de.weltraumschaf.commons.ShutDownHook Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of commons Show documentation

Common Utility Classes for Java.

There is a newer version: 0.4.0

/*
 * LICENSE
 *
 * "THE BEER-WARE LICENSE" (Revision 43):
 * "Sven Strittmatter"  wrote this file.
 * As long as you retain this notice you can do whatever you want with
 * this stuff. If we meet some day, and you think this stuff is worth it,
 * you can buy me a non alcohol-free beer in return.
 *
 * Copyright (C) 2012 "Sven Strittmatter" 
 */
package de.weltraumschaf.commons;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Holds {@link Runnable callbacks} to execute them in any order.
 *
 * Example:
 * 
 * ShutDownHook hook = new ShutDownHook();
 * hook.register(new Runnable() {
 *
 *      @Override
 *      public void  run() {
 *          // Your shutdown code.
 *      }
 *
 * });
 * 
 * @author Sven Strittmatter 
 */
public class ShutDownHook extends Thread {

    /**
     * Default logger for this class.
     */
    private static final Logger DEFAULT_LOGGER = Logger.getLogger(ShutDownHook.class.getName());

    /**
     * Set of callbacks.
     */
    private final Set callbacks = new HashSet();

    /**
     * Logger instance.
     */
    private final Logger logger;

    /**
     * Initializes {@link #logger} with {@link #DEFAULT_LOGGER}.
     */
    public ShutDownHook() {
        this(DEFAULT_LOGGER);
    }

    /**
     * Designated constructor.
     *
     * @param logger Logger to use by this class.
     */
    public ShutDownHook(final Logger logger) {
        super();
        this.logger = logger;
    }

    /**
     * Iterates over all {@link #callbacks} and run them.
     */
    @Override
    public void run() {
        final Iterator iterator = callbacks.iterator();

        while (iterator.hasNext()) {
            try {
                iterator.next().run();
            } catch (Exception ex) {
                logger.log(Level.SEVERE, "Exception thrown by running a callback!", ex);
            }
        }
    }

    /**
     * Registers a callback.
     *
     * @param callback Runnable object.
     * @return Return itself for method chaining.
     */
    public ShutDownHook register(final Runnable callback) {
        callbacks.add(callback);
        return this;
    }

}