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.HashMap;
043    import java.util.Map;
044    
045    /**
046     * The open type descriptor for arrays of open data values.
047     *
048     * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
049     * @since 1.5
050     */
051    public class ArrayType<T>
052      extends OpenType<T>
053    {
054    
055      /**
056       * Compatible with JDK 1.5
057       */
058      private static final long serialVersionUID = 720504429830309770L;
059    
060      /**
061       * The number of dimensions arrays of this type has.
062       */
063      private int dimension;
064    
065      /**
066       * The element type of arrays of this type.
067       */
068      private OpenType<?> elementType;
069    
070      /**
071       * True if this type represents a primitive array.
072       */
073      private boolean primitiveArray;
074    
075      /**
076       * The hash code of this instance.
077       */
078      private transient Integer hashCode;
079    
080      /**
081       * The <code>toString()</code> result of this instance.
082       */
083      private transient String string;
084    
085      /**
086       * A cache of {@link ArrayType} instances created
087       * by {@link #getArrayType(OpenType)}.
088       */
089      private static final Map<OpenType<?>,ArrayType<?>> cache =
090        new HashMap<OpenType<?>,ArrayType<?>>();
091    
092      /**
093       * A cache of {@link ArrayType} instances created
094       * by {@link #getPrimitiveArrayType(Class)}.
095       */
096      private static final Map<Class<?>,ArrayType<?>> primCache =
097        new HashMap<Class<?>,ArrayType<?>>();
098    
099      /**
100       * Returns the class name of the array, given the element
101       * class name and its dimensions.
102       *
103       * @param elementType the type of the array's elements.
104       * @param dim the dimensions of the array.
105       * @param primitive true if this should be a primitive array.
106       * @return the array's class name.
107       * @throws OpenDataException if the class name does not reference
108       *                           a loadable class.
109       */
110      private static final String getArrayClassName(OpenType<?> elementType,
111                                                    int dim,
112                                                    boolean primitive)
113        throws OpenDataException
114      {
115        Class<?> type;
116        if (primitive)
117          type = getPrimitiveTypeClass((SimpleType<?>) elementType);
118        else
119          {
120            String className = elementType.getClassName();
121            try
122              {
123                type = Class.forName(className);
124              }
125            catch (ClassNotFoundException e)
126              {
127                throw new OpenDataException("The class name, " + className +
128                                            ", is unavailable.");
129              }
130          }
131        while (type.isArray())
132          type = type.getComponentType();
133        return
134          Array.newInstance(type,
135                            new int[getDimensions(elementType, dim)]).getClass().getName();
136      }
137    
138      /**
139       * Returns the dimensions of the new {@link ArrayType},
140       * based on whether the given element type is already an
141       * {@link ArrayType} or not.
142       *
143       * @param elementType the type of the array.
144       * @param dim the proposed dimensions.
145       * @return the resultant dimensions.
146       * @throws IllegalArgumentException if <code>dim</code> is less than 1.
147       */
148      private static final int getDimensions(OpenType<?> elementType,
149                                             int dim)
150      {
151        if (dim < 1)
152          throw new IllegalArgumentException("Dimensions must be greater " +
153                                             "than or equal to 1.");
154        if (elementType instanceof ArrayType)
155          return dim + ((ArrayType<?>) elementType).getDimension();
156        return dim;
157      }
158    
159      /**
160       * Returns the appropriate primitive type name, given the
161       * corresponding wrapper class.
162       *
163       * @param type the type to convert.
164       * @return the corresponding primitive type.
165       * @throws OpenDataException if {@code type} is not a valid
166       *                           {@link Class} for a primitive type.
167       *
168       */
169      private static final SimpleType<?> getPrimitiveType(Class<?> type)
170        throws OpenDataException
171      {
172        if (type.equals(Boolean.TYPE))
173          return SimpleType.BOOLEAN;
174        if (type.equals(Byte.TYPE))
175          return SimpleType.BYTE;
176        if (type.equals(Character.TYPE))
177          return SimpleType.CHARACTER;
178        if (type.equals(Double.TYPE))
179          return SimpleType.DOUBLE;
180        if (type.equals(Float.TYPE))
181          return SimpleType.FLOAT;
182        if (type.equals(Integer.TYPE))
183          return SimpleType.INTEGER;
184        if (type.equals(Long.TYPE))
185          return SimpleType.LONG;
186        if (type.equals(Short.TYPE))
187          return SimpleType.SHORT;
188        if (type.equals(Void.TYPE))
189          return SimpleType.VOID;
190        throw new OpenDataException(type + " is not a primitive type.");
191      }
192    
193      /**
194       * Returns the appropriate primitive type name, given the
195       * corresponding wrapper class.
196       *
197       * @param type the type to convert.
198       * @return the corresponding primitive type.
199       * @throws OpenDataException if {@code type} is not a valid
200       *                           {@link SimpleType} for a primitive type.
201       *
202       */
203      private static final Class<?> getPrimitiveTypeClass(SimpleType<?> type)
204        throws OpenDataException
205      {
206        if (type.equals(SimpleType.BOOLEAN))
207          return Boolean.TYPE;
208        if (type.equals(SimpleType.BYTE))
209          return Byte.TYPE;
210        if (type.equals(SimpleType.CHARACTER))
211          return Character.TYPE;
212        if (type.equals(SimpleType.DOUBLE))
213          return Double.TYPE;
214        if (type.equals(SimpleType.FLOAT))
215          return Float.TYPE;
216        if (type.equals(SimpleType.INTEGER))
217          return Integer.TYPE;
218        if (type.equals(SimpleType.LONG))
219          return Long.TYPE;
220        if (type.equals(SimpleType.SHORT))
221          return Short.TYPE;
222        if (type.equals(SimpleType.VOID))
223          return Void.TYPE;
224        throw new OpenDataException(type + " is not a primitive type.");
225      }
226    
227      /**
228       * Returns the element type that will actually be used, if the
229       * specified element type is passed to a constructor.  This is
230       * necessary to ensure that a non-array type is still returned when
231       * an {@link ArrayType} is constructed from an {@link ArrayType}.
232       *
233       * @param elemType the element type that was supplied.
234       * @return the element type that will be used.
235       */
236      private static final OpenType<?> getElementType(OpenType<?> elemType)
237      {
238        if (elemType instanceof ArrayType)
239          return ((ArrayType<?>) elemType).getElementOpenType();
240        return elemType;
241      }
242    
243      /**
244       * Returns the element type name that will actually be used, if the
245       * specified element type is passed to a constructor.  This is
246       * necessary to ensure that a non-array type is still returned when
247       * an {@link ArrayType} is constructed from an {@link ArrayType},
248       * and that primitive arrays are described correctly.
249       *
250       * @param elemType the element type that was supplied.
251       * @return the element type name that will be used.
252       * @throws OpenDataException if the element type is not a valid
253       *                           {@link SimpleType} for a primitive type.
254       */
255      private static final String getElementTypeName(OpenType<?> elemType)
256        throws OpenDataException
257      {
258        OpenType<?> trueElemType = getElementType(elemType);
259        if (elemType instanceof ArrayType &&
260            ((ArrayType<?>) elemType).isPrimitiveArray())
261          return getPrimitiveTypeClass((SimpleType<?>) trueElemType).getName();
262        return trueElemType.getClassName();
263      }
264    
265      /**
266       * <p>
267       * Constructs a new {@link ArrayType} instance for an array of the
268       * specified type with the supplied number of dimensions.  The attributes
269       * used by the superclass, {@link OpenType}, are automatically defined,
270       * based on these values.  Both the class name and type name are set
271       * to the value returned by the {@link java.lang.Class#getName()} of
272       * the array's class (i.e. the element type, preceded by n instances of
273       * '[' and an 'L', where n is the number of dimensions the array has).
274       * The description is based upon the template <code>n-dimension array
275       * of e</code>, where n is the number of dimensions of the array, and
276       * e is the element type.  The class name of the actual elements is
277       * obtainable by calling {@link OpenType#getClassName()} on the result
278       * of {@link #getElementOpenType()}.
279       * </p>
280       * <p>
281       * As an example, the array type returned by
282       * <code>new ArrayType(6, SimpleType.INTEGER)</code> has the following
283       * values:
284       * </p>
285       * <table>
286       * <th><td>Attribute</td><td>Value</td></th>
287       * <tr><td>Class Name</td><td><code>[[[[[[Ljava.lang.Integer;</code>
288       * </td></tr>
289       * <tr><td>Type Name</td><td><code>[[[[[[Ljava.lang.Integer;</code>
290       * </td></tr>
291       * <tr><td>Description</td><td><code>6-dimension array of
292       * java.lang.Integer</code></td></tr>
293       * <tr><td>Element Type Class Name</td><td><code>java.lang.Integer</code>
294       * </td></tr>
295       * </table>
296       * <p>
297       * The dimensions of the array must be equal to or greater than 1.  The
298       * element type must be an instance of {@link SimpleType},
299       * {@link CompositeType} or {@link TabularType}.
300       * </p>
301       *
302       * @param dim the dimensions of the array.
303       * @param elementType the type of the elements of the array.
304       * @throws IllegalArgumentException if <code>dim</code> is less than 1.
305       * @throws OpenDataException if the element type is not an instance of either
306       *                           {@link SimpleType}, {@link CompositeType}
307       *                           or {@link TabularType}.
308       */
309      public ArrayType(int dim, OpenType<?> elementType)
310        throws OpenDataException
311      {
312        super(getArrayClassName(elementType, dim, false),
313              getArrayClassName(elementType, dim, false),
314              getDimensions(elementType, dim) + "-dimension array of "
315              + getElementTypeName(elementType));
316        if (!(elementType instanceof SimpleType ||
317              elementType instanceof CompositeType ||
318              elementType instanceof TabularType ||
319              elementType instanceof ArrayType))
320          throw new OpenDataException("The element type must be a simple " +
321                                      "type, an array type, a composite type " +
322                                      "or a tabular type.");
323        dimension = getDimensions(elementType, dim);
324        this.elementType = getElementType(elementType);
325        primitiveArray = (elementType instanceof ArrayType &&
326                          ((ArrayType<?>) elementType).isPrimitiveArray());
327      }
328    
329      /**
330       * <p>
331       * Constructs a new {@link ArrayType} instance for a unidimensional
332       * array of the specified {@link SimpleType}.  The attributes
333       * used by the superclass, {@link OpenType}, are automatically defined,
334       * based on these values.  Both the class name and type name are set
335       * to the value returned by the {@link java.lang.Class#getName()} of
336       * the array's class.  If the array is of a primitive type (indicated
337       * by giving {@code primitiveArray} the value {@code true}), the
338       * name will be '[' followed by the appropriate letter for the
339       * primitive type (see {@link java.lang.Class#getName()}).  If the
340       * array is not of a primitive type, then the name is formed from
341       * the element type, preceded by '[' and an 'L', in the same way
342       * as when the multi-dimensional constructor is used.
343       * </p>
344       * <p>
345       * The description is based upon the template <code>1-dimension array
346       * of e</code>, where e is either the primitive type or a class name,
347       * depending on whether the array itself is of a primitive type or not.
348       * The class name of the actual elements is obtainable by calling
349       * {@link OpenType#getClassName()} on the result of
350       * {@link #getElementOpenType()}.  This will be the appropriate wrapper
351       * class for a primitive type.
352       * </p>
353       * <p>
354       * As an example, the array type returned by
355       * <code>new ArrayType(SimpleType.INTEGER, true)</code> has the following
356       * values:
357       * </p>
358       * <table>
359       * <th><td>Attribute</td><td>Value</td></th>
360       * <tr><td>Class Name</td><td><code>[I</code>
361       * </td></tr>
362       * <tr><td>Type Name</td><td><code>[I</code>
363       * </td></tr>
364       * <tr><td>Description</td><td><code>1-dimension array of int</code></td></tr>
365       * <tr><td>Element Type Class Name</td><td><code>java.lang.Integer</code>
366       * </td></tr>
367       * </table>
368       *
369       * @param elementType the type of the elements of the array.
370       * @param primitiveArray true if the array should be of a primitive type.
371       * @throws OpenDataException if {@code primitiveArray} is {@code true},
372       *                           and {@link elementType} is not a valid
373       *                           {@link SimpleType} for a primitive type.
374       * @since 1.6
375       */
376      public ArrayType(SimpleType<?> elementType, boolean primitiveArray)
377        throws OpenDataException
378      {
379        super(getArrayClassName(elementType, 1, primitiveArray),
380              getArrayClassName(elementType, 1, primitiveArray),
381              "1-dimension array of " +
382              (primitiveArray ? getPrimitiveTypeClass(elementType).getName()
383               : elementType.getClassName()));
384        dimension = 1;
385        this.elementType = elementType;
386        this.primitiveArray = primitiveArray;
387      }
388    
389      /**
390       * <p>
391       * Compares this array type with another object
392       * for equality.  The objects are judged to be equal if:
393       * </p>
394       * <ul>
395       * <li><code>obj</code> is not null.</li>
396       * <li><code>obj</code> is an instance of
397       * {@link ArrayType}.</li>
398       * <li>The dimensions are equal.</li>
399       * <li>The element types are equal.</li>
400       * <li>The primitive array flag is set the same in both
401       * instances.</li>
402       * </ul>
403       *
404       * @param obj the object to compare with.
405       * @return true if the conditions above hold.
406       */
407      public boolean equals(Object obj)
408      {
409        if (!(obj instanceof ArrayType))
410          return false;
411        ArrayType<?> atype = (ArrayType<?>) obj;
412        return (atype.getDimension() == dimension &&
413                atype.getElementOpenType().equals(elementType) &&
414                atype.isPrimitiveArray() == primitiveArray);
415      }
416    
417      /**
418       * <p>
419       * Returns a new {@link ArrayType} instance in a type-safe
420       * manner, by ensuring that the type of the given {@link OpenType}
421       * matches the component type used in the type of the
422       * returned instance.  If the given {@link OpenType} is a
423       * {@link SimpleType}, {@link CompositeType} or
424       * {@link TabularType}, then a 1-dimensional array of that
425       * type is returned.  Otherwise, if the type is
426       * an {@link ArrayType} of n dimensions, the returned
427       * type is also an {@link ArrayType} but of n+1 dimensions.
428       * For example,
429       * {@code ArrayType.getArrayType(ArrayType.getArrayType(SimpleType.STRING))}
430       * returns a 2-dimensional array of {@link SimpleType#String}.
431       * </p>
432       * <p>
433       * This method caches its results, so that the same instance
434       * is returned from subsequent calls with the same parameters.
435       * </p>
436       *
437       * @param elementType the element type of the new array type.
438       * @throws OpenDataException if the class name of {@code elementType}
439       *                           is not in {@link OpenType#ALLOWED_CLASSNAMES_LIST}.
440       * @since 1.6
441       */
442      @SuppressWarnings("unchecked")
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<E[]>(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      @SuppressWarnings("unchecked")
489      public static <T> ArrayType<T> getPrimitiveArrayType(Class<T> type)
490      {
491        ArrayType<T> arr = (ArrayType<T>) primCache.get(type);
492        if (arr != null)
493          return arr;
494        Class<?> comType = type;
495        int dim = 0;
496        do
497          {
498            comType = comType.getComponentType();
499            ++dim;
500            if (comType == null)
501              throw new IllegalArgumentException("The given class is " +
502                                                 "not an array.");
503          } while (comType.isArray());
504        try
505          {
506            arr = new ArrayType<T>(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<T>(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    }