001 /* ArrayType.java -- Open type descriptor for an array.
002 Copyright (C) 2006, 2007 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package javax.management.openmbean;
039
040 import java.lang.reflect.Array;
041
042 import java.util.Arrays;
043 import java.util.HashMap;
044 import java.util.Map;
045
046 /**
047 * The open type descriptor for arrays of open data values.
048 *
049 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
050 * @since 1.5
051 */
052 public class ArrayType<T>
053 extends OpenType<T>
054 {
055
056 /**
057 * Compatible with JDK 1.5
058 */
059 private static final long serialVersionUID = 720504429830309770L;
060
061 /**
062 * The number of dimensions arrays of this type has.
063 */
064 private int dimension;
065
066 /**
067 * The element type of arrays of this type.
068 */
069 private OpenType<?> elementType;
070
071 /**
072 * True if this type represents a primitive array.
073 */
074 private boolean primitiveArray;
075
076 /**
077 * The hash code of this instance.
078 */
079 private transient Integer hashCode;
080
081 /**
082 * The <code>toString()</code> result of this instance.
083 */
084 private transient String string;
085
086 /**
087 * A cache of {@link ArrayType} instances created
088 * by {@link #getArrayType(OpenType)}.
089 */
090 private static final Map<OpenType<?>,ArrayType<?>> cache =
091 new HashMap<OpenType<?>,ArrayType<?>>();
092
093 /**
094 * A cache of {@link ArrayType} instances created
095 * by {@link #getPrimitiveArrayType(Class)}.
096 */
097 private static final Map<Class<?>,ArrayType<?>> primCache =
098 new HashMap<Class<?>,ArrayType<?>>();
099
100 /**
101 * Returns the class name of the array, given the element
102 * class name and its dimensions.
103 *
104 * @param elementType the type of the array's elements.
105 * @param dim the dimensions of the array.
106 * @param primitive true if this should be a primitive array.
107 * @return the array's class name.
108 * @throws OpenDataException if the class name does not reference
109 * a loadable class.
110 */
111 private static final String getArrayClassName(OpenType<?> elementType,
112 int dim,
113 boolean primitive)
114 throws OpenDataException
115 {
116 Class<?> type;
117 if (primitive)
118 type = getPrimitiveTypeClass((SimpleType<?>) elementType);
119 else
120 {
121 String className = elementType.getClassName();
122 try
123 {
124 type = Class.forName(className);
125 }
126 catch (ClassNotFoundException e)
127 {
128 throw new OpenDataException("The class name, " + className +
129 ", is unavailable.");
130 }
131 }
132 while (type.isArray())
133 type = type.getComponentType();
134 return
135 Array.newInstance(type,
136 new int[getDimensions(elementType, dim)]).getClass().getName();
137 }
138
139 /**
140 * Returns the dimensions of the new {@link ArrayType},
141 * based on whether the given element type is already an
142 * {@link ArrayType} or not.
143 *
144 * @param elementType the type of the array.
145 * @param dim the proposed dimensions.
146 * @return the resultant dimensions.
147 * @throws IllegalArgumentException if <code>dim</code> is less than 1.
148 */
149 private static final int getDimensions(OpenType<?> elementType,
150 int dim)
151 {
152 if (dim < 1)
153 throw new IllegalArgumentException("Dimensions must be greater " +
154 "than or equal to 1.");
155 if (elementType instanceof ArrayType)
156 return dim + ((ArrayType) elementType).getDimension();
157 return dim;
158 }
159
160 /**
161 * Returns the appropriate primitive type name, given the
162 * corresponding wrapper class.
163 *
164 * @param type the type to convert.
165 * @return the corresponding primitive type.
166 * @throws OpenDataException if {@code type} is not a valid
167 * {@link Class} for a primitive type.
168 *
169 */
170 private static final SimpleType<?> getPrimitiveType(Class<?> type)
171 throws OpenDataException
172 {
173 if (type.equals(Boolean.TYPE))
174 return SimpleType.BOOLEAN;
175 if (type.equals(Byte.TYPE))
176 return SimpleType.BYTE;
177 if (type.equals(Character.TYPE))
178 return SimpleType.CHARACTER;
179 if (type.equals(Double.TYPE))
180 return SimpleType.DOUBLE;
181 if (type.equals(Float.TYPE))
182 return SimpleType.FLOAT;
183 if (type.equals(Integer.TYPE))
184 return SimpleType.INTEGER;
185 if (type.equals(Long.TYPE))
186 return SimpleType.LONG;
187 if (type.equals(Short.TYPE))
188 return SimpleType.SHORT;
189 if (type.equals(Void.TYPE))
190 return SimpleType.VOID;
191 throw new OpenDataException(type + " is not a primitive type.");
192 }
193
194 /**
195 * Returns the appropriate primitive type name, given the
196 * corresponding wrapper class.
197 *
198 * @param type the type to convert.
199 * @return the corresponding primitive type.
200 * @throws OpenDataException if {@code type} is not a valid
201 * {@link SimpleType} for a primitive type.
202 *
203 */
204 private static final Class<?> getPrimitiveTypeClass(SimpleType<?> type)
205 throws OpenDataException
206 {
207 if (type.equals(SimpleType.BOOLEAN))
208 return Boolean.TYPE;
209 if (type.equals(SimpleType.BYTE))
210 return Byte.TYPE;
211 if (type.equals(SimpleType.CHARACTER))
212 return Character.TYPE;
213 if (type.equals(SimpleType.DOUBLE))
214 return Double.TYPE;
215 if (type.equals(SimpleType.FLOAT))
216 return Float.TYPE;
217 if (type.equals(SimpleType.INTEGER))
218 return Integer.TYPE;
219 if (type.equals(SimpleType.LONG))
220 return Long.TYPE;
221 if (type.equals(SimpleType.SHORT))
222 return Short.TYPE;
223 if (type.equals(SimpleType.VOID))
224 return Void.TYPE;
225 throw new OpenDataException(type + " is not a primitive type.");
226 }
227
228 /**
229 * Returns the element type that will actually be used, if the
230 * specified element type is passed to a constructor. This is
231 * necessary to ensure that a non-array type is still returned when
232 * an {@link ArrayType} is constructed from an {@link ArrayType}.
233 *
234 * @param elemType the element type that was supplied.
235 * @return the element type that will be used.
236 */
237 private static final OpenType<?> getElementType(OpenType<?> elemType)
238 {
239 if (elemType instanceof ArrayType)
240 return ((ArrayType) elemType).getElementOpenType();
241 return elemType;
242 }
243
244 /**
245 * Returns the element type name that will actually be used, if the
246 * specified element type is passed to a constructor. This is
247 * necessary to ensure that a non-array type is still returned when
248 * an {@link ArrayType} is constructed from an {@link ArrayType},
249 * and that primitive arrays are described correctly.
250 *
251 * @param elemType the element type that was supplied.
252 * @return the element type name that will be used.
253 * @throws OpenDataException if the element type is not a valid
254 * {@link SimpleType} for a primitive type.
255 */
256 private static final String getElementTypeName(OpenType<?> elemType)
257 throws OpenDataException
258 {
259 OpenType<?> trueElemType = getElementType(elemType);
260 if (elemType instanceof ArrayType &&
261 ((ArrayType) elemType).isPrimitiveArray())
262 return getPrimitiveTypeClass((SimpleType<?>) trueElemType).getName();
263 return trueElemType.getClassName();
264 }
265
266 /**
267 * <p>
268 * Constructs a new {@link ArrayType} instance for an array of the
269 * specified type with the supplied number of dimensions. The attributes
270 * used by the superclass, {@link OpenType}, are automatically defined,
271 * based on these values. Both the class name and type name are set
272 * to the value returned by the {@link java.lang.Class#getName()} of
273 * the array's class (i.e. the element type, preceded by n instances of
274 * '[' and an 'L', where n is the number of dimensions the array has).
275 * The description is based upon the template <code>n-dimension array
276 * of e</code>, where n is the number of dimensions of the array, and
277 * e is the element type. The class name of the actual elements is
278 * obtainable by calling {@link OpenType#getClassName()} on the result
279 * of {@link #getElementOpenType()}.
280 * </p>
281 * <p>
282 * As an example, the array type returned by
283 * <code>new ArrayType(6, SimpleType.INTEGER)</code> has the following
284 * values:
285 * </p>
286 * <table>
287 * <th><td>Attribute</td><td>Value</td></th>
288 * <tr><td>Class Name</td><td><code>[[[[[[Ljava.lang.Integer;</code>
289 * </td></tr>
290 * <tr><td>Type Name</td><td><code>[[[[[[Ljava.lang.Integer;</code>
291 * </td></tr>
292 * <tr><td>Description</td><td><code>6-dimension array of
293 * java.lang.Integer</code></td></tr>
294 * <tr><td>Element Type Class Name</td><td><code>java.lang.Integer</code>
295 * </td></tr>
296 * </table>
297 * <p>
298 * The dimensions of the array must be equal to or greater than 1. The
299 * element type must be an instance of {@link SimpleType},
300 * {@link CompositeType} or {@link TabularType}.
301 * </p>
302 *
303 * @param dim the dimensions of the array.
304 * @param elementType the type of the elements of the array.
305 * @throws IllegalArgumentException if <code>dim</code> is less than 1.
306 * @throws OpenDataException if the element type is not an instance of either
307 * {@link SimpleType}, {@link CompositeType}
308 * or {@link TabularType}.
309 */
310 public ArrayType(int dim, OpenType<?> elementType)
311 throws OpenDataException
312 {
313 super(getArrayClassName(elementType, dim, false),
314 getArrayClassName(elementType, dim, false),
315 getDimensions(elementType, dim) + "-dimension array of "
316 + getElementTypeName(elementType));
317 if (!(elementType instanceof SimpleType ||
318 elementType instanceof CompositeType ||
319 elementType instanceof TabularType ||
320 elementType instanceof ArrayType))
321 throw new OpenDataException("The element type must be a simple " +
322 "type, an array type, a composite type " +
323 "or a tabular type.");
324 dimension = getDimensions(elementType, dim);
325 this.elementType = getElementType(elementType);
326 primitiveArray = (elementType instanceof ArrayType &&
327 ((ArrayType) elementType).isPrimitiveArray());
328 }
329
330 /**
331 * <p>
332 * Constructs a new {@link ArrayType} instance for a unidimensional
333 * array of the specified {@link SimpleType}. The attributes
334 * used by the superclass, {@link OpenType}, are automatically defined,
335 * based on these values. Both the class name and type name are set
336 * to the value returned by the {@link java.lang.Class#getName()} of
337 * the array's class. If the array is of a primitive type (indicated
338 * by giving {@code primitiveArray} the value {@code true}), the
339 * name will be '[' followed by the appropriate letter for the
340 * primitive type (see {@link java.lang.Class#getName()}). If the
341 * array is not of a primitive type, then the name is formed from
342 * the element type, preceded by '[' and an 'L', in the same way
343 * as when the multi-dimensional constructor is used.
344 * </p>
345 * <p>
346 * The description is based upon the template <code>1-dimension array
347 * of e</code>, where e is either the primitive type or a class name,
348 * depending on whether the array itself is of a primitive type or not.
349 * The class name of the actual elements is obtainable by calling
350 * {@link OpenType#getClassName()} on the result of
351 * {@link #getElementOpenType()}. This will be the appropriate wrapper
352 * class for a primitive type.
353 * </p>
354 * <p>
355 * As an example, the array type returned by
356 * <code>new ArrayType(SimpleType.INTEGER, true)</code> has the following
357 * values:
358 * </p>
359 * <table>
360 * <th><td>Attribute</td><td>Value</td></th>
361 * <tr><td>Class Name</td><td><code>[I</code>
362 * </td></tr>
363 * <tr><td>Type Name</td><td><code>[I</code>
364 * </td></tr>
365 * <tr><td>Description</td><td><code>1-dimension array of int</code></td></tr>
366 * <tr><td>Element Type Class Name</td><td><code>java.lang.Integer</code>
367 * </td></tr>
368 * </table>
369 *
370 * @param elementType the type of the elements of the array.
371 * @param primitiveArray true if the array should be of a primitive type.
372 * @throws OpenDataException if {@code primitiveArray} is {@code true},
373 * and {@link elementType} is not a valid
374 * {@link SimpleType} for a primitive type.
375 * @since 1.6
376 */
377 public ArrayType(SimpleType<?> elementType, boolean primitiveArray)
378 throws OpenDataException
379 {
380 super(getArrayClassName(elementType, 1, primitiveArray),
381 getArrayClassName(elementType, 1, primitiveArray),
382 "1-dimension array of " +
383 (primitiveArray ? getPrimitiveTypeClass(elementType).getName()
384 : elementType.getClassName()));
385 dimension = 1;
386 this.elementType = elementType;
387 this.primitiveArray = primitiveArray;
388 }
389
390 /**
391 * <p>
392 * Compares this array type with another object
393 * for equality. The objects are judged to be equal if:
394 * </p>
395 * <ul>
396 * <li><code>obj</code> is not null.</li>
397 * <li><code>obj</code> is an instance of
398 * {@link ArrayType}.</li>
399 * <li>The dimensions are equal.</li>
400 * <li>The element types are equal.</li>
401 * <li>The primitive array flag is set the same in both
402 * instances.</li>
403 * </ul>
404 *
405 * @param obj the object to compare with.
406 * @return true if the conditions above hold.
407 */
408 public boolean equals(Object obj)
409 {
410 if (!(obj instanceof ArrayType))
411 return false;
412 ArrayType atype = (ArrayType) obj;
413 return (atype.getDimension() == dimension &&
414 atype.getElementOpenType().equals(elementType) &&
415 atype.isPrimitiveArray() == primitiveArray);
416 }
417
418 /**
419 * <p>
420 * Returns a new {@link ArrayType} instance in a type-safe
421 * manner, by ensuring that the type of the given {@link OpenType}
422 * matches the component type used in the type of the
423 * returned instance. If the given {@link OpenType} is a
424 * {@link SimpleType}, {@link CompositeType} or
425 * {@link TabularType}, then a 1-dimensional array of that
426 * type is returned. Otherwise, if the type is
427 * an {@link ArrayType} of n dimensions, the returned
428 * type is also an {@link ArrayType} but of n+1 dimensions.
429 * For example,
430 * {@code ArrayType.getArrayType(ArrayType.getArrayType(SimpleType.STRING))}
431 * returns a 2-dimensional array of {@link SimpleType#String}.
432 * </p>
433 * <p>
434 * This method caches its results, so that the same instance
435 * is returned from subsequent calls with the same parameters.
436 * </p>
437 *
438 * @param elementType the element type of the new array type.
439 * @throws OpenDataException if the class name of {@code elementType}
440 * is not in {@link OpenType#ALLOWED_CLASSNAMES_LIST}.
441 * @since 1.6
442 */
443 public static <E> ArrayType<E[]> getArrayType(OpenType<E> elementType)
444 throws OpenDataException
445 {
446 ArrayType<E[]> arr = (ArrayType<E[]>) cache.get(elementType);
447 if (arr != null)
448 return arr;
449 arr = new ArrayType(1, elementType);
450 cache.put(elementType, arr);
451 return arr;
452 }
453
454 /**
455 * <p>
456 * Returns a new {@link ArrayType} instance for the given
457 * primitive type in a type-safe* manner, by ensuring that
458 * the type of the given {@link OpenType} matches the type
459 * used in the returned instance. If the type is
460 * an array of n dimensions, the returned
461 * type is also an {@link ArrayType} of n dimensions.
462 * </p>
463 * <p>
464 * As an example, the array type returned by
465 * <code>getPrimitiveArrayType(Integer.TYPE)</code> has the
466 * following values:
467 * </p>
468 * <table>
469 * <th><td>Attribute</td><td>Value</td></th>
470 * <tr><td>Class Name</td><td><code>[I</code>
471 * </td></tr>
472 * <tr><td>Type Name</td><td><code>[I</code>
473 * </td></tr>
474 * <tr><td>Description</td><td><code>1-dimension array of int</code></td></tr>
475 * <tr><td>Element Type Class Name</td><td><code>java.lang.Integer</code>
476 * </td></tr>
477 * </table>
478 * <p>
479 * This method caches its results, so that the same instance
480 * is returned from subsequent calls with the same parameters.
481 * </p>
482 *
483 * @param type the type of the new {@link ArrayType}.
484 * @throws IllegalArgumentException if the type is not a primitive
485 * array.
486 * @since 1.6
487 */
488 public static <T> ArrayType<T> getPrimitiveArrayType(Class<T> type)
489 {
490 ArrayType<T> arr = (ArrayType<T>) primCache.get(type);
491 if (arr != null)
492 return arr;
493 Class<?> comType = type;
494 int dim = 0;
495 do
496 {
497 comType = comType.getComponentType();
498 ++dim;
499 if (comType == null)
500 throw new IllegalArgumentException("The given class is " +
501 "not an array.");
502 } while (comType.isArray());
503 String className = type.getName();
504 try
505 {
506 arr = new ArrayType(getPrimitiveType(comType), true);
507 }
508 catch (OpenDataException e)
509 {
510 throw new IllegalArgumentException("The array is not of a primitive " +
511 "type", e);
512 }
513 while (dim > 1)
514 try
515 {
516 arr = new ArrayType(1, arr);
517 --dim;
518 }
519 catch (OpenDataException e)
520 {
521 throw (Error)
522 new InternalError("Couldn't generate extra dimensions").initCause(e);
523 }
524 primCache.put(type, arr);
525 return arr;
526 }
527
528 /**
529 * Returns the number of dimensions used by arrays
530 * of this type.
531 *
532 * @return the number of dimensions.
533 */
534 public int getDimension()
535 {
536 return dimension;
537 }
538
539 /**
540 * Returns the open type descriptor which describes
541 * the type of the elements of this array type.
542 *
543 * @return the type of the elements.
544 */
545 public OpenType<?> getElementOpenType()
546 {
547 return elementType;
548 }
549
550 /**
551 * <p>
552 * Returns the hash code of the array type.
553 * This is computed as the sum of the hash code of the
554 * element type together with the number of dimensions
555 * the array has and the primitive array flag. These
556 * are the same elements of the type that are compared as
557 * part of the {@link #equals(java.lang.Object)} method,
558 * thus ensuring that the hashcode is compatible with the
559 * equality test.
560 * </p>
561 * <p>
562 * As instances of this class are immutable, the hash code
563 * is computed just once for each instance and reused
564 * throughout its life.
565 * </p>
566 *
567 * @return the hash code of this instance.
568 */
569 public int hashCode()
570 {
571 if (hashCode == null)
572 hashCode = Integer.valueOf(dimension +
573 elementType.hashCode() +
574 Boolean.valueOf(primitiveArray).hashCode());
575 return hashCode.intValue();
576 }
577
578 /**
579 * Returns true if this instance represents an array of
580 * a primitive type.
581 *
582 * @return true if the array is of a primitive type.
583 */
584 public boolean isPrimitiveArray()
585 {
586 return primitiveArray;
587 }
588
589 /**
590 * <p>
591 * Returns true if the specified object is a member of this
592 * array type. The object is judged to be so if it is
593 * non-null, an array and one of the following two conditions
594 * holds:
595 * </p>
596 * <ul>
597 * <li>This {@link ArrayType} instance has a {@link SimpleType}
598 * as its element type. Thus, the object must have the same
599 * class name as that returned by {@link SimpleType#getClassName()}
600 * for this class.</li>
601 * <li>This {@link ArrayType} instance has a {@link CompositeType}
602 * or a {@link TabularType} as its element type. Thus, the object
603 * must be assignable to such an array, and have elements which
604 * are either null or valid values for the element type.</li>
605 * </ul>
606 *
607 * @param obj the object to test for membership.
608 * @return true if the object is a member of this type.
609 */
610 public boolean isValue(Object obj)
611 {
612 if (obj == null)
613 return false;
614 Class objClass = obj.getClass();
615 if (!(objClass.isArray()))
616 return false;
617 if (elementType instanceof SimpleType)
618 return getClassName().equals(objClass.getName());
619 Class elementClass = null;
620 try
621 {
622 elementClass = Class.forName(getClassName());
623 }
624 catch (ClassNotFoundException e)
625 {
626 throw new IllegalStateException("The array type's element " +
627 "class could not be found.", e);
628 }
629 if (!(elementClass.isAssignableFrom(objClass)))
630 return false;
631 for (int a = 0; a < Array.getLength(obj); ++a)
632 {
633 Object elem = Array.get(obj, a);
634 if (elem != null &&
635 (!(elementType.isValue(elem))))
636 return false;
637 }
638 return true;
639 }
640
641 /**
642 * <p>
643 * Returns a textual representation of this instance. This
644 * is constructed using the class name
645 * (<code>javax.management.openmbean.ArrayType</code>)
646 * and each element of the instance which is relevant to
647 * the definition of {@link equals(java.lang.Object)} and
648 * {@link hashCode()} (i.e. the type name, the number of
649 * dimensions and the element type).
650 * </p>
651 * <p>
652 * As instances of this class are immutable, the return value
653 * is computed just once for each instance and reused
654 * throughout its life.
655 * </p>
656 *
657 * @return a @link{java.lang.String} instance representing
658 * the instance in textual form.
659 */
660 public String toString()
661 {
662 if (string == null)
663 string = getClass().getName()
664 + "[name=" + getTypeName()
665 + ", dimension=" + dimension
666 + ", elementType=" + elementType
667 + ", primitiveArray=" + primitiveArray
668 + "]";
669 return string;
670 }
671
672 }