Source for java.beans.Statement

   1: /* java.beans.Statement
   2:    Copyright (C) 2004 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: /**
  46:  * class Statement
  47:  *
  48:  * A Statement captures the execution of an object method.  It stores
  49:  * the object, the method to call, and the arguments to the method and
  50:  * provides the ability to execute the method on the object, using the
  51:  * provided arguments.
  52:  *
  53:  * @since 1.4
  54:  */
  55: public class Statement
  56: {
  57:   private Object target;
  58:   private String methodName;
  59:   private Object[] arguments;
  60: 
  61:   // One or the other of these will get a value after execute is
  62:   // called once, but not both.
  63:   private transient Method method;
  64:   private transient Constructor ctor;
  65: 
  66:   /**
  67:    * Constructs a statement representing the invocation of
  68:    * object.methodName(arg[0], arg[1], ...);
  69:    *
  70:    * @param target The object to invoke the method on.
  71:    * @param methodName The object method to invoke.
  72:    * @param arguments An array of arguments to pass to the method.
  73:    */
  74:   public Statement(Object target, String methodName, Object[] arguments)
  75:   {
  76:     this.target = target;
  77:     this.methodName = methodName;
  78:     this.arguments = arguments;
  79:   }
  80: 
  81:   /**
  82:    * Execute the statement.
  83:    *
  84:    * Finds the specified method in the target object and calls it with
  85:    * the arguments given in the constructor.
  86:    *
  87:    * The most specific method according to the JLS(15.11) is used when
  88:    * there are multiple methods with the same name.
  89:    *
  90:    * Execute performs some special handling for methods and
  91:    * parameters:
  92:    *
  93:    * Static methods can be executed by providing the class as a
  94:    * target.
  95:    *
  96:    * The method name new is reserved to call the constructor 
  97:    * new() will construct an object and return it.  Not useful unless
  98:    * an expression :-)
  99:    *
 100:    * If the target is an array, get and set as defined in
 101:    * java.util.List are recognized as valid methods and mapped to the
 102:    * methods of the same name in java.lang.reflect.Array.
 103:    *
 104:    * The native datatype wrappers Boolean, Byte, Character, Double,
 105:    * Float, Integer, Long, and Short will map to methods that have
 106:    * native datatypes as parameters, in the same way as Method.invoke.
 107:    * However, these wrappers also select methods that actually take
 108:    * the wrapper type as an argument.
 109:    *
 110:    * The Sun spec doesn't deal with overloading between int and
 111:    * Integer carefully.  If there are two methods, one that takes an
 112:    * Integer and the other taking an int, the method chosen is not
 113:    * specified, and can depend on the order in which the methods are
 114:    * declared in the source file.
 115:    *
 116:    * @throws Exception if an exception occurs while locating or
 117:    *                invoking the method.
 118:    */
 119:   public void execute() throws Exception
 120:   {
 121:     doExecute();
 122:   }
 123:   
 124:   private static Class wrappers[] = 
 125:     {
 126:       Boolean.class, Byte.class, Character.class, Double.class, Float.class,
 127:       Integer.class, Long.class, Short.class
 128:     };
 129: 
 130:   private static Class natives[] = 
 131:     {
 132:       Boolean.TYPE, Byte.TYPE, Character.TYPE, Double.TYPE, Float.TYPE,
 133:       Integer.TYPE, Long.TYPE, Short.TYPE
 134:     };
 135: 
 136:   // Given a wrapper class, return the native class for it.  For
 137:   // example, if c is Integer, Integer.TYPE is returned.
 138:   private Class unwrap(Class c)
 139:   {
 140:     for (int i = 0; i < wrappers.length; i++)
 141:       if (c == wrappers[i])
 142:     return natives[i];
 143:     return null;
 144:   }
 145: 
 146:   // Return true if all args can be assigned to params, false
 147:   // otherwise.  Arrays are guaranteed to be the same length.
 148:   private boolean compatible(Class[] params, Class[] args)
 149:   {
 150:     for (int i = 0; i < params.length; i++)
 151:       {
 152:     // Treat Integer like int if appropriate
 153:     Class nativeType = unwrap(args[i]);
 154:     if (nativeType != null && params[i].isPrimitive()
 155:         && params[i].isAssignableFrom(nativeType))
 156:       continue;
 157:     if (params[i].isAssignableFrom(args[i]))
 158:       continue;
 159: 
 160:     return false;
 161:       }
 162:     return true;
 163:   }
 164: 
 165:   /**
 166:    * Return true if the method arguments in first are more specific
 167:    * than the method arguments in second, i.e. all args in first can
 168:    * be assigned to those in second.
 169:    *
 170:    * A method is more specific if all parameters can also be fed to
 171:    * the less specific method, because, e.g. the less specific method
 172:    * accepts a base class of the equivalent argument for the more
 173:    * specific one.
 174:    *
 175:    * @param first a <code>Class[]</code> value
 176:    * @param second a <code>Class[]</code> value
 177:    * @return a <code>boolean</code> value
 178:    */
 179:   private boolean moreSpecific(Class[] first, Class[] second)
 180:   {
 181:     for (int j=0; j < first.length; j++)
 182:       {
 183:     if (second[j].isAssignableFrom(first[j]))
 184:       continue;
 185:     return false;
 186:       }
 187:     return true;
 188:   }
 189: 
 190:   final Object doExecute() throws Exception
 191:   {
 192:     Class klazz = (target instanceof Class)
 193:     ? (Class) target : target.getClass();
 194:     Object args[] = (arguments == null) ? new Object[0] : arguments;
 195:     Class argTypes[] = new Class[args.length];
 196:     for (int i = 0; i < args.length; i++)
 197:       argTypes[i] = args[i].getClass();
 198: 
 199:     if (target.getClass().isArray())
 200:       {
 201:     // FIXME: invoke may have to be used.  For now, cast to Number
 202:     // and hope for the best.  If caller didn't behave, we go boom
 203:     // and throw the exception.
 204:     if (methodName.equals("get") && argTypes.length == 1)
 205:       return Array.get(target, ((Number)args[0]).intValue());
 206:     if (methodName.equals("set") && argTypes.length == 2)
 207:       {
 208:         Object obj = Array.get(target, ((Number)args[0]).intValue());
 209:         Array.set(target, ((Number)args[0]).intValue(), args[1]);
 210:         return obj;
 211:       }
 212:     throw new NoSuchMethodException("No matching method for statement " + toString());
 213:       }
 214: 
 215:     // If we already cached the method, just use it.
 216:     if (method != null)
 217:       return method.invoke(target, args);
 218:     else if (ctor != null)
 219:       return ctor.newInstance(args);
 220: 
 221:     // Find a matching method to call.  JDK seems to go through all
 222:     // this to find the method to call.
 223: 
 224:     // if method name or length don't match, skip
 225:     // Need to go through each arg
 226:     // If arg is wrapper - check if method arg is matchable builtin
 227:     //  or same type or super
 228:     //  - check that method arg is same or super
 229: 
 230:     if (methodName.equals("new") && target instanceof Class)
 231:       {
 232:     Constructor ctors[] = klazz.getConstructors();
 233:     for (int i = 0; i < ctors.length; i++)
 234:       {
 235:         // Skip methods with wrong number of args.
 236:         Class ptypes[] = ctors[i].getParameterTypes();
 237:         System.out.println("ptypeslen = " + ptypes.length);
 238:         System.out.println("ptypes = " + ptypes);
 239:         System.out.println("ctor = " + ctors[i].getName());
 240:         for (int j=0; j < ptypes.length; j++) {
 241:           System.out.println("param = " + ptypes[i].getName());
 242:      
 243:         }
 244:           
 245:         
 246:         if (ptypes.length != args.length)
 247:           continue;
 248: 
 249:         // Check if method matches
 250:         if (!compatible(ptypes, argTypes))
 251:           continue;
 252: 
 253:         // Use method[i] if it is more specific. 
 254:         // FIXME: should this check both directions and throw if
 255:         // neither is more specific?
 256:         if (ctor == null)
 257:           {
 258:         ctor = ctors[i];
 259:         continue;
 260:           }
 261:         Class mptypes[] = ctor.getParameterTypes();
 262:         if (moreSpecific(ptypes, mptypes))
 263:           ctor = ctors[i];
 264:       }
 265:     if (ctor == null)
 266:       throw new InstantiationException("No matching constructor for statement " + toString());
 267:     return ctor.newInstance(args);
 268:       }
 269: 
 270:     Method methods[] = klazz.getMethods();
 271: 
 272:     for (int i = 0; i < methods.length; i++)
 273:       {
 274:     // Skip methods with wrong name or number of args.
 275:     if (!methods[i].getName().equals(methodName))
 276:       continue;
 277:     Class ptypes[] = methods[i].getParameterTypes();
 278:     if (ptypes.length != args.length)
 279:       continue;
 280: 
 281:     // Check if method matches
 282:     if (!compatible(ptypes, argTypes))
 283:       continue;
 284: 
 285:     // Use method[i] if it is more specific. 
 286:     // FIXME: should this check both directions and throw if
 287:     // neither is more specific?
 288:     if (method == null)
 289:       {
 290:         method = methods[i];
 291:         continue;
 292:       }
 293:     Class mptypes[] = method.getParameterTypes();
 294:     if (moreSpecific(ptypes, mptypes))
 295:       method = methods[i];
 296:       }
 297:     if (method == null)
 298:       throw new NoSuchMethodException("No matching method for statement " + toString());
 299:     return method.invoke(target, args);
 300:   }
 301: 
 302:   
 303: 
 304:   /** Return the statement arguments. */
 305:   public Object[] getArguments() { return arguments; }
 306: 
 307:   /** Return the statement method name. */
 308:   public String getMethodName() { return methodName; }
 309: 
 310:   /** Return the statement object. */
 311:   public Object getTarget() { return target; }
 312: 
 313:   /** Return a string representation. */
 314:   public String toString()
 315:   {
 316:     String result = target.getClass().getName() + "." + methodName + "(";
 317:     String sep = "";
 318:     for (int i = 0; i < arguments.length; i++)
 319:       {
 320:     result = result + sep + arguments[i].getClass().getName();
 321:     sep = ", ";
 322:       }
 323:     result = result + ")";
 324:     return result;
 325:   }
 326: }