components/camel-spark-rest/src/main/java/org/apache/camel/component/sparkrest/SparkHelper.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.camel.component.sparkrest;

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

public final class SparkHelper {

    private SparkHelper() {
    }

    /**
     * Appends the key/value to the headers.
     * <p/>
     * This implementation supports keys with multiple values. In such situations the value
     * will be a {@link java.util.List} that contains the multiple values.
     *
     * @param headers  headers
     * @param key      the key
     * @param value    the value
     */
    @SuppressWarnings("unchecked")
    public static void appendHeader(Map<String, Object> headers, String key, Object value) {
        if (headers.containsKey(key)) {
            Object existing = headers.get(key);
            List<Object> list;
            if (existing instanceof List) {
                list = (List<Object>) existing;
            } else {
                list = new ArrayList<>();
                list.add(existing);
            }
            list.add(value);
            value = list;
        }

        headers.put(key, value);
    }

}