Source for java.io.ObjectStreamField

   1: /* ObjectStreamField.java -- Class used to store name and class of fields
   2:    Copyright (C) 1998, 1999, 2003, 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.io;
  40: 
  41: import gnu.java.lang.reflect.TypeSignature;
  42: 
  43: import java.lang.reflect.Field;
  44: import java.security.AccessController;
  45: import java.security.PrivilegedAction;
  46: 
  47: /**
  48:  * This class intends to describe the field of a class for the serialization
  49:  * subsystem. Serializable fields in a serializable class can be explicitly
  50:  * exported using an array of ObjectStreamFields.
  51:  *
  52:  * @author Tom Tromey (tromey@redhat.com)
  53:  * @author Jeroen Frijters (jeroen@frijters.net)
  54:  * @author Guilhem Lavaux (guilhem@kaffe.org)
  55:  * @author Michael Koch (konqueror@gmx.de)
  56:  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  57:  */
  58: public class ObjectStreamField 
  59:   implements Comparable<Object>
  60: {
  61:   private String name;
  62:   private Class<?> type;
  63:   private String typename;
  64:   private int offset = -1; // XXX make sure this is correct
  65:   private boolean unshared;
  66:   private boolean persistent = false;
  67:   private boolean toset = true;
  68:   Field field;
  69: 
  70:   ObjectStreamField (Field field)
  71:   {
  72:     this (field.getName(), field.getType());
  73:     this.field = field;
  74:   }
  75: 
  76:   /**
  77:    * This constructor creates an ObjectStreamField instance 
  78:    * which represents a field named <code>name</code> and is
  79:    * of the type <code>type</code>.
  80:    *
  81:    * @param name Name of the field to export.
  82:    * @param type Type of the field in the concerned class.
  83:    */
  84:   public ObjectStreamField (String name, Class<?> type)
  85:   {
  86:     this (name, type, false);
  87:   }
  88: 
  89:   /**
  90:    * This constructor creates an ObjectStreamField instance 
  91:    * which represents a field named <code>name</code> and is
  92:    * of the type <code>type</code>.
  93:    *
  94:    * @param name Name of the field to export.
  95:    * @param type Type of the field in the concerned class.
  96:    * @param unshared true if field will be unshared, false otherwise.
  97:    */
  98:   public ObjectStreamField (String name, Class<?> type, boolean unshared)
  99:   {
 100:     if (name == null)
 101:       throw new NullPointerException();
 102: 
 103:     this.name = name;
 104:     this.type = type;
 105:     this.typename = TypeSignature.getEncodingOfClass(type);
 106:     this.unshared = unshared;
 107:   }
 108:  
 109:   /**
 110:    * There are many cases you can not get java.lang.Class from typename 
 111:    * if your context class loader cannot load it, then use typename to
 112:    * construct the field.
 113:    *
 114:    * @param name Name of the field to export.
 115:    * @param typename The coded name of the type for this field.
 116:    */
 117:   ObjectStreamField (String name, String typename)
 118:   {
 119:     this.name = name;
 120:     this.typename = typename;
 121:   }
 122: 
 123:   void resolveType(ClassLoader loader)
 124:   {
 125:     try
 126:       {
 127:         type = TypeSignature.getClassForEncoding(typename, true, loader);
 128:       }
 129:     catch(ClassNotFoundException e)
 130:       {
 131:       }
 132:   }
 133:   
 134:   /**
 135:    * This method returns the name of the field represented by the
 136:    * ObjectStreamField instance.
 137:    *
 138:    * @return A string containing the name of the field.
 139:    */
 140:   public String getName ()
 141:   {
 142:     return name;
 143:   }
 144: 
 145:   /**
 146:    * This method returns the class representing the type of the
 147:    * field which is represented by this instance of ObjectStreamField.
 148:    *
 149:    * @return A class representing the type of the field.
 150:    */
 151:   public Class<?> getType ()
 152:   {
 153:     return type;
 154:   }
 155: 
 156:   /**
 157:    * This method returns the char encoded type of the field which
 158:    * is represented by this instance of ObjectStreamField.
 159:    *
 160:    * @return A char representing the type of the field.
 161:    */
 162:   public char getTypeCode ()
 163:   {
 164:     return typename.charAt (0);
 165:   }
 166: 
 167:   /**
 168:    * This method returns a more explicit type name than
 169:    * {@link #getTypeCode()} in the case the type is a real
 170:    * class (and not a primitive).
 171:    *
 172:    * @return The name of the type (class name) if it is not a 
 173:    * primitive, in the other case null is returned.
 174:    */
 175:   public String getTypeString ()
 176:   {
 177:     // use intern()
 178:     if (isPrimitive())
 179:       return null;
 180:     return typename.intern();
 181:   }
 182: 
 183:   /**
 184:    * This method returns the current offset of the field in
 185:    * the serialization stream relatively to the other fields.
 186:    * The offset is expressed in bytes.
 187:    *
 188:    * @return The offset of the field in bytes.
 189:    * @see #setOffset(int)
 190:    */
 191:   public int getOffset ()
 192:   {
 193:     return offset;
 194:   }
 195: 
 196:   /**
 197:    * This method sets the current offset of the field.
 198:    * 
 199:    * @param off The offset of the field in bytes.
 200:    * @see #getOffset()
 201:    */
 202:   protected void setOffset (int off)
 203:   {
 204:     offset = off;
 205:   }
 206: 
 207:   /**
 208:    * This method returns whether the field represented by this object is
 209:    * unshared or not.
 210:    *
 211:    * @return Tells if this field is unshared or not.
 212:    */
 213:   public boolean isUnshared ()
 214:   {
 215:     return unshared;
 216:   }
 217: 
 218:   /**
 219:    * This method returns true if the type of the field
 220:    * represented by this instance is a primitive.
 221:    *
 222:    * @return true if the type is a primitive, false
 223:    * in the other case.
 224:    */
 225:   public boolean isPrimitive ()
 226:   {
 227:     return typename.length() == 1;
 228:   }
 229: 
 230:   /**
 231:    * Compares this object to the given object.
 232:    *
 233:    * @param obj the object to compare to.
 234:    *
 235:    * @return -1, 0 or 1.
 236:    */
 237:   public int compareTo (Object obj)
 238:   {
 239:     ObjectStreamField f = (ObjectStreamField) obj;
 240:     boolean this_is_primitive = isPrimitive ();
 241:     boolean f_is_primitive = f.isPrimitive ();
 242: 
 243:     if (this_is_primitive && !f_is_primitive)
 244:       return -1;
 245: 
 246:     if (!this_is_primitive && f_is_primitive)
 247:       return 1;
 248: 
 249:     return getName ().compareTo (f.getName ());
 250:   }
 251: 
 252:   /**
 253:    * This method is specific to classpath's implementation and so has the default
 254:    * access. It changes the state of this field to "persistent". It means that
 255:    * the field should not be changed when the stream is read (if it is not
 256:    * explicitly specified using serialPersistentFields).
 257:    *
 258:    * @param persistent True if the field is persistent, false in the 
 259:    * other cases.
 260:    * @see #isPersistent()
 261:    */
 262:   void setPersistent(boolean persistent)
 263:   {
 264:     this.persistent = persistent;
 265:   }
 266: 
 267:   /**
 268:    * This method returns true if the field is marked as persistent.
 269:    *
 270:    * @return True if persistent, false in the other cases.
 271:    * @see #setPersistent(boolean)
 272:    */
 273:   boolean isPersistent()
 274:   {
 275:     return persistent;
 276:   }
 277: 
 278:   /**
 279:    * This method is specific to classpath's implementation and so 
 280:    * has the default access. It changes the state of this field as
 281:    * to be set by ObjectInputStream.
 282:    *
 283:    * @param toset True if this field should be set, false in the other
 284:    * cases.
 285:    * @see #isToSet()
 286:    */
 287:   void setToSet(boolean toset)
 288:   {
 289:     this.toset = toset;
 290:   }
 291: 
 292:   /**
 293:    * This method returns true if the field is marked as to be
 294:    * set.
 295:    *
 296:    * @return True if it is to be set, false in the other cases.
 297:    * @see #setToSet(boolean)
 298:    */
 299:   boolean isToSet()
 300:   {
 301:     return toset;
 302:   }
 303: 
 304:   /**
 305:    * This method searches for its field reference in the specified class
 306:    * object. It requests privileges. If an error occurs the internal field
 307:    * reference is not modified.
 308:    *
 309:    * @throws NoSuchFieldException if the field name does not exist in this class.
 310:    * @throws SecurityException if there was an error requesting the privileges.
 311:    */
 312:   void lookupField(Class clazz) throws NoSuchFieldException, SecurityException
 313:   {
 314:     final Field f = clazz.getDeclaredField(name);
 315:     
 316:     AccessController.doPrivileged(new PrivilegedAction()
 317:       {
 318:     public Object run()
 319:     {
 320:       f.setAccessible(true);
 321:       return null;
 322:     }
 323:       });
 324:     
 325:     this.field = f;
 326:   }
 327: 
 328:   /**
 329:    * This method check whether the field described by this
 330:    * instance of ObjectStreamField is compatible with the
 331:    * actual implementation of this field.
 332:    *
 333:    * @throws NullPointerException if this field does not exist
 334:    * in the real class.
 335:    * @throws InvalidClassException if the types are incompatible.
 336:    */
 337:   void checkFieldType() throws InvalidClassException
 338:   {
 339:     Class<?> ftype = field.getType();
 340: 
 341:     if (!ftype.isAssignableFrom(type))
 342:       throw new InvalidClassException
 343:     ("invalid field type for " + name +
 344:      " in class " + field.getDeclaringClass());
 345:   }
 346: 
 347:   /**
 348:    * Returns a string representing this object.
 349:    *
 350:    * @return the string.
 351:    */
 352:   public String toString ()
 353:   {
 354:     return "ObjectStreamField< " + type + " " + name + " >";
 355:   }
 356: 
 357:   final void setBooleanField(Object obj, boolean val)
 358:   {
 359:     VMObjectStreamClass.setBooleanNative(field, obj, val);  
 360:   }
 361: 
 362:   final void setByteField(Object obj, byte val)
 363:   {
 364:     VMObjectStreamClass.setByteNative(field, obj, val);
 365:   }
 366:   
 367:   final void setCharField(Object obj, char val)
 368:   {
 369:     VMObjectStreamClass.setCharNative(field, obj, val);
 370:   }
 371:   
 372:   final void setShortField(Object obj, short val)
 373:   {
 374:     VMObjectStreamClass.setShortNative(field, obj, val);
 375:   }
 376: 
 377:   final void setIntField(Object obj, int val)
 378:   {
 379:     VMObjectStreamClass.setIntNative(field, obj, val);
 380:   }
 381:   
 382:   final void setLongField(Object obj, long val)
 383:   {
 384:     VMObjectStreamClass.setLongNative(field, obj, val);
 385:   }
 386:   
 387:   final void setFloatField(Object obj, float val)
 388:   {
 389:     VMObjectStreamClass.setFloatNative(field, obj, val);
 390:   }
 391:   
 392:   final void setDoubleField(Object obj, double val)
 393:   {
 394:     VMObjectStreamClass.setDoubleNative(field, obj, val);
 395:   }
 396:   
 397:   final void setObjectField(Object obj, Object val)
 398:   { 
 399:     VMObjectStreamClass.setObjectNative(field, obj, val);
 400:   }
 401: }