# SystemResolver.java

    /*
     * Copyright (c) 2018, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     * 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.
     */
    package org.apache.synapse.commons.resolvers;

    /**
     *  System resolver can be used to resolve environment variables in the synapse config.
     */
    public class SystemResolver implements Resolver {

        private String input;

        /**
         * set environment variable which needs to resolved
         **/
        @Override
        public void setVariable(String input) {
            this.input = input;
        }

        /**
         * environment variable is resolved in this function
         * @return resolved value for the environment variable
         */
        @Override
        public String resolve() {
            String envValue = System.getenv(input);
            if (envValue == null) {
                throw new ResolverException("Environment variable could not be found");
            }
            return envValue;
        }
    }