| Frames | No Frames |
1: /* java.beans.EventHandler 2: Copyright (C) 2004, 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package java.beans; 40: 41: import java.lang.reflect.InvocationHandler; 42: import java.lang.reflect.InvocationTargetException; 43: import java.lang.reflect.Method; 44: import java.lang.reflect.Proxy; 45: 46: /** 47: * <p>EventHandler forms a bridge between dynamically created listeners and 48: * arbitrary properties and methods.</p> 49: * 50: * <p>You can use this class to easily create listener implementations for 51: * some basic interactions between an event source and its target. Using 52: * the three static methods named <code>create</code> you can create 53: * these listener implementations.</p> 54: * 55: * <p>See the documentation of each method for usage examples.</p> 56: * 57: * @author Jerry Quinn (jlquinn@optonline.net) 58: * @author Robert Schuster (thebohemian@gmx.net) 59: * @since 1.4 60: */ 61: public class EventHandler implements InvocationHandler 62: { 63: // The name of the method that will be implemented. If null, any method. 64: private String listenerMethod; 65: 66: // The object to call action on. 67: private Object target; 68: 69: // The name of the method or property setter in target. 70: private String action; 71: 72: // The property to extract from an event passed to listenerMethod. 73: private String property; 74: 75: // The target objects Class. 76: private Class targetClass; 77: 78: // String class doesn't already have a capitalize routine. 79: private String capitalize(String s) 80: { 81: return s.substring(0, 1).toUpperCase() + s.substring(1); 82: } 83: 84: /** 85: * Creates a new <code>EventHandler</code> instance. 86: * 87: * <p>Typical creation is done with the create method, not by knewing an 88: * EventHandler.</p> 89: * 90: * <p>This constructs an EventHandler that will connect the method 91: * listenerMethodName to target.action, extracting eventPropertyName from 92: * the first argument of listenerMethodName. and sending it to action.</p> 93: * 94: * <p>Throws a <code>NullPointerException</code> if the <code>target</code> 95: * argument is <code>null</code>. 96: * 97: * @param target Object that will perform the action. 98: * @param action A property or method of the target. 99: * @param eventPropertyName A readable property of the inbound event. 100: * @param listenerMethodName The listener method name triggering the action. 101: */ 102: public EventHandler(Object target, String action, String eventPropertyName, 103: String listenerMethodName) 104: { 105: this.target = target; 106: 107: // Retrieving the class is done for two reasons: 108: // 1) The class object is needed very frequently in the invoke() method. 109: // 2) The constructor should throw a NullPointerException if target is null. 110: targetClass = target.getClass(); 111: 112: this.action = action; // Turn this into a method or do we wait till 113: // runtime 114: property = eventPropertyName; 115: listenerMethod = listenerMethodName; 116: } 117: 118: /** 119: * Returns the event property name. 120: */ 121: public String getEventPropertyName() 122: { 123: return property; 124: } 125: 126: /** 127: * Returns the listener's method name. 128: */ 129: public String getListenerMethodName() 130: { 131: return listenerMethod; 132: } 133: 134: /** 135: * Returns the target object. 136: */ 137: public Object getTarget() 138: { 139: return target; 140: } 141: 142: /** 143: * Returns the action method name. 144: */ 145: public String getAction() 146: { 147: return action; 148: } 149: 150: // Fetch a qualified property like a.b.c from object o. The properties can 151: // be boolean isProp or object getProp properties. 152: // 153: // Returns a length 2 array with the first entry containing the value 154: // extracted from the property, and the second entry contains the class of 155: // the method return type. 156: // 157: // We play this game because if the method returns a native type, the return 158: // value will be a wrapper. If we then take the type of the wrapper and use 159: // it to locate the action method that takes the native type, it won't match. 160: private Object[] getProperty(Object o, String prop) 161: { 162: // Isolate the first property name from a.b.c. 163: int pos; 164: String rest = null; 165: if ((pos = prop.indexOf('.')) != -1) 166: { 167: rest = prop.substring(pos + 1); 168: prop = prop.substring(0, pos); 169: } 170: 171: // Find a method named getProp. It could be isProp instead. 172: Method getter; 173: try 174: { 175: // Look for boolean property getter isProperty 176: getter = o.getClass().getMethod("is" + capitalize(prop)); 177: } 178: catch (NoSuchMethodException nsme1) 179: { 180: try { 181: // Look for regular property getter getProperty 182: getter = o.getClass().getMethod("get" + capitalize(prop)); 183: } catch(NoSuchMethodException nsme2) { 184: try { 185: // Finally look for a method of the name prop 186: getter = o.getClass().getMethod(prop); 187: } catch(NoSuchMethodException nsme3) { 188: // Ok, give up with an intelligent hint for the user. 189: throw new RuntimeException("Method not called: Could not find a property or method '" + prop 190: + "' in " + o.getClass() + " while following the property argument '" + property + "'."); 191: } 192: } 193: } 194: try { 195: Object val = getter.invoke(o); 196: 197: if (rest != null) 198: return getProperty(val, rest); 199: 200: return new Object[] {val, getter.getReturnType()}; 201: } catch(InvocationTargetException ite) { 202: throw new RuntimeException("Method not called: Property or method '" + prop + "' has thrown an exception.", ite); 203: } catch(IllegalAccessException iae) { 204: // This cannot happen because we looked up method with Class.getMethod() 205: // which returns public methods only. 206: throw (InternalError) new InternalError("Non-public method was invoked.").initCause(iae); 207: } 208: } 209: 210: /** 211: * Invokes the <code>EventHandler</code>. 212: * 213: * <p>This method is normally called by the listener's proxy implementation.</p> 214: * 215: * @param proxy The listener interface that is implemented using 216: * the proxy mechanism. 217: * @param method The method that was called on the proxy instance. 218: * @param arguments The arguments which where given to the method. 219: * @throws Throwable <code>NoSuchMethodException</code> is thrown when the EventHandler's 220: * action method or property cannot be found. 221: */ 222: public Object invoke(Object proxy, Method method, Object[] arguments) 223: { 224: try { 225: // The method instance of the target object. We have to find out which 226: // one we have to invoke. 227: Method actionMethod = null; 228: 229: // Listener methods that weren't specified are ignored. If listenerMethod 230: // is null, then all listener methods are processed. 231: if (listenerMethod != null && !method.getName().equals(listenerMethod)) 232: return null; 233: 234: // If a property is defined we definitely need a valid object at 235: // arguments[0] that can be used to retrieve a value to which the 236: // property of the target gets set. 237: if(property != null) { 238: // Extracts the argument. We will let it fail with a NullPointerException 239: // the caller used a listener method that has no arguments. 240: Object event = arguments[0]; 241: 242: // Obtains the property XXX propertyType keeps showing up null - why? 243: // because the object inside getProperty changes, but the ref variable 244: // can't change this way, dolt! need a better way to get both values out 245: // - need method and object to do the invoke and get return type 246: Object v[] = getProperty(event, property); 247: Object[] args = new Object[] { v[0] }; 248: 249: // Changes the class array that controls which method signature we are going 250: // to look up in the target object. 251: Class[] argTypes = new Class[] { initClass((Class) v[1]) }; 252: 253: // Tries to find a setter method to which we can apply the 254: while(argTypes[0] != null) { 255: try 256: { 257: // Look for a property setter for action. 258: actionMethod = targetClass.getMethod("set" + capitalize(action), argTypes); 259: 260: return actionMethod.invoke(target, args); 261: } 262: catch (NoSuchMethodException e) 263: { 264: // If action as property didn't work, try as method later. 265: } 266: 267: argTypes[0] = nextClass(argTypes[0]); 268: } 269: 270: // We could not find a suitable setter method. Now we try again interpreting 271: // action as the method name itself. 272: // Since we probably have changed the block local argTypes array 273: // we need to rebuild it. 274: argTypes = new Class[] { initClass((Class) v[1]) }; 275: 276: // Tries to find a setter method to which we can apply the 277: while(argTypes[0] != null) { 278: try 279: { 280: actionMethod = targetClass.getMethod(action, argTypes); 281: 282: return actionMethod.invoke(target, args); 283: } 284: catch (NoSuchMethodException e) 285: { 286: } 287: 288: argTypes[0] = nextClass(argTypes[0]); 289: } 290: 291: throw new RuntimeException("Method not called: Could not find a public method named '" 292: + action + "' in target " + targetClass + " which takes a '" 293: + v[1] + "' argument or a property of this type."); 294: } 295: 296: // If property was null we will search for a no-argument method here. 297: // Note: The ordering of method lookups is important because we want to prefer no-argument 298: // calls like the JDK does. This means if we have actionMethod() and actionMethod(Event) we will 299: // call the first *EVEN* if we have a valid argument for the second method. This is behavior compliant 300: // to the JDK. 301: // If actionMethod() is not available but there is a actionMethod(Event) we take this. That makes us 302: // more specification compliant than the JDK itself because this one will fail in such a case. 303: try 304: { 305: actionMethod = targetClass.getMethod(action); 306: } 307: catch(NoSuchMethodException nsme) 308: { 309: // Note: If we want to be really strict the specification says that a no-argument method should 310: // accept an EventObject (or subclass I guess). However since the official implementation is broken 311: // anyways, it's more flexible without the EventObject restriction and we are compatible on everything 312: // else this can stay this way. 313: if(arguments != null && arguments.length >= 1/* && arguments[0] instanceof EventObject*/) { 314: Class[] targetArgTypes = new Class[] { initClass(arguments[0].getClass()) }; 315: 316: while(targetArgTypes[0] != null) { 317: try 318: { 319: // If no property exists we expect the first element of the arguments to be 320: // an EventObject which is then applied to the target method. 321: 322: actionMethod = targetClass.getMethod(action, targetArgTypes); 323: 324: return actionMethod.invoke(target, new Object[] { arguments[0] }); 325: } 326: catch(NoSuchMethodException nsme2) 327: { 328: 329: } 330: 331: targetArgTypes[0] = nextClass(targetArgTypes[0]); 332: } 333: 334: } 335: } 336: 337: // If we do not have a Method instance at this point this means that all our tries 338: // failed. The JDK throws an ArrayIndexOutOfBoundsException in this case. 339: if(actionMethod == null) 340: throw new ArrayIndexOutOfBoundsException(0); 341: 342: // Invoke target.action(property) 343: return actionMethod.invoke(target); 344: } catch(InvocationTargetException ite) { 345: throw new RuntimeException(ite.getCause()); 346: } catch(IllegalAccessException iae) { 347: // Cannot happen because we always use getMethod() which returns public 348: // methods only. Otherwise there is something seriously broken in 349: // GNU Classpath. 350: throw (InternalError) new InternalError("Non-public method was invoked.").initCause(iae); 351: } 352: } 353: 354: /** 355: * <p>Returns the primitive type for every wrapper class or the 356: * class itself if it is no wrapper class.</p> 357: * 358: * <p>This is needed because to be able to find both kinds of methods: 359: * One that takes a wrapper class as the first argument and one that 360: * accepts a primitive instead.</p> 361: */ 362: private Class initClass(Class klass) { 363: if(klass == Boolean.class) { 364: return Boolean.TYPE; 365: } else if(klass == Byte.class) { 366: return Byte.TYPE; 367: } else if(klass == Short.class) { 368: return Short.TYPE; 369: } else if(klass == Integer.class) { 370: return Integer.TYPE; 371: } else if(klass == Long.class) { 372: return Long.TYPE; 373: } else if(klass == Float.class) { 374: return Float.TYPE; 375: } else if(klass == Double.class) { 376: return Double.TYPE; 377: } else { 378: return klass; 379: } 380: } 381: 382: /** 383: * 384: * 385: * @param klass 386: * @return 387: */ 388: private Class nextClass(Class klass) { 389: if(klass == Boolean.TYPE) { 390: return Boolean.class; 391: } else if(klass == Byte.TYPE) { 392: return Byte.class; 393: } else if(klass == Short.TYPE) { 394: return Short.class; 395: } else if(klass == Integer.TYPE) { 396: return Integer.class; 397: } else if(klass == Long.TYPE) { 398: return Long.class; 399: } else if(klass == Float.TYPE) { 400: return Float.class; 401: } else if(klass == Double.TYPE) { 402: return Double.class; 403: } else { 404: return klass.getSuperclass(); 405: } 406: } 407: 408: /** 409: * <p>Constructs an implementation of <code>listenerInterface</code> 410: * to dispatch events.</p> 411: * 412: * <p>You can use such an implementation to simply call a public 413: * no-argument method of an arbitrary target object or to forward 414: * the first argument of the listener method to the target method.</p> 415: * 416: * <p>Call this method like:</p> 417: * <code> 418: * button.addActionListener((ActionListener) 419: * EventHandler.create(ActionListener.class, target, "dispose")); 420: * </code> 421: * 422: * <p>to achieve the following behavior:</p> 423: * <code> 424: * button.addActionListener(new ActionListener() { 425: * public void actionPerformed(ActionEvent ae) { 426: * target.dispose(); 427: * } 428: * }); 429: * </code> 430: * 431: * <p>That means if you need a listener implementation that simply calls a 432: * a no-argument method on a given instance for <strong>each</strong> 433: * method of the listener interface.</p> 434: * 435: * <p>Note: The <code>action</code> is interpreted as a method name. If your target object 436: * has no no-argument method of the given name the EventHandler tries to find 437: * a method with the same name but which can accept the first argument of the 438: * listener method. Usually this will be an event object but any other object 439: * will be forwarded, too. Keep in mind that using a property name instead of a 440: * real method here is wrong and will throw an <code>ArrayIndexOutOfBoundsException</code> 441: * whenever one of the listener methods is called.<p/> 442: * 443: * <p>The <code>EventHandler</code> will automatically convert primitives 444: * to their wrapper class and vice versa. Furthermore it will call 445: * a target method if it accepts a superclass of the type of the 446: * first argument of the listener method.</p> 447: * 448: * <p>In case that the method of the target object throws an exception 449: * it will be wrapped in a <code>RuntimeException</code> and thrown out 450: * of the listener method.</p> 451: * 452: * <p>In case that the method of the target object cannot be found an 453: * <code>ArrayIndexOutOfBoundsException</code> will be thrown when the 454: * listener method is invoked.</p> 455: * 456: * <p>A call to this method is equivalent to: 457: * <code>create(listenerInterface, target, action, null, null)</code></p> 458: * 459: * @param listenerInterface Listener interface to implement. 460: * @param target Object to invoke action on. 461: * @param action Target property or method to invoke. 462: * @return A constructed proxy object. 463: */ 464: public static <T> T create(Class<T> listenerInterface, Object target, 465: String action) 466: { 467: return create(listenerInterface, target, action, null, null); 468: } 469: 470: /** 471: * <p>Constructs an implementation of <code>listenerInterface</code> 472: * to dispatch events.</p> 473: * 474: * <p>Use this method if you want to create an implementation that retrieves 475: * a property value from the <b>first</b> argument of the listener method 476: * and applies it to the target's property or method. This first argument 477: * of the listener is usually an event object but any other object is 478: * valid, too.</p> 479: * 480: * <p>You can set the value of <code>eventPropertyName</code> to "prop" 481: * to denote the retrieval of a property named "prop" from the event 482: * object. In case that no such property exists the <code>EventHandler</code> 483: * will try to find a method with that name.</p> 484: * 485: * <p>If you set <code>eventPropertyName</code> to a value like this "a.b.c" 486: * <code>EventHandler</code> will recursively evaluate the properties "a", "b" 487: * and "c". Again if no property can be found the <code>EventHandler</code> 488: * tries a method name instead. This allows mixing the names, too: "a.toString" 489: * will retrieve the property "a" from the event object and will then call 490: * the method "toString" on it.</p> 491: * 492: * <p>An exception thrown in any of these methods will provoke a 493: * <code>RuntimeException</code> to be thrown which contains an 494: * <code>InvocationTargetException</code> containing the triggering exception.</p> 495: * 496: * <p>If you set <code>eventPropertyName</code> to a non-null value the 497: * <code>action</code> parameter will be interpreted as a property name 498: * or a method name of the target object.</p> 499: * 500: * <p>Any object retrieved from the event object and applied to the 501: * target will converted from primitives to their wrapper class or 502: * vice versa or applied to a method that accepts a superclass 503: * of the object.</p> 504: * 505: * <p>Examples:</p> 506: * <p>The following code:</p><code> 507: * button.addActionListener( 508: * new ActionListener() { 509: * public void actionPerformed(ActionEvent ae) { 510: * Object o = ae.getSource().getClass().getName(); 511: * textField.setText((String) o); 512: * } 513: * }); 514: * </code> 515: * 516: * <p>Can be expressed using the <code>EventHandler</code> like this:</p> 517: * <p> 518: * <code>button.addActionListener((ActionListener) 519: * EventHandler.create(ActionListener.class, textField, "text", "source.class.name"); 520: * <code> 521: * </p> 522: * 523: * <p>As said above you can specify the target as a method, too:</p> 524: * <p> 525: * <code>button.addActionListener((ActionListener) 526: * EventHandler.create(ActionListener.class, textField, "setText", "source.class.name"); 527: * <code> 528: * </p> 529: * 530: * <p>Furthermore you can use method names in the property:</p> 531: * <p> 532: * <code>button.addActionListener((ActionListener) 533: * EventHandler.create(ActionListener.class, textField, "setText", "getSource.getClass.getName"); 534: * <code> 535: * </p> 536: * 537: * <p>Finally you can mix names:</p> 538: * <p> 539: * <code>button.addActionListener((ActionListener) 540: * EventHandler.create(ActionListener.class, textField, "setText", "source.getClass.name"); 541: * <code> 542: * </p> 543: * 544: * <p>A call to this method is equivalent to: 545: * <code>create(listenerInterface, target, action, null, null)</code> 546: * </p> 547: * 548: * @param listenerInterface Listener interface to implement. 549: * @param target Object to invoke action on. 550: * @param action Target property or method to invoke. 551: * @param eventPropertyName Name of property to extract from event. 552: * @return A constructed proxy object. 553: */ 554: public static <T> T create(Class<T> listenerInterface, Object target, 555: String action, String eventPropertyName) 556: { 557: return create(listenerInterface, target, action, eventPropertyName, null); 558: } 559: 560: /** 561: * <p>Constructs an implementation of <code>listenerInterface</code> 562: * to dispatch events.</p> 563: * 564: * <p>Besides the functionality described for {@link create(Class, Object, String)} 565: * and {@link create(Class, Object, String, String)} this method allows you 566: * to filter the listener method that should have an effect. Look at these 567: * method's documentation for more information about the <code>EventHandler</code>'s 568: * usage.</p> 569: * 570: * <p>If you want to call <code>dispose</code> on a <code>JFrame</code> instance 571: * when the <code>WindowListener.windowClosing()</code> method was invoked use 572: * the following code:</p> 573: * <p> 574: * <code> 575: * EventHandler.create(WindowListener.class, jframeInstance, "dispose", null, "windowClosing"); 576: * </code> 577: * </p> 578: * 579: * <p>A <code>NullPointerException</code> is thrown if the <code>listenerInterface</code> 580: * or <code>target</code> argument are <code>null</code>. 581: * 582: * @param listenerInterface Listener interface to implement. 583: * @param target Object to invoke action on. 584: * @param action Target method name to invoke. 585: * @param eventPropertyName Name of property to extract from event. 586: * @param listenerMethodName Listener method to implement. 587: * @return A constructed proxy object. 588: */ 589: public static <T> T create(Class<T> listenerInterface, Object target, 590: String action, String eventPropertyName, 591: String listenerMethodName) 592: { 593: // Create EventHandler instance 594: EventHandler eh = new EventHandler(target, action, eventPropertyName, 595: listenerMethodName); 596: 597: // Create proxy object passing in the event handler 598: Object proxy = Proxy.newProxyInstance(listenerInterface.getClassLoader(), 599: new Class<?>[] {listenerInterface}, 600: eh); 601: 602: return (T) proxy; 603: } 604: }