webhcat/svr/src/main/java/org/apache/hcatalog/templeton/tool/TrivialExecService.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.hcatalog.templeton.tool;

import java.io.IOException;
import java.util.List;
import java.util.Map;

/**
 * Execute a local program.  This is a singleton service that will
 * execute a programs on the local box.
 */
public class TrivialExecService {
    private static volatile TrivialExecService theSingleton;

    /**
     * Retrieve the singleton.
     */
    public static synchronized TrivialExecService getInstance() {
        if (theSingleton == null)
            theSingleton = new TrivialExecService();
        return theSingleton;
    }

    public Process run(List<String> cmd, List<String> removeEnv,
                       Map<String, String> environmentVariables)
        throws IOException {
        System.err.println("templeton: starting " + cmd);
        System.err.print("With environment variables: ");
        for (Map.Entry<String, String> keyVal : environmentVariables.entrySet()) {
            System.err.println(keyVal.getKey() + "=" + keyVal.getValue());
        }
        ProcessBuilder pb = new ProcessBuilder(cmd);
        for (String key : removeEnv)
            pb.environment().remove(key);
        pb.environment().putAll(environmentVariables);
        return pb.start();
    }

}