Java example source code file (FieldGen.java)

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Java - Java tags/keywords

arraylist, classgenexception, constantpoolgen, constantvalue, fieldgen, float, integer, long, objecttype, only, string, stringbuffer, types, unhandled, util

The FieldGen.java Java example source code

/*
 * reserved comment block
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package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================
 * 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.
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 *    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 apache@apache.org.
 *
 * 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
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 * 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 com.sun.org.apache.bcel.internal.Constants;
import com.sun.org.apache.bcel.internal.classfile.*;
import java.util.ArrayList;
import java.util.Iterator;

/**
 * Template class for building up a field.  The only extraordinary thing
 * one can do is to add a constant value attribute to a field (which must of
 * course be compatible with to the declared type).
 *
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm
 * @see Field
 */
public class FieldGen extends FieldGenOrMethodGen {
  private Object value = null;

  /**
   * Declare a field. If it is static (isStatic() == true) and has a
   * basic type like int or String it may have an initial value
   * associated with it as defined by setInitValue().
   *
   * @param access_flags access qualifiers
   * @param type  field type
   * @param name field name
   * @param cp constant pool
   */
  public FieldGen(int access_flags, Type type, String name, ConstantPoolGen cp) {
    setAccessFlags(access_flags);
    setType(type);
    setName(name);
    setConstantPool(cp);
  }

  /**
   * Instantiate from existing field.
   *
   * @param field Field object
   * @param cp constant pool (must contain the same entries as the field's constant pool)
   */
  public FieldGen(Field field, ConstantPoolGen cp) {
    this(field.getAccessFlags(), Type.getType(field.getSignature()), field.getName(), cp);

    Attribute[] attrs = field.getAttributes();

    for(int i=0; i < attrs.length; i++) {
      if(attrs[i] instanceof ConstantValue)
        setValue(((ConstantValue)attrs[i]).getConstantValueIndex());
      else
        addAttribute(attrs[i]);
    }
  }

  private void setValue(int index) {
    ConstantPool cp  = this.cp.getConstantPool();
    Constant     c   = cp.getConstant(index);
    value = ((ConstantObject)c).getConstantValue(cp);
  }

  /**
   * Set (optional) initial value of field, otherwise it will be set to null/0/false
   * by the JVM automatically.
   */
  public void setInitValue(String str) {
    checkType(new ObjectType("java.lang.String"));

    if(str != null)
      value = str;
  }

  public void setInitValue(long l) {
    checkType(Type.LONG);

    if(l != 0L)
      value = new Long(l);
  }

  public void setInitValue(int i) {
    checkType(Type.INT);

    if(i != 0)
      value = new Integer(i);
  }

  public void setInitValue(short s) {
    checkType(Type.SHORT);

    if(s != 0)
      value = new Integer(s);
  }

  public void setInitValue(char c) {
    checkType(Type.CHAR);

    if(c != 0)
      value = new Integer(c);
  }

  public void setInitValue(byte b) {
    checkType(Type.BYTE);

    if(b != 0)
      value = new Integer(b);
  }

  public void setInitValue(boolean b) {
    checkType(Type.BOOLEAN);

    if(b)
      value = new Integer(1);
  }

  public void setInitValue(float f) {
    checkType(Type.FLOAT);

    if(f != 0.0)
      value = new Float(f);
  }

  public void setInitValue(double d) {
    checkType(Type.DOUBLE);

    if(d != 0.0)
      value = new Double(d);
  }

  /** Remove any initial value.
   */
  public void cancelInitValue() {
    value = null;
  }

  private void checkType(Type atype) {
    if(type == null)
      throw new ClassGenException("You haven't defined the type of the field yet");

    if(!isFinal())
      throw new ClassGenException("Only final fields may have an initial value!");

    if(!type.equals(atype))
      throw new ClassGenException("Types are not compatible: " + type + " vs. " + atype);
  }

  /**
   * Get field object after having set up all necessary values.
   */
  public Field getField() {
    String      signature       = getSignature();
    int         name_index      = cp.addUtf8(name);
    int         signature_index = cp.addUtf8(signature);

    if(value != null) {
      checkType(type);
      int index = addConstant();
      addAttribute(new ConstantValue(cp.addUtf8("ConstantValue"),
                                     2, index, cp.getConstantPool()));
    }

    return new Field(access_flags, name_index, signature_index, getAttributes(),
                     cp.getConstantPool());
  }

  private int addConstant() {
    switch(type.getType()) {
    case Constants.T_INT: case Constants.T_CHAR: case Constants.T_BYTE:
    case Constants.T_BOOLEAN: case Constants.T_SHORT:
      return cp.addInteger(((Integer)value).intValue());

    case Constants.T_FLOAT:
      return cp.addFloat(((Float)value).floatValue());

    case Constants.T_DOUBLE:
      return cp.addDouble(((Double)value).doubleValue());

    case Constants.T_LONG:
      return cp.addLong(((Long)value).longValue());

    case Constants.T_REFERENCE:
      return cp.addString(((String)value));

    default:
      throw new RuntimeException("Oops: Unhandled : " + type.getType());
    }
  }

  public String  getSignature()  { return type.getSignature(); }

  private ArrayList observers;

  /** Add observer for this object.
   */
  public void addObserver(FieldObserver o) {
    if(observers == null)
      observers = new ArrayList();

    observers.add(o);
  }

  /** Remove observer for this object.
   */
  public void removeObserver(FieldObserver o) {
    if(observers != null)
      observers.remove(o);
  }

  /** Call notify() method on all observers. This method is not called
   * automatically whenever the state has changed, but has to be
   * called by the user after he has finished editing the object.
   */
  public void update() {
    if(observers != null)
      for(Iterator e = observers.iterator(); e.hasNext(); )
        ((FieldObserver)e.next()).notify(this);
  }

  public String getInitValue() {
    if(value != null) {
      return value.toString();
    } else
      return null;
  }

  /**
   * Return string representation close to declaration format,
   * `public static final short MAX = 100', e.g..
   *
   * @return String representation of field
   */
  public final String toString() {
    String name, signature, access; // Short cuts to constant pool

    access    = Utility.accessToString(access_flags);
    access    = access.equals("")? "" : (access + " ");
    signature = type.toString();
    name      = getName();

    StringBuffer buf = new StringBuffer(access + signature + " " + name);
    String value = getInitValue();

    if(value != null)
      buf.append(" = " + value);

    return buf.toString();
  }

  /** @return deep copy of this field
   */
  public FieldGen copy(ConstantPoolGen cp) {
    FieldGen fg = (FieldGen)clone();

    fg.setConstantPool(cp);
    return fg;
  }
}