Groovy example source code file (ListenerList.groovy)

This example Groovy source code file (ListenerList.groovy) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

annotation, listenerlist, listenerlist, string, string

The Groovy ListenerList.groovy source code

/*
 * Copyright 2003-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package groovy.beans

import java.lang.annotation.ElementType
import java.lang.annotation.Retention
import java.lang.annotation.RetentionPolicy
import java.lang.annotation.Target
import org.codehaus.groovy.transform.GroovyASTTransformationClass


/**
 * This annotation adds Java-style listener support to a class based on an annotated Collection-property. <br/>

 *
 * For any given Collection property, several methods will be written into the enclosing class during the compile phase. These
 * changes are visible from Java or other languages. The List is intended to hold listeners of some sort, and the methods
 * addListener, removeListener, and getListeners are all added to the class. The actual methods names depend on the generic
 * type of the collection.
 *
 * Given the following example:<br/>
 * <pre>
 * class MyClass {
 *     @groovy.beans.ListenerList
 *     List<java.awt.event.ActionListener> listeners
 * }
 * </pre>
 * The following code is generated:
 * <pre>
 * public class MyClass extends java.lang.Object {
 *
 *     @groovy.beans.ListenerList
 *     private java.util.List<java.awt.event.ActionListener> listeners
 *
 *     public void addActionListener(java.awt.event.ActionListener listener) {
 *         if ( listener == null) {
 *             return null
 *         }
 *         if ( listeners == null) {
 *             listeners = []
 *         }
 *         listeners.add(listener)
 *     }
 *
 *     public void removeActionListener(java.awt.event.ActionListener listener) {
 *         if ( listener == null) {
 *             return null
 *         }
 *         if ( listeners == null) {
 *             listeners = []
 *         }
 *         listeners.remove(listener)
 *     }
 *
 *     public java.awt.event.ActionListener[] getActionListeners() {
 *         java.lang.Object __result = []
 *         if ( listeners != null) {
 *             __result.addAll(listeners)
 *         }
 *         return (( __result ) as java.awt.event.ActionListener[])
 *     }
 *
 *     public void fireActionPerformed(java.awt.event.ActionEvent param0) {
 *         if ( listeners != null) {
 *             def __list = new java.util.ArrayList(listeners)
 *             for (java.lang.Object listener : __list ) {
 *                 listener.actionPerformed(param0)
 *             }
 *         }
 *     }
 * }
 * </pre>
 * A fire method is created for each public method in the target class. In this case, ActionListener only has one
 * method. For a four method interface, four fire methods would be created. <br/>

 * 
 * The annotation can take the following parameters:
 * <pre>
 * name        = a suffix for creating the add, remove, and get methods.
 *               Default: Name of the listener type
 *               In the above example, if name is set to MyListener, then the class will have an addMyListener,
 *               removeMyListener, and getMyListeners methods. 
 *
 * synchronize = Whether or not the methods created should be synchronized at the method level. 
 *               Default: false
 * </pre>
 *
 * <strong>Compilation Errors - Using this annotation incorrectly results in compilation errors rather
 * than runtime errors. A list of potential problems includes:
 * <ul>
 * <li>This annotation can only be applied to a field of type Collection
 * <li>The annotated Collection field must have a generic type
 * <li>The annotated Collection field must not have a generic wildcard declared
 * <li>The generated methods must not already exist
 * </ul>
 * @see ListenerListASTTransformation
 *
 * @author Alexander Klein
 * @author Hamlet D'Arcy
 */
@java.lang.annotation.Documented
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.FIELD)
@GroovyASTTransformationClass('groovy.beans.ListenerListASTTransformation')
@interface ListenerList {
    String name() default ""
    boolean synchronize() default false
}