libjava/classpath/vm/reference/java/lang/reflect/Constructor.java

   1 /* java.lang.reflect.Constructor - reflection of Java constructors
   2    Copyright (C) 1998, 2001 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.lang.reflect;
  40
  41 import java.util.Arrays;
  42
  43 /**
  44  * The Constructor class represents a constructor of a class. It also allows
  45  * dynamic creation of an object, via reflection. Invocation on Constructor
  46  * objects knows how to do widening conversions, but throws
  47  * {@link IllegalArgumentException} if a narrowing conversion would be
  48  * necessary. You can query for information on this Constructor regardless
  49  * of location, but construction access may be limited by Java language
  50  * access controls. If you can't do it in the compiler, you can't normally
  51  * do it here either.<p>
  52  *
  53  * <B>Note:</B> This class returns and accepts types as Classes, even
  54  * primitive types; there are Class types defined that represent each
  55  * different primitive type.  They are <code>java.lang.Boolean.TYPE,
  56  * java.lang.Byte.TYPE,</code>, also available as <code>boolean.class,
  57  * byte.class</code>, etc.  These are not to be confused with the
  58  * classes <code>java.lang.Boolean, java.lang.Byte</code>, etc., which are
  59  * real classes.<p>
  60  *
  61  * Also note that this is not a serializable class.  It is entirely feasible
  62  * to make it serializable using the Externalizable interface, but this is
  63  * on Sun, not me.
  64  *
  65  * @author John Keiser
  66  * @author Eric Blake <ebb9@email.byu.edu>
  67  * @see Member
  68  * @see Class
  69  * @see java.lang.Class#getConstructor(Class[])
  70  * @see java.lang.Class#getDeclaredConstructor(Class[])
  71  * @see java.lang.Class#getConstructors()
  72  * @see java.lang.Class#getDeclaredConstructors()
  73  * @since 1.1
  74  * @status updated to 1.4
  75  */
  76 public final class Constructor
  77 extends AccessibleObject implements Member
  78 {
  79   private Class clazz;
  80   private int slot;
  81
  82   /**
  83    * This class is uninstantiable except from native code.
  84    */
  85   private Constructor(Class declaringClass,int slot)
  86   {
  87     this.clazz = declaringClass;
  88     this.slot = slot;
  89   }
  90
  91   private Constructor()
  92   {
  93   }
  94
  95   /**
  96    * Gets the class that declared this constructor.
  97    * @return the class that declared this member
  98    */
  99   public Class getDeclaringClass()
 100   {
 101     return clazz;
 102   }
 103
 104   /**
 105    * Gets the name of this constructor (the non-qualified name of the class
 106    * it was declared in).
 107    * @return the name of this constructor
 108    */
 109   public String getName()
 110   {
 111     return getDeclaringClass().getName();
 112   }
 113
 114   /**
 115    * Gets the modifiers this constructor uses.  Use the <code>Modifier</code>
 116    * class to interpret the values. A constructor can only have a subset of the
 117    * following modifiers: public, private, protected.
 118    *
 119    * @return an integer representing the modifiers to this Member
 120    * @see Modifier
 121    */
 122   public native int getModifiers();
 123
 124   /**
 125    * Get the parameter list for this constructor, in declaration order. If the
 126    * constructor takes no parameters, returns a 0-length array (not null).
 127    *
 128    * @return a list of the types of the constructor's parameters
 129    */
 130   public native Class[] getParameterTypes();
 131
 132   /**
 133    * Get the exception types this constructor says it throws, in no particular
 134    * order. If the constructor has no throws clause, returns a 0-length array
 135    * (not null).
 136    *
 137    * @return a list of the types in the constructor's throws clause
 138    */
 139   public native Class[] getExceptionTypes();
 140
 141   /**
 142    * Compare two objects to see if they are semantically equivalent.
 143    * Two Constructors are semantically equivalent if they have the same
 144    * declaring class and the same parameter list.  This ignores different
 145    * exception clauses, but since you can't create a Method except through the
 146    * VM, this is just the == relation.
 147    *
 148    * @param o the object to compare to
 149    * @return <code>true</code> if they are equal; <code>false</code> if not.
 150    */
 151   public boolean equals(Object o)
 152   {
 153     if (!(o instanceof Constructor))
 154       return false;
 155     Constructor that = (Constructor)o;
 156     if (this.getDeclaringClass() != that.getDeclaringClass())
 157       return false;
 158     if (!Arrays.equals(this.getParameterTypes(), that.getParameterTypes()))
 159       return false;
 160     return true;
 161   }
 162
 163   /**
 164    * Get the hash code for the Constructor. The Constructor hash code is the
 165    * hash code of the declaring class's name.
 166    *
 167    * @return the hash code for the object
 168    */
 169   public int hashCode()
 170   {
 171     return getDeclaringClass().getName().hashCode();
 172   }
 173
 174   /**
 175    * Get a String representation of the Constructor. A Constructor's String
 176    * representation is "&lt;modifier&gt; &lt;classname&gt;(&lt;paramtypes&gt;)
 177    * throws &lt;exceptions&gt;", where everything after ')' is omitted if
 178    * there are no exceptions.<br> Example:
 179    * <code>public java.io.FileInputStream(java.lang.Runnable)
 180    * throws java.io.FileNotFoundException</code>
 181    *
 182    * @return the String representation of the Constructor
 183    */
 184   public String toString()
 185   {
 186     // 128 is a reasonable buffer initial size for constructor
 187     StringBuffer sb = new StringBuffer(128);
 188     Modifier.toString(getModifiers(), sb).append(' ');
 189     sb.append(getDeclaringClass().getName()).append('(');
 190     Class[] c = getParameterTypes();
 191     if (c.length > 0)
 192       {
 193         sb.append(c[0].getName());
 194         for (int i = 1; i < c.length; i++)
 195           sb.append(',').append(c[i].getName());
 196       }
 197     sb.append(')');
 198     c = getExceptionTypes();
 199     if (c.length > 0)
 200       {
 201         sb.append(" throws ").append(c[0].getName());
 202         for (int i = 1; i < c.length; i++)
 203           sb.append(',').append(c[i].getName());
 204       }
 205     return sb.toString();
 206   }
 207
 208   /**
 209    * Create a new instance by invoking the constructor. Arguments are
 210    * automatically unwrapped and widened, if needed.<p>
 211    *
 212    * If this class is abstract, you will get an
 213    * <code>InstantiationException</code>. If the constructor takes 0
 214    * arguments, you may use null or a 0-length array for <code>args</code>.<p>
 215    *
 216    * If this Constructor enforces access control, your runtime context is
 217    * evaluated, and you may have an <code>IllegalAccessException</code> if
 218    * you could not create this object in similar compiled code. If the class
 219    * is uninitialized, you trigger class initialization, which may end in a
 220    * <code>ExceptionInInitializerError</code>.<p>
 221    *
 222    * Then, the constructor is invoked. If it completes normally, the return
 223    * value will be the new object. If it completes abruptly, the exception is
 224    * wrapped in an <code>InvocationTargetException</code>.
 225    *
 226    * @param args the arguments to the constructor
 227    * @return the newly created object
 228    * @throws IllegalAccessException if the constructor could not normally be
 229    *         called by the Java code (i.e. it is not public)
 230    * @throws IllegalArgumentException if the number of arguments is incorrect;
 231    *         or if the arguments types are wrong even with a widening
 232    *         conversion
 233    * @throws InstantiationException if the class is abstract
 234    * @throws InvocationTargetException if the constructor throws an exception
 235    * @throws ExceptionInInitializerError if construction triggered class
 236    *         initialization, which then failed
 237    */
 238   public Object newInstance(Object args[])
 239     throws InstantiationException, IllegalAccessException,
 240            InvocationTargetException
 241   {
 242     return constructNative(args, clazz, slot);
 243   }
 244
 245   private native Object constructNative(Object[] args, Class declaringClass,
 246                                         int slot)
 247     throws InstantiationException, IllegalAccessException,
 248            InvocationTargetException;
 249 }