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1: /* java.beans.Statement 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.Array; 42: import java.lang.reflect.Constructor; 43: import java.lang.reflect.Method; 44: 45: import java.util.HashMap; 46: import java.util.WeakHashMap; 47: 48: /** 49: * class Statement 50: * 51: * A Statement captures the execution of an object method. It stores 52: * the object, the method to call, and the arguments to the method and 53: * provides the ability to execute the method on the object, using the 54: * provided arguments. 55: * 56: * @since 1.4 57: */ 58: public class Statement 59: { 60: /** Nested map for the relation between a class, its instances and their 61: * names. 62: */ 63: private static HashMap classMaps = new HashMap(); 64: 65: private Object target; 66: private String methodName; 67: private Object[] arguments; 68: 69: // One or the other of these will get a value after execute is 70: // called once, but not both. 71: private transient Method method; 72: private transient Constructor ctor; 73: 74: /** 75: * <p>Constructs a statement representing the invocation of 76: * object.methodName(arg[0], arg[1], ...);</p> 77: * 78: * <p>If the argument array is null it is replaced with an 79: * array of zero length.</p> 80: * 81: * @param target The object to invoke the method on. 82: * @param methodName The object method to invoke. 83: * @param arguments An array of arguments to pass to the method. 84: */ 85: public Statement(Object target, String methodName, Object[] arguments) 86: { 87: this.target = target; 88: this.methodName = methodName; 89: this.arguments = (arguments != null) ? arguments : new Object[0]; 90: storeTargetName(target); 91: } 92: 93: /** Creates a name for the target instance or does nothing if the object's 94: * name is already known. This makes sure that there *is* a name for every 95: * target instance. 96: */ 97: private static synchronized void storeTargetName(Object obj) 98: { 99: Class klass = obj.getClass(); 100: WeakHashMap names = (WeakHashMap) classMaps.get(klass); 101: 102: if ( names == null ) 103: { 104: names = new WeakHashMap(); 105: 106: names.put(obj, 107: ( klass == String.class ? ("\"" + obj + "\"") : 108: (klass.getName() + names.size()) )); 109: 110: classMaps.put(klass, names); 111: 112: return; 113: } 114: 115: String targetName = (String) names.get(obj); 116: if ( targetName == null ) 117: { 118: names.put(obj, 119: ( klass == String.class ? ("\"" + obj + "\"") : 120: (klass.getName() + names.size()) )); 121: } 122: 123: // Nothing to do. The given object was already stored. 124: } 125: 126: /** 127: * Execute the statement. 128: * 129: * Finds the specified method in the target object and calls it with 130: * the arguments given in the constructor. 131: * 132: * The most specific method according to the JLS(15.11) is used when 133: * there are multiple methods with the same name. 134: * 135: * Execute performs some special handling for methods and 136: * parameters: 137: * 138: * Static methods can be executed by providing the class as a 139: * target. 140: * 141: * The method name new is reserved to call the constructor 142: * new() will construct an object and return it. Not useful unless 143: * an expression :-) 144: * 145: * If the target is an array, get and set as defined in 146: * java.util.List are recognized as valid methods and mapped to the 147: * methods of the same name in java.lang.reflect.Array. 148: * 149: * The native datatype wrappers Boolean, Byte, Character, Double, 150: * Float, Integer, Long, and Short will map to methods that have 151: * native datatypes as parameters, in the same way as Method.invoke. 152: * However, these wrappers also select methods that actually take 153: * the wrapper type as an argument. 154: * 155: * The Sun spec doesn't deal with overloading between int and 156: * Integer carefully. If there are two methods, one that takes an 157: * Integer and the other taking an int, the method chosen is not 158: * specified, and can depend on the order in which the methods are 159: * declared in the source file. 160: * 161: * @throws Exception if an exception occurs while locating or 162: * invoking the method. 163: */ 164: public void execute() throws Exception 165: { 166: doExecute(); 167: } 168: 169: private static Class wrappers[] = 170: { 171: Boolean.class, Byte.class, Character.class, Double.class, Float.class, 172: Integer.class, Long.class, Short.class 173: }; 174: 175: private static Class natives[] = 176: { 177: Boolean.TYPE, Byte.TYPE, Character.TYPE, Double.TYPE, Float.TYPE, 178: Integer.TYPE, Long.TYPE, Short.TYPE 179: }; 180: 181: // Given a wrapper class, return the native class for it. For 182: // example, if c is Integer, Integer.TYPE is returned. 183: private Class unwrap(Class c) 184: { 185: for (int i = 0; i < wrappers.length; i++) 186: if (c == wrappers[i]) 187: return natives[i]; 188: return null; 189: } 190: 191: // Return true if all args can be assigned to params, false 192: // otherwise. Arrays are guaranteed to be the same length. 193: private boolean compatible(Class[] params, Class[] args) 194: { 195: for (int i = 0; i < params.length; i++) 196: { 197: // Treat Integer like int if appropriate 198: Class nativeType = unwrap(args[i]); 199: if (nativeType != null && params[i].isPrimitive() 200: && params[i].isAssignableFrom(nativeType)) 201: continue; 202: if (params[i].isAssignableFrom(args[i])) 203: continue; 204: 205: return false; 206: } 207: return true; 208: } 209: 210: /** 211: * Return true if the method arguments in first are more specific 212: * than the method arguments in second, i.e. all args in first can 213: * be assigned to those in second. 214: * 215: * A method is more specific if all parameters can also be fed to 216: * the less specific method, because, e.g. the less specific method 217: * accepts a base class of the equivalent argument for the more 218: * specific one. 219: * 220: * @param first a <code>Class[]</code> value 221: * @param second a <code>Class[]</code> value 222: * @return a <code>boolean</code> value 223: */ 224: private boolean moreSpecific(Class[] first, Class[] second) 225: { 226: for (int j=0; j < first.length; j++) 227: { 228: if (second[j].isAssignableFrom(first[j])) 229: continue; 230: return false; 231: } 232: return true; 233: } 234: 235: final Object doExecute() throws Exception 236: { 237: Class klazz = (target instanceof Class) 238: ? (Class) target : target.getClass(); 239: Object args[] = (arguments == null) ? new Object[0] : arguments; 240: Class argTypes[] = new Class[args.length]; 241: for (int i = 0; i < args.length; i++) 242: argTypes[i] = args[i].getClass(); 243: 244: if (target.getClass().isArray()) 245: { 246: // FIXME: invoke may have to be used. For now, cast to Number 247: // and hope for the best. If caller didn't behave, we go boom 248: // and throw the exception. 249: if (methodName.equals("get") && argTypes.length == 1) 250: return Array.get(target, ((Number)args[0]).intValue()); 251: if (methodName.equals("set") && argTypes.length == 2) 252: { 253: Object obj = Array.get(target, ((Number)args[0]).intValue()); 254: Array.set(target, ((Number)args[0]).intValue(), args[1]); 255: return obj; 256: } 257: throw new NoSuchMethodException("No matching method for statement " + toString()); 258: } 259: 260: // If we already cached the method, just use it. 261: if (method != null) 262: return method.invoke(target, args); 263: else if (ctor != null) 264: return ctor.newInstance(args); 265: 266: // Find a matching method to call. JDK seems to go through all 267: // this to find the method to call. 268: 269: // if method name or length don't match, skip 270: // Need to go through each arg 271: // If arg is wrapper - check if method arg is matchable builtin 272: // or same type or super 273: // - check that method arg is same or super 274: 275: if (methodName.equals("new") && target instanceof Class) 276: { 277: Constructor ctors[] = klazz.getConstructors(); 278: for (int i = 0; i < ctors.length; i++) 279: { 280: // Skip methods with wrong number of args. 281: Class ptypes[] = ctors[i].getParameterTypes(); 282: 283: if (ptypes.length != args.length) 284: continue; 285: 286: // Check if method matches 287: if (!compatible(ptypes, argTypes)) 288: continue; 289: 290: // Use method[i] if it is more specific. 291: // FIXME: should this check both directions and throw if 292: // neither is more specific? 293: if (ctor == null) 294: { 295: ctor = ctors[i]; 296: continue; 297: } 298: Class mptypes[] = ctor.getParameterTypes(); 299: if (moreSpecific(ptypes, mptypes)) 300: ctor = ctors[i]; 301: } 302: if (ctor == null) 303: throw new InstantiationException("No matching constructor for statement " + toString()); 304: return ctor.newInstance(args); 305: } 306: 307: Method methods[] = klazz.getMethods(); 308: 309: for (int i = 0; i < methods.length; i++) 310: { 311: // Skip methods with wrong name or number of args. 312: if (!methods[i].getName().equals(methodName)) 313: continue; 314: Class ptypes[] = methods[i].getParameterTypes(); 315: if (ptypes.length != args.length) 316: continue; 317: 318: // Check if method matches 319: if (!compatible(ptypes, argTypes)) 320: continue; 321: 322: // Use method[i] if it is more specific. 323: // FIXME: should this check both directions and throw if 324: // neither is more specific? 325: if (method == null) 326: { 327: method = methods[i]; 328: continue; 329: } 330: Class mptypes[] = method.getParameterTypes(); 331: if (moreSpecific(ptypes, mptypes)) 332: method = methods[i]; 333: } 334: if (method == null) 335: throw new NoSuchMethodException("No matching method for statement " + toString()); 336: return method.invoke(target, args); 337: } 338: 339: 340: 341: /** Return the statement arguments. */ 342: public Object[] getArguments() { return arguments; } 343: 344: /** Return the statement method name. */ 345: public String getMethodName() { return methodName; } 346: 347: /** Return the statement object. */ 348: public Object getTarget() { return target; } 349: 350: /** Return a string representation. */ 351: public String toString() 352: { 353: StringBuffer result = new StringBuffer(); 354: 355: Class klass = target.getClass(); 356: 357: result.append( ((WeakHashMap) classMaps.get(klass)).get(target)); 358: result.append("."); 359: result.append(methodName); 360: result.append("("); 361: 362: String sep = ""; 363: for (int i = 0; i < arguments.length; i++) 364: { 365: result.append(sep); 366: result.append(arguments[i].getClass().getName()); 367: sep = ", "; 368: } 369: result.append(")"); 370: 371: return result.toString(); 372: } 373: }