classutil.java

wiki建站资源 java编写的 很好用

/* 
    JSPWiki - a JSP-based WikiWiki clone.

    Copyright (C) 2001-2003 Janne Jalkanen ([e-mail])

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser 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 com.ecyrd.jspwiki.util;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 *  Contains useful utilities for class file manipulation.
 *
 *  @author Janne Jalkanen
 *  @since 2.1.29.
 */
public class ClassUtil
{
    /**
     *  Attempts to find a class from a collection of packages.  This will first
     *  attempt to find the class based on just the className parameter, but
     *  should that fail, will iterate through the "packages" -list, prefixes
     *  the package name to the className, and then tries to find the class
     *  again.
     *
     *  @param packages A List of Strings, containing different package names.
     *  @param className The name of the class to find.
     *  @return The class, if it was found.
     *  @throws ClassNotFoundException if this particular class cannot be found
     *          from the list.
     */
    public static Class findClass( List packages, String className )
        throws ClassNotFoundException
    {
        ClassLoader loader = ClassUtil.class.getClassLoader();

        try
        {
            return loader.loadClass( className );
        }
        catch( ClassNotFoundException e )
        {
            for( Iterator i = packages.iterator(); i.hasNext(); )
            {
                String packageName = (String)i.next();

                try
                {
                    return loader.loadClass( packageName + "." + className );
                }
                catch( ClassNotFoundException ex )
                {
                    // This is okay, we go to the next package.
                }
            }
        }

        throw new ClassNotFoundException("Class not found in search path!");
    }
    
    /**
     *  A shortcut for findClass when you only have a singular package to search.
     *  It will first attempt to instantiate the class directly from the className,
     *  and will then try to prefix it with the packageName.
     *
     *  @param packageName A package name (such as "com.ecyrd.jspwiki.plugins").
     *  @param className The class name to find.
     *  @return The class, if it was found.
     *  @throws ClassNotFoundException if this particular class cannot be found.
     */

    public static Class findClass( String packageName, String className )
        throws ClassNotFoundException
    {
        ArrayList list = new ArrayList();
        list.add( packageName );

        return findClass( list, className );
    }
}