vm/vmcore/src/kernel_classes/javasrc/java/lang/VMStart.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.
 */
/*
 * @author Artem Aliev
 */

package java.lang;

import java.util.Properties;
import java.util.Enumeration;


/**
 * This class does the following:
 * <li> starts Finalizer and Execution Manager helper threads.
 * <li> parses system properties and configure VM environment.
 * </ul> 
 */
class VMStart {

    public static void initialize() {
        //start helper threads such as Finalizer
        startHelperThreads();
        // add default shutdown hooks, to stop helper threads.
        Runtime.getRuntime().addShutdownHook(new DefaultShutDownHook());
        // do additional tasks specified in system properties       
        parseSystemProperties();
    }

    /** 
        Any component can ask VMStart to initialize it's class
        using  vm.component.<component name>.startupclass property
    */
    private static final String STARTUP_CLASS_PREFIX="vm.components.";
    private static final String STARTUP_CLASS_SUFFUX=".startupclass";

    public static void parseSystemProperties() {
        //call class.forName for all startup classes 
        Properties p = System.getProperties();
        for (Enumeration it=p.propertyNames(); it.hasMoreElements();) {
            String key = (String)it.nextElement();
            if (key.startsWith(STARTUP_CLASS_PREFIX) && key.endsWith(STARTUP_CLASS_SUFFUX)) {
                String className = p.getProperty(key);
                try {
                    Class.forName(className);
                } catch (Exception e) {
                    e.printStackTrace();
                    //TODO: should be call System.exit() here?
                }

            }
        }
        
    }
    
    public static void startHelperThreads() {
        try {
            // start helper threads.
            FinalizerThread.initialize();
            EMThreadSupport.initialize();
        } catch (Throwable e) {
            System.err.println("Internal error");
            e.printStackTrace(System.err);
            Runtime.getRuntime().halt(1);
        }
    }
    // should shutdown helper threads
    static class DefaultShutDownHook extends Thread {
        
        public DefaultShutDownHook() {
            super("Thread-shutdown");
        }

        public void run() {
            EMThreadSupport.shutdown();
        }
    }
}