEvaluator.evaluate(attributes).getValue();
if (subject == null) {
subject = "";
}
final String delimiter = delimiterEvaluator.evaluate(attributes).getValue();
if (evalCount > 0) {
sb.append(delimiter);
}
sb.append(subject);
evalCount++;
return new StringQueryResult(sb.toString());
}
@Override
public Evaluator<?> getSubjectEvaluator() {
return subjectEvaluator;
}
}