java.com.generationjava.lang.Notifier Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of gj-core Show documentation
A re-usable library of Java classes. Originally stand-alone, many of the classes have since gone into various parts of the Jakarta Commons project, and thus this package contains various dependencies.
The newest version!
/*
 * Copyright (c) 2003, Henri Yandell
 * 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 Genjava-Core 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.
 */
package com.generationjava.lang;

import java.util.ArrayList;
import java.util.EventObject;
import java.util.Iterator;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

public class Notifier {

    private ArrayList listeners = new ArrayList();
    private Method listenerMethod;
    private String methodName;
    private Class clss;

    public Notifier(Class listener) {
        if(listener == null) {
            throw new IllegalArgumentException("Illegal to have a null listener Class. ");
        }
        
        this.clss = listener;
        // now we check methods, if only one of them, then 
        // let's set it
        Method[] meths = clss.getDeclaredMethods();
        if(meths.length == 0) {
            this.listenerMethod = meths[0];
        }
    }

    /**
     * Construct with the class and the name of the method to
     * call upon the listeners.
     */
    public Notifier(Class clss, String name) {
        if(clss == null) {
            throw new IllegalArgumentException("Illegal to have a null Listener Class. ");
        }
        if(name == null) {
            throw new IllegalArgumentException("Illegal to have a null method name. ");
        }
        this.clss = clss;
        this.methodName = name;
        try {
            // then we get the Method object
            this.listenerMethod = this.clss.getDeclaredMethod(name, new Class[] { EventObject.class} );
        } catch(NoSuchMethodException nsme) {
            throw new IllegalArgumentException("Method not on Class. ");
        }
    }

    public void addListener(Object not) {
        this.listeners.add(not);
    }

    public void removeListener(Object not) {
        this.listeners.remove(not);
    }

    public ArrayList getListeners() {
        ArrayList cloned = new ArrayList();
        cloned.addAll(listeners);
        return cloned;
    }


    /**
     * Convenience method for when a listener has a single method.
     *
     * Currently this method needs to be called, but it's possible
     * that by providing the interface class, it can be assumed as 
     * to what the listening method is.
     */
    public void notify(EventObject event) throws NotifierException {
        if(this.clss == null) {
            notify(this.methodName, event);
        } else {
            notify(this.listenerMethod, event);
        }
    }

    /**
     * Notify the listeners of a certain event, to a certain method.
     *
     * This is usable when a Listener has more than one method and
     * a single Notifier wants to be shared.
     */
    private void notify(Method listenerMethod, EventObject event) throws NotifierException {
        Iterator itr = getListeners().iterator();
        while(itr.hasNext()) {
            try {
                Object listener = itr.next();
                listenerMethod.invoke( listener, new Object[] { event } );
            } catch(SecurityException se) {
                throw new NotifierException(se);
            } catch(IllegalAccessException iae) {
                throw new NotifierException(iae);
            } catch(IllegalArgumentException iae) {
                throw new NotifierException(iae);
            } catch(InvocationTargetException ite) {
                throw new NotifierException(ite);
            }
        }
    }

    /**
     * Notify the listeners of a certain event, to a certain method.
     *
     * This is usable when a Listener has more than one method and
     * a single Notifier wants to be shared.
     */
    public void notify(String methodName, EventObject event) throws NotifierException {
        Iterator itr = getListeners().iterator();
        while(itr.hasNext()) {
            try {
                Object listener = itr.next();
                Class clss = listener.getClass();
                Method method = clss.getMethod(methodName, new Class[] { event.getClass() } );
                method.invoke( listener, new Object[] { event } );
            } catch(SecurityException se) {
                throw new NotifierException(se);
            } catch(NoSuchMethodException nsme) {
                throw new NotifierException(nsme);
            } catch(IllegalAccessException iae) {
                throw new NotifierException(iae);
            } catch(IllegalArgumentException iae) {
                throw new NotifierException(iae);
            } catch(InvocationTargetException ite) {
                throw new NotifierException(ite);
            }
        }
    }

}