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1: /* java.beans.PropertyDescriptor 2: Copyright (C) 1998, 2001, 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: package java.beans; 39: 40: import java.lang.reflect.Constructor; 41: import java.lang.reflect.InvocationTargetException; 42: import java.lang.reflect.Method; 43: 44: /** 45: ** PropertyDescriptor describes information about a JavaBean property, 46: ** by which we mean a property that has been exposed via a pair of 47: ** get and set methods. (There may be no get method, which means 48: ** the property is write-only, or no set method, which means the 49: ** the property is read-only.)<P> 50: ** 51: ** The constraints put on get and set methods are:<P> 52: ** <OL> 53: ** <LI>A get method must have signature 54: ** <CODE><propertyType> <getMethodName>()</CODE></LI> 55: ** <LI>A set method must have signature 56: ** <CODE>void <setMethodName>(<propertyType>)</CODE></LI> 57: ** <LI>Either method type may throw any exception.</LI> 58: ** <LI>Both methods must be public.</LI> 59: ** </OL> 60: ** 61: ** @author John Keiser 62: ** @author Robert Schuster (thebohemian@gmx.net) 63: ** @since 1.1 64: ** @status updated to 1.4 65: **/ 66: public class PropertyDescriptor extends FeatureDescriptor 67: { 68: Class<?> propertyType; 69: Method getMethod; 70: Method setMethod; 71: 72: Class<?> propertyEditorClass; 73: boolean bound; 74: boolean constrained; 75: 76: PropertyDescriptor(String name) 77: { 78: setName(name); 79: } 80: 81: /** Create a new PropertyDescriptor by introspection. 82: ** This form of constructor creates the PropertyDescriptor by 83: ** looking for a getter method named <CODE>get<name>()</CODE> 84: ** (or, optionally, if the property is boolean, 85: ** <CODE>is<name>()</CODE>) and 86: ** <CODE>set<name>()</CODE> in class 87: ** <CODE><beanClass></CODE>, where <name> has its 88: ** first letter capitalized by the constructor.<P> 89: ** 90: ** Note that using this constructor the given property must be read- <strong>and</strong> 91: ** writeable. If the implementation does not both, a read and a write method, an 92: ** <code>IntrospectionException</code> is thrown. 93: ** 94: ** <B>Implementation note:</B> If there is both are both isXXX and 95: ** getXXX methods, the former is used in preference to the latter. 96: ** We do not check that an isXXX method returns a boolean. In both 97: ** cases, this matches the behaviour of JDK 1.4<P> 98: ** 99: ** @param name the programmatic name of the property, usually 100: ** starting with a lowercase letter (e.g. fooManChu 101: ** instead of FooManChu). 102: ** @param beanClass the class the get and set methods live in. 103: ** @exception IntrospectionException if the methods are not found 104: ** or invalid. 105: **/ 106: public PropertyDescriptor(String name, Class<?> beanClass) 107: throws IntrospectionException 108: { 109: setName(name); 110: if (name.length() == 0) 111: { 112: throw new IntrospectionException("empty property name"); 113: } 114: String caps = Character.toUpperCase(name.charAt(0)) + name.substring(1); 115: findMethods(beanClass, "is" + caps, "get" + caps, "set" + caps); 116: 117: if (getMethod == null) 118: { 119: throw new IntrospectionException( 120: "Cannot find a is" + caps + " or get" + caps + " method"); 121: } 122: 123: if (setMethod == null) 124: { 125: throw new IntrospectionException( 126: "Cannot find a " + caps + " method"); 127: } 128: 129: // finally check the methods compatibility 130: propertyType = checkMethods(getMethod, setMethod); 131: } 132: 133: /** Create a new PropertyDescriptor by introspection. 134: ** This form of constructor allows you to specify the 135: ** names of the get and set methods to search for.<P> 136: ** 137: ** <B>Implementation note:</B> If there is a get method (or 138: ** boolean isXXX() method), then the return type of that method 139: ** is used to find the set method. If there is no get method, 140: ** then the set method is searched for exhaustively.<P> 141: ** 142: ** <B>Spec note:</B> 143: ** If there is no get method and multiple set methods with 144: ** the same name and a single parameter (different type of course), 145: ** then an IntrospectionException is thrown. While Sun's spec 146: ** does not state this, it can make Bean behavior different on 147: ** different systems (since method order is not guaranteed) and as 148: ** such, can be treated as a bug in the spec. I am not aware of 149: ** whether Sun's implementation catches this. 150: ** 151: ** @param name the programmatic name of the property, usually 152: ** starting with a lowercase letter (e.g. fooManChu 153: ** instead of FooManChu). 154: ** @param beanClass the class the get and set methods live in. 155: ** @param getMethodName the name of the get method or <code>null</code> if the property is write-only. 156: ** @param setMethodName the name of the set method or <code>null</code> if the property is read-only. 157: ** @exception IntrospectionException if the methods are not found 158: ** or invalid. 159: **/ 160: public PropertyDescriptor( 161: String name, 162: Class<?> beanClass, 163: String getMethodName, 164: String setMethodName) 165: throws IntrospectionException 166: { 167: setName(name); 168: findMethods(beanClass, getMethodName, null, setMethodName); 169: 170: if (getMethod == null && getMethodName != null) 171: { 172: throw new IntrospectionException( 173: "Cannot find a getter method called " + getMethodName); 174: } 175: 176: if (setMethod == null && setMethodName != null) 177: { 178: throw new IntrospectionException( 179: "Cannot find a setter method called " + setMethodName); 180: } 181: 182: propertyType = checkMethods(getMethod, setMethod); 183: } 184: 185: /** Create a new PropertyDescriptor using explicit Methods. 186: ** Note that the methods will be checked for conformance to standard 187: ** Property method rules, as described above at the top of this class. 188: **<br> 189: ** It is possible to call this method with both <code>Method</code> arguments 190: ** being <code>null</code>. In such a case the property type is <code>null</code>. 191: ** 192: ** @param name the programmatic name of the property, usually 193: ** starting with a lowercase letter (e.g. fooManChu 194: ** instead of FooManChu). 195: ** @param readMethod the read method or <code>null</code> if the property is write-only. 196: ** @param writeMethod the write method or <code>null</code> if the property is read-only. 197: ** @exception IntrospectionException if the methods are not found 198: ** or invalid. 199: **/ 200: public PropertyDescriptor( 201: String name, 202: Method readMethod, 203: Method writeMethod) 204: throws IntrospectionException 205: { 206: setName(name); 207: getMethod = readMethod; 208: setMethod = writeMethod; 209: propertyType = checkMethods(getMethod, setMethod); 210: } 211: 212: /** Get the property type. 213: ** This is the type the get method returns and the set method 214: ** takes in. 215: **/ 216: public Class<?> getPropertyType() 217: { 218: return propertyType; 219: } 220: 221: /** Get the get method. Why they call it readMethod here and 222: ** get everywhere else is beyond me. 223: **/ 224: public Method getReadMethod() 225: { 226: return getMethod; 227: } 228: 229: /** Sets the read method.<br/> 230: * The read method is used to retrieve the value of a property. A legal 231: * read method must have no arguments. Its return type must not be 232: * <code>void</code>. If this methods succeeds the property type 233: * is adjusted to the return type of the read method.<br/> 234: * <br/> 235: * It is legal to set the read and the write method to <code>null</code> 236: * or provide method which have been declared in distinct classes. 237: * 238: * @param readMethod The new method to be used or <code>null</code>. 239: * @throws IntrospectionException If the given method is invalid. 240: * @since 1.2 241: */ 242: public void setReadMethod(Method readMethod) throws IntrospectionException 243: { 244: propertyType = checkMethods(readMethod, setMethod); 245: 246: getMethod = readMethod; 247: } 248: 249: /** Get the set method. Why they call it writeMethod here and 250: ** set everywhere else is beyond me. 251: **/ 252: public Method getWriteMethod() 253: { 254: return setMethod; 255: } 256: 257: /** Sets the write method.<br/> 258: * The write method is used to set the value of a property. A legal write method 259: * must have a single argument which can be assigned to the property. If no 260: * read method exists the property type changes to the argument type of the 261: * write method.<br/> 262: * <br/> 263: * It is legal to set the read and the write method to <code>null</code> 264: * or provide method which have been declared in distinct classes. 265: * 266: * @param writeMethod The new method to be used or <code>null</code>. 267: * @throws IntrospectionException If the given method is invalid. 268: * @since 1.2 269: */ 270: public void setWriteMethod(Method writeMethod) 271: throws IntrospectionException 272: { 273: propertyType = checkMethods(getMethod, writeMethod); 274: 275: setMethod = writeMethod; 276: } 277: 278: /** Get whether the property is bound. Defaults to false. **/ 279: public boolean isBound() 280: { 281: return bound; 282: } 283: 284: /** Set whether the property is bound. 285: ** As long as the the bean implements addPropertyChangeListener() and 286: ** removePropertyChangeListener(), setBound(true) may safely be called.<P> 287: ** If these things are not true, then the behavior of the system 288: ** will be undefined.<P> 289: ** 290: ** When a property is bound, its set method is required to fire the 291: ** <CODE>PropertyChangeListener.propertyChange())</CODE> event 292: ** after the value has changed. 293: ** @param bound whether the property is bound or not. 294: **/ 295: public void setBound(boolean bound) 296: { 297: this.bound = bound; 298: } 299: 300: /** Get whether the property is constrained. Defaults to false. **/ 301: public boolean isConstrained() 302: { 303: return constrained; 304: } 305: 306: /** Set whether the property is constrained. 307: ** If the set method throws <CODE>java.beans.PropertyVetoException</CODE> 308: ** (or subclass thereof) and the bean implements addVetoableChangeListener() 309: ** and removeVetoableChangeListener(), then setConstrained(true) may safely 310: ** be called. Otherwise, the system behavior is undefined. 311: ** <B>Spec note:</B> given those strict parameters, it would be nice if it 312: ** got set automatically by detection, but oh well.<P> 313: ** When a property is constrained, its set method is required to:<P> 314: ** <OL> 315: ** <LI>Fire the <CODE>VetoableChangeListener.vetoableChange()</CODE> 316: ** event notifying others of the change and allowing them a chance to 317: ** say it is a bad thing.</LI> 318: ** <LI>If any of the listeners throws a PropertyVetoException, then 319: ** it must fire another vetoableChange() event notifying the others 320: ** of a reversion to the old value (though, of course, the change 321: ** was never made). Then it rethrows the PropertyVetoException and 322: ** exits.</LI> 323: ** <LI>If all has gone well to this point, the value may be changed.</LI> 324: ** </OL> 325: ** @param constrained whether the property is constrained or not. 326: **/ 327: public void setConstrained(boolean constrained) 328: { 329: this.constrained = constrained; 330: } 331: 332: /** Get the PropertyEditor class. Defaults to null. **/ 333: public Class<?> getPropertyEditorClass() 334: { 335: return propertyEditorClass; 336: } 337: 338: /** Set the PropertyEditor class. If the class does not implement 339: ** the PropertyEditor interface, you will likely get an exception 340: ** late in the game. 341: ** @param propertyEditorClass the PropertyEditor class for this 342: ** class to use. 343: **/ 344: public void setPropertyEditorClass(Class<?> propertyEditorClass) 345: { 346: this.propertyEditorClass = propertyEditorClass; 347: } 348: 349: /** 350: * Instantiate a property editor using the property editor class. 351: * If no property editor class has been set, this will return null. 352: * If the editor class has a public constructor which takes a single 353: * argument, that will be used and the bean parameter will be passed 354: * to it. Otherwise, a public no-argument constructor will be used, 355: * if available. This method will return null if no constructor is 356: * found or if construction fails for any reason. 357: * @param bean the argument to the constructor 358: * @return a new PropertyEditor, or null on error 359: * @since 1.5 360: */ 361: public PropertyEditor createPropertyEditor(Object bean) 362: { 363: if (propertyEditorClass == null) 364: return null; 365: Constructor c = findConstructor(propertyEditorClass, 366: new Class[] { Object.class }); 367: if (c != null) 368: return instantiateClass(c, new Object[] { bean }); 369: c = findConstructor(propertyEditorClass, null); 370: if (c != null) 371: return instantiateClass(c, null); 372: return null; 373: } 374: 375: // Helper method to look up a constructor and return null if it is not 376: // found. 377: private Constructor findConstructor(Class k, Class[] argTypes) 378: { 379: try 380: { 381: return k.getConstructor(argTypes); 382: } 383: catch (NoSuchMethodException _) 384: { 385: return null; 386: } 387: } 388: 389: // Helper method to instantiate an object but return null on error. 390: private PropertyEditor instantiateClass(Constructor c, Object[] args) 391: { 392: try 393: { 394: return (PropertyEditor) c.newInstance(args); 395: } 396: catch (InstantiationException _) 397: { 398: return null; 399: } 400: catch (InvocationTargetException _) 401: { 402: return null; 403: } 404: catch (IllegalAccessException _) 405: { 406: return null; 407: } 408: catch (ClassCastException _) 409: { 410: return null; 411: } 412: } 413: 414: private void findMethods( 415: Class beanClass, 416: String getMethodName1, 417: String getMethodName2, 418: String setMethodName) 419: throws IntrospectionException 420: { 421: try 422: { 423: // Try the first get method name 424: if (getMethodName1 != null) 425: { 426: try 427: { 428: getMethod = 429: beanClass.getMethod(getMethodName1, new Class[0]); 430: } 431: catch (NoSuchMethodException e) 432: {} 433: } 434: 435: // Fall back to the second get method name 436: if (getMethod == null && getMethodName2 != null) 437: { 438: try 439: { 440: getMethod = 441: beanClass.getMethod(getMethodName2, new Class[0]); 442: } 443: catch (NoSuchMethodException e) 444: {} 445: } 446: 447: // Try the set method name 448: if (setMethodName != null) 449: { 450: if (getMethod != null) 451: { 452: // If there is a get method, use its return type to help 453: // select the corresponding set method. 454: Class propertyType = getMethod.getReturnType(); 455: if (propertyType == Void.TYPE) 456: { 457: String msg = 458: "The property's read method has return type 'void'"; 459: throw new IntrospectionException(msg); 460: } 461: 462: Class[] setArgs = new Class[] { propertyType }; 463: try 464: { 465: setMethod = beanClass.getMethod(setMethodName, setArgs); 466: } 467: catch (NoSuchMethodException e) 468: {} 469: } 470: else if (getMethodName1 == null && getMethodName2 == null) 471: { 472: // If this is a write-only property, choose the first set method 473: // with the required name, one parameter and return type 'void' 474: Method[] methods = beanClass.getMethods(); 475: for (int i = 0; i < methods.length; i++) 476: { 477: if (methods[i].getName().equals(setMethodName) 478: && methods[i].getParameterTypes().length == 1 479: && methods[i].getReturnType() == Void.TYPE) 480: { 481: setMethod = methods[i]; 482: break; 483: } 484: } 485: } 486: } 487: } 488: catch (SecurityException e) 489: { 490: // FIXME -- shouldn't we just allow SecurityException to propagate? 491: String msg = 492: "SecurityException thrown on attempt to access methods."; 493: throw new IntrospectionException(msg); 494: } 495: } 496: 497: /** Checks whether the given <code>Method</code> instances are legal read and 498: * write methods. The following requirements must be met:<br/> 499: * <ul> 500: * <li>the read method must not have an argument</li> 501: * <li>the read method must have a non void return type</li> 502: * <li>the read method may not exist</li> 503: * <li>the write method must have a single argument</li> 504: * <li>the property type and the read method's return type must be assignable from the 505: * write method's argument type</li> 506: * <li>the write method may not exist</li> 507: * </ul> 508: * While checking the methods a common new property type is calculated. If the method 509: * succeeds this property type is returned.<br/> 510: * <br/> 511: * For compatibility this has to be noted:<br/> 512: * The two methods are allowed to be defined in two distinct classes and may both be null. 513: * 514: * @param readMethod The new read method to check. 515: * @param writeMethod The new write method to check. 516: * @return The common property type of the two method. 517: * @throws IntrospectionException If any of the above requirements are not met. 518: */ 519: private Class<?> checkMethods(Method readMethod, Method writeMethod) 520: throws IntrospectionException 521: { 522: Class<?> newPropertyType = propertyType; 523: 524: // a valid read method has zero arguments and a non-void return type. 525: if (readMethod != null) 526: { 527: if (readMethod.getParameterTypes().length > 0) 528: { 529: throw new IntrospectionException("read method has unexpected parameters"); 530: } 531: 532: newPropertyType = readMethod.getReturnType(); 533: 534: if (newPropertyType == Void.TYPE) 535: { 536: throw new IntrospectionException("read method return type is void"); 537: } 538: } 539: 540: // a valid write method has one argument which can be assigned to the property 541: if (writeMethod != null) 542: { 543: if (writeMethod.getParameterTypes().length != 1) 544: { 545: String msg = "write method does not have exactly one parameter"; 546: throw new IntrospectionException(msg); 547: } 548: 549: if (readMethod == null) 550: { 551: // changes the property type if there is no read method 552: newPropertyType = writeMethod.getParameterTypes()[0]; 553: } 554: else 555: { 556: // checks whether the write method can be assigned to the return type of the read 557: // method (if this is not the case, the methods are not compatible) 558: // note: newPropertyType may be null if no methods or method names have been 559: // delivered in the constructor. 560: if (newPropertyType != null 561: && !newPropertyType.isAssignableFrom( 562: writeMethod.getParameterTypes()[0])) 563: { 564: // note: newPropertyType is the same as readMethod.getReturnType() at this point 565: throw new IntrospectionException("read and write method are not compatible"); 566: } 567: 568: /* note: the check whether both method are defined in related classes makes sense but is not 569: * done in the JDK. 570: * I leave this code here in case someone at Sun decides to add that functionality in later versions (rschuster) 571: if ((!readMethod 572: .getDeclaringClass() 573: .isAssignableFrom(writeMethod.getDeclaringClass())) 574: && (!writeMethod 575: .getDeclaringClass() 576: .isAssignableFrom(readMethod.getDeclaringClass()))) 577: { 578: String msg = 579: "set and get methods are not in the same class."; 580: throw new IntrospectionException(msg); 581: } 582: */ 583: 584: } 585: } 586: 587: return newPropertyType; 588: } 589: 590: /** 591: * Return a hash code for this object, conforming to the contract described 592: * in {@link Object#hashCode()}. 593: * @return the hash code 594: * @since 1.5 595: */ 596: public int hashCode() 597: { 598: return ((propertyType == null ? 0 : propertyType.hashCode()) 599: | (propertyEditorClass == null ? 0 : propertyEditorClass.hashCode()) 600: | (bound ? Boolean.TRUE : Boolean.FALSE).hashCode() 601: | (constrained ? Boolean.TRUE : Boolean.FALSE).hashCode() 602: | (getMethod == null ? 0 : getMethod.hashCode()) 603: | (setMethod == null ? 0 : setMethod.hashCode())); 604: } 605: 606: /** Compares this <code>PropertyDescriptor</code> against the 607: * given object. 608: * Two PropertyDescriptors are equals if 609: * <ul> 610: * <li>the read methods are equal</li> 611: * <li>the write methods are equal</li> 612: * <li>the property types are equals</li> 613: * <li>the property editor classes are equal</li> 614: * <li>the flags (constrained and bound) are equal</li> 615: * </ul> 616: * @return Whether both objects are equal according to the rules given above. 617: * @since 1.4 618: */ 619: public boolean equals(Object o) 620: { 621: if (o instanceof PropertyDescriptor) 622: { 623: PropertyDescriptor that = (PropertyDescriptor) o; 624: 625: // compares the property types and checks the case where both are null 626: boolean samePropertyType = 627: (propertyType == null) 628: ? that.propertyType == null 629: : propertyType.equals(that.propertyType); 630: 631: // compares the property editor classes and checks the case where both are null 632: boolean samePropertyEditorClass = 633: (propertyEditorClass == null) 634: ? that.propertyEditorClass == null 635: : propertyEditorClass.equals(that.propertyEditorClass); 636: 637: // compares the flags for equality 638: boolean sameFlags = 639: bound == that.bound && constrained == that.constrained; 640: 641: // compares the read methods and checks the case where both are null 642: boolean sameReadMethod = 643: (getMethod == null) 644: ? that.getMethod == null 645: : getMethod.equals(that.getMethod); 646: 647: boolean sameWriteMethod = 648: (setMethod == null) 649: ? that.setMethod == null 650: : setMethod.equals(that.setMethod); 651: 652: return samePropertyType 653: && sameFlags 654: && sameReadMethod 655: && sameWriteMethod 656: && samePropertyEditorClass; 657: } 658: else 659: { 660: return false; 661: } 662: 663: } 664: 665: }