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Camel Properties component

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/*
 * 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.properties;

import java.util.Locale;

import org.apache.camel.util.StringHelper;

/**
 * A {@link org.apache.camel.component.properties.PropertiesFunction} that lookup the property value from
 * OS environment variables using the service idiom.
 * 
 * A service is defined using two environment variables where name is name of the service:
 * 

 *   NAME_SERVICE_HOST
 *   NAME_SERVICE_PORT
 * 
 * in other words the service uses _SERVICE_HOST and _SERVICE_PORT as prefix.
 * 
 * This implementation is to return the port part only.
 *
 * @see ServicePropertiesFunction
 * @see ServiceHostPropertiesFunction
 */
public class ServicePortPropertiesFunction implements PropertiesFunction {

    private static final String PORT_PREFIX = "_SERVICE_PORT";

    @Override
    public String getName() {
        return "service.port";
    }

    @Override
    public String apply(String remainder) {
        String key = remainder;
        String defaultValue = null;

        if (remainder.contains(":")) {
            key = StringHelper.before(remainder, ":");
            defaultValue = StringHelper.after(remainder, ":");
        }

        // make sure to use upper case
        if (key != null) {
            // make sure to use underscore as dash is not supported as ENV variables
            key = key.toUpperCase(Locale.ENGLISH).replace('-', '_');

            // a service should have both the host and port defined
            String port = System.getenv(key + PORT_PREFIX);

            if (port != null) {
                return port;
            } else {
                return defaultValue;
            }
        }

        return defaultValue;
    }
}