    View Javadoc
    1   package org.apache.bcel.classfile;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
    29   *    "Apache BCEL" must not be used to endorse or promote products
    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    "Apache BCEL", nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    48   * SUCH DAMAGE.
    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56
    57  import  org.apache.bcel.Constants;
    58  import  java.io.*;
    59
    60  /***
    61   * Abstract superclass for classes to represent the different constant types
    62   * in the constant pool of a class file. The classes keep closely to
    63   * the JVM specification.
    64   *
    65   * @version $Id: Constant.java,v 1.3 2002/07/11 19:39:04 mdahm Exp $
    66   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
    67   */
    68  public abstract class Constant implements Cloneable, Node, Serializable {
    69    /* In fact this tag is redundant since we can distinguish different
    70     * `Constant' objects by their type, i.e., via `instanceof'. In some
    71     * places we will use the tag for switch()es anyway.
    72     *
    73     * First, we want match the specification as closely as possible. Second we
    74     * need the tag as an index to select the corresponding class name from the
    75     * `CONSTANT_NAMES' array.
    76     */
    77    protected byte tag;
    78
    79    Constant(byte tag) { this.tag = tag; }
    80
    81    /***
    82     * Called by objects that are traversing the nodes of the tree implicitely
    83     * defined by the contents of a Java class. I.e., the hierarchy of methods,
    84     * fields, attributes, etc. spawns a tree of objects.
    85     *
    86     * @param v Visitor object
    87     */
    88    public abstract void accept(Visitor v);
    89
    90    public abstract void dump(DataOutputStream file) throws IOException;
    91
    92    /***
    93     * @return Tag of constant, i.e., its type. No setTag() method to avoid
    94     * confusion.
    95     */
    96    public final byte getTag() { return tag; }
    97
    98    /***
    99     * @return String representation.
    100    */
    101   public String toString() {
    102     return Constants.CONSTANT_NAMES[tag] + "[" + tag + "]";
    103   }
    104
    105   /***
    106    * @return deep copy of this constant
    107    */
    108   public Constant copy() {
    109     try {
    110       return (Constant)super.clone();
    111     } catch(CloneNotSupportedException e) {}
    112
    113     return null;
    114   }
    115
    116   public Object clone() throws CloneNotSupportedException {
    117     return super.clone();
    118   }
    119
    120   /***
    121    * Read one constant from the given file, the type depends on a tag byte.
    122    *
    123    * @param file Input stream
    124    * @return Constant object
    125    */
    126   static final Constant readConstant(DataInputStream file)
    127     throws IOException, ClassFormatException
    128   {
    129     byte b = file.readByte(); // Read tag byte
    130
    131     switch(b) {
    132     case Constants.CONSTANT_Class:              return new ConstantClass(file);
    133     case Constants.CONSTANT_Fieldref:           return new ConstantFieldref(file);
    134     case Constants.CONSTANT_Methodref:          return new ConstantMethodref(file);
    135     case Constants.CONSTANT_InterfaceMethodref: return new
    136 					ConstantInterfaceMethodref(file);
    137     case Constants.CONSTANT_String:             return new ConstantString(file);
    138     case Constants.CONSTANT_Integer:            return new ConstantInteger(file);
    139     case Constants.CONSTANT_Float:              return new ConstantFloat(file);
    140     case Constants.CONSTANT_Long:               return new ConstantLong(file);
    141     case Constants.CONSTANT_Double:             return new ConstantDouble(file);
    142     case Constants.CONSTANT_NameAndType:        return new ConstantNameAndType(file);
    143     case Constants.CONSTANT_Utf8:               return new ConstantUtf8(file);
    144     default:
    145       throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
    146     }
    147   }
    148 }

This page was automatically generated by Maven