be.Balor.Tools.Compatibility.CachedPackage.java Source code

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Here is the source code for be.Balor.Tools.Compatibility.CachedPackage.java

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/*
 *  ProtocolLib - Bukkit server library that allows access to the Minecraft protocol.
 *  Copyright (C) 2012 Kristian S. Stangeland
 *
 *  This program is free software; you can redistribute it and/or modify it under the terms of the 
 *  GNU General Public License as published by the Free Software Foundation; either version 2 of 
 *  the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; 
 *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 *  See the GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along with this program; 
 *  if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 
 *  02111-1307 USA
 */

package be.Balor.Tools.Compatibility;

import java.util.Map;

import com.google.common.collect.Maps;

/**
 * Represents a dynamic package and an arbitrary number of cached classes.
 * 
 * @author Kristian
 */
class CachedPackage {
    private final Map<String, Class<?>> cache;
    private final String packageName;

    public CachedPackage(final String packageName) {
        this.packageName = packageName;
        this.cache = Maps.newConcurrentMap();
    }

    /**
     * Associate a given class with a class name.
     * 
     * @param className
     *            - class name.
     * @param clazz
     *            - type of class.
     */
    public void setPackageClass(final String className, final Class<?> clazz) {
        cache.put(className, clazz);
    }

    /**
     * Retrieve the class object of a specific class in the current package.
     * 
     * @param className
     *            - the specific class.
     * @return Class object.
     * @throws RuntimeException
     *             If we are unable to find the given class.
     */
    public Class<?> getPackageClass(final String className) {
        try {
            Class<?> result = cache.get(className);

            // Concurrency is not a problem - we don't care if we look up a
            // class twice
            if (result == null) {
                // Look up the class dynamically
                result = CachedPackage.class.getClassLoader().loadClass(combine(packageName, className));
                cache.put(className, result);
            }

            return result;

        } catch (final ClassNotFoundException e) {
            throw new RuntimeException("Cannot find class " + className, e);
        }
    }

    /**
     * Correctly combine a package name and the child class we're looking for.
     * 
     * @param packageName
     *            - name of the package, or an empty string for the default
     *            package.
     * @param className
     *            - the class name.
     * @return We full class path.
     */
    private String combine(final String packageName, final String className) {
        if (packageName.length() == 0) {
            return className;
        }
        return packageName + "." + className;
    }
}