constantclass.java

该开源工具主要用于class文件的操作

package org.apache.bcel.classfile;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import  org.apache.bcel.Constants;
import  java.io.*;

/** 
 * This class is derived from the abstract 
 * <A HREF="org.apache.bcel.classfile.Constant.html">Constant</A> class 
 * and represents a reference to a (external) class.
 *
 * @version $Id: ConstantClass.java,v 1.1.1.1 2001/10/29 19:59:58 jvanzyl Exp $
 * @author  <A HREF="mailto:[e-mail]">M. Dahm</A>
 * @see     Constant
 */
public final class ConstantClass extends Constant implements ConstantObject {
  private int name_index; // Identical to ConstantString except for the name

  /**
   * Initialize from another object.
   */
  public ConstantClass(ConstantClass c) {
    this(c.getNameIndex());
  }    

  /**
   * Initialize instance from file data.
   *
   * @param file Input stream
   * @throw IOException
   */
  ConstantClass(DataInputStream file) throws IOException
  {    
    this(file.readUnsignedShort());
  }    

  /**
   * @param name_index Name index in constant pool
   */
  public ConstantClass(int name_index) {
    super(Constants.CONSTANT_Class);
    this.name_index = name_index;
  }    

  /**
   * Called by objects that are traversing the nodes of the tree implicitely
   * defined by the contents of a Java class. I.e., the hierarchy of methods,
   * fields, attributes, etc. spawns a tree of objects.
   *
   * @param v Visitor object
   */
  public void accept(Visitor v) {
    v.visitConstantClass(this);
  }    

  /** 
   * Dump constant class to file stream in binary format.
   *
   * @param file Output file stream
   * @throw IOException
   */ 
  public final void dump(DataOutputStream file) throws IOException
  {
    file.writeByte(tag);
    file.writeShort(name_index);
  }    

  /**
   * @return Name index in constant pool of class name.
   */  
  public final int getNameIndex() { return name_index; }    

  /**
   * @param name_index.
   */
  public final void setNameIndex(int name_index) {
    this.name_index = name_index;
  }    


  /** @return String object
   */
  public Object getConstantValue(ConstantPool cp) {
    Constant c = cp.getConstant(name_index, Constants.CONSTANT_Utf8);
    return ((ConstantUtf8)c).getBytes();
  }

  /** @return dereferenced string
   */
  public String getBytes(ConstantPool cp) {
    return (String)getConstantValue(cp);
  }

  /**
   * @return String representation.
   */
  public final String toString() {
    return super.toString() + "(name_index = " + name_index + ")";
  }
}