handlermap.java

一个工作流设计及定义的系统,可以直接与数据库结合进行系统工作流程的定义及应用.

/*
 * Copyright (c) 2005, John Mettraux, OpenWFE.org
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 * . Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.  
 * 
 * . Redistributions in binary form must reproduce the above copyright notice, 
 *   this list of conditions and the following disclaimer in the documentation 
 *   and/or other materials provided with the distribution.
 * 
 * . Neither the name of the "OpenWFE" nor the names of its contributors may be
 *   used to endorse or promote products derived from this software without
 *   specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * $Id: HandlerMap.java,v 1.15 2005/05/17 16:41:00 jmettraux Exp $
 */

//
// HandlerMap.java
//
// [e-mail]
//
// generated with 
// jtmpl 1.0.04 31.10.2002 John Mettraux ([e-mail])
//

package openwfe.org.uman.web;

import javax.servlet.ServletContext;
import openwfe.org.Parameters;
import openwfe.org.xml.XmlUtils;


/**
 * no comment
 *
 * <p><font size=2>CVS Info :
 * <br>$Author: jmettraux $
 * <br>$Date: 2005/05/17 16:41:00 $
 * <br>$Id: HandlerMap.java,v 1.15 2005/05/17 16:41:00 jmettraux Exp $ </font>
 *
 * @author [e-mail]
 */
public class HandlerMap
{

    private final static org.apache.log4j.Logger log = org.apache.log4j.Logger
        .getLogger(HandlerMap.class.getName());

    //
    // the singleton

    protected static HandlerMap theHandlerMap = null;

    //
    // CONSTANTS and definitions

    public final static String HANDLER_MAP_FILE_NAME
        = "handlerMapFileName";
    public final static String HANDLER
        = "handler";
    public final static String NAME
        = "name";
    public final static String CLASS
        = "class";
    public final static String HANDLES
        = "handles";
    public final static String FIELD
        = "field";

    //
    // FIELDS

    protected java.util.Map handlerMap = null;
    protected java.util.List handledList = null;

    //
    // CONSTRUCTORS

    public HandlerMap (ServletContext context)
        throws WumanException
    {
        String handlerMapFileName = 
            context.getInitParameter(HANDLER_MAP_FILE_NAME);

        handlerMapFileName = context.getRealPath(handlerMapFileName);

        if (handlerMapFileName == null)
        {
            throw new WumanException
                ("Parameter '"+HANDLER_MAP_FILE_NAME+
                 "' is mandatory in web.xml");
        }

        determineHandlers(handlerMapFileName);
    }

    //
    // METHODS

    public Handler getHandler (Class handledClass)
        throws WumanException
    {
        Object o = this.handlerMap.get(handledClass.getName());

        if (o == null)
        {
            throw new WumanException
                ("No handler defined for class '"+handledClass.getName()+"'");
        }

        if (o instanceof Handler)
        {
            return (Handler)o;
        }

        try
        {
            Class handlerClass = (Class)o;
            return (Handler)handlerClass.newInstance();
        }
        catch (Exception e)
        {
            throw new WumanException
                ("Failed to instantiate handler", e);
        }
    }

    /**
     * You could feed this method with 'java.security.Principal' and
     * it would return all the classes extending Principal and for
     * which there is a handler.
     * Returns a list of class names (String instances)
     */
    public java.util.List getHandledClasses (Class parentClass)
    {
        java.util.List result = 
            new java.util.ArrayList(this.handledList.size());

        java.util.Iterator it = this.handledList.iterator();
        while (it.hasNext())
        {
            Class c = (Class)it.next();

            /*
            log.debug
                ("is '"+parentClass.getName()+
                 "' assignable from '"+c.getName()+"'");
            */

            if (parentClass.isAssignableFrom(c)) 
            {
                //log.debug("TRUE");
                result.add(c.getName());
            }
        }

        java.util.Collections.sort(result);

        return result;
    }

    protected void determineHandlers (String handlerMapFileName)
        throws WumanException
    {
        this.handlerMap = new java.util.HashMap();
        this.handledList = new java.util.ArrayList();

        org.jdom.Element root = null;
        try
        {
            root = XmlUtils.extractXml(handlerMapFileName, false);
        }
        catch (Exception e)
        {
            throw new WumanException
                ("Failed to parse '"+handlerMapFileName+"'", e);
        }

        java.util.Iterator it = root.getChildren(HANDLER).iterator();
        while (it.hasNext())
        {
            org.jdom.Element eHandler = (org.jdom.Element)it.next();
            String handlerClassName = eHandler.getAttributeValue(CLASS);
            String handledClassName = eHandler.getAttributeValue(HANDLES);

            //
            // handlerMap

            Class handlerClass = null;
            try
            {
                handlerClass = Class.forName(handlerClassName);
            }
            catch (Exception e)
            {
                log.warn("Cannot load handlerClass. Skipped it.", e);
                continue;
            }
        
            log.debug
                ("Adding mapping '"+handledClassName+
                 "' -> '"+handlerClassName+"'");

            this.handlerMap.put(handledClassName, handlerClass);

            //
            // handledList

            Class handledClass = null;
            try
            {
                handledClass = Class.forName(handledClassName);
            }
            catch (Exception e)
            {
                log.warn("Cannot load handledClass. Skipped it.", e);
                continue;
            }
            //log.debug("Adding handled class '"+handledClassName+"'");
            this.handledList.add(handledClass);

            //
            // fields (for DynamicHandler)

            if (DynamicHandler.class.isAssignableFrom(handlerClass))
            {
                DynamicHandler dynamicHandler = null;
                try
                {
                    dynamicHandler = (DynamicHandler)handlerClass.newInstance();
                    dynamicHandler.setHandledClass(handledClass);
                }
                catch (Exception e)
                {
                    log.warn("Failed to instantiate dynamic handler", e);
                    continue;
                }

                java.util.Iterator fit = eHandler.getChildren(FIELD).iterator();
                while (fit.hasNext())
                {
                    dynamicHandler.addField
                        (buildField((org.jdom.Element)fit.next()));
                }
                this.handlerMap.put(handledClassName, dynamicHandler);
            }
        }
    }

    protected Field buildField (org.jdom.Element eField)
        throws WumanException
    {
        String name = eField.getAttributeValue(NAME);
        String className = eField.getAttributeValue(CLASS);

        if (name == null || className == null)
        {
            throw new WumanException
                ("attribute '"+NAME+
                 "' or '"+CLASS+
                 "' is missing from element '"+FIELD+"'");
        }

        try
        {
            java.util.Map initParams = 
                Parameters.extractParameters(eField);

            return 
                Field.buildField(name, className, initParams);
        }
        catch (Exception e)
        {
            throw new WumanException
                ("Failed to build field", e);
        }
    }

    //
    // STATIC METHODS

    public static HandlerMap getHandlerMap 
        (ServletContext context)
    throws 
        WumanException
    {
        if (theHandlerMap != null) return theHandlerMap;

        synchronized (HandlerMap.class)
        {
            theHandlerMap = new HandlerMap(context);
            return theHandlerMap;
        }
    }

}