expression.java

java1.6众多例子参考

   *
   * @param xctxt The XPath runtime context.
   * NEEDSDOC @param handler
   *
   * @return The result of the expression in the form of a <code>XObject</code>.
   *
   * @throws javax.xml.transform.TransformerException if a runtime exception
   *         occurs.
   * @throws org.xml.sax.SAXException
   */
  public void executeCharsToContentHandler(
          XPathContext xctxt, ContentHandler handler)
            throws javax.xml.transform.TransformerException,
                   org.xml.sax.SAXException
  {

    XObject obj = execute(xctxt);

    obj.dispatchCharactersEvents(handler);
    obj.detach();
  }

  /**
   * Tell if this expression returns a stable number that will not change during 
   * iterations within the expression.  This is used to determine if a proximity 
   * position predicate can indicate that no more searching has to occur.
   * 
   *
   * @return true if the expression represents a stable number.
   */
  public boolean isStableNumber()
  {
    return false;
  }

  /**
   * This function is used to fixup variables from QNames to stack frame
   * indexes at stylesheet build time.
   * @param vars List of QNames that correspond to variables.  This list
   * should be searched backwards for the first qualified name that
   * corresponds to the variable reference qname.  The position of the
   * QName in the vector from the start of the vector will be its position
   * in the stack frame (but variables above the globalsTop value will need
   * to be offset to the current stack frame).
   * NEEDSDOC @param globalsSize
   */
  public abstract void fixupVariables(java.util.Vector vars, int globalsSize);
  
  /**
   * Compare this object with another object and see 
   * if they are equal, include the sub heararchy.
   * 
   * @param expr Another expression object.
   * @return true if this objects class and the expr
   * object's class are the same, and the data contained 
   * within both objects are considered equal.
   */
  public abstract boolean deepEquals(Expression expr);
  
  /**
   * This is a utility method to tell if the passed in 
   * class is the same class as this.  It is to be used by
   * the deepEquals method.  I'm bottlenecking it here 
   * because I'm not totally confident that comparing the 
   * class objects is the best way to do this.
   * @return true of the passed in class is the exact same 
   * class as this class.
   */
  protected final boolean isSameClass(Expression expr)
  {
  	if(null == expr)
  	  return false;
  	  
  	return (getClass() == expr.getClass());
  }

  /**
   * Warn the user of an problem.
   *
   * @param xctxt The XPath runtime context.
   * @param msg An error msgkey that corresponds to one of the conststants found
   *            in {@link com.sun.org.apache.xpath.internal.res.XPATHErrorResources}, which is
   *            a key for a format string.
   * @param args An array of arguments represented in the format string, which
   *             may be null.
   *
   * @throws TransformerException if the current ErrorListoner determines to
   *                              throw an exception.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public void warn(XPathContext xctxt, String msg, Object[] args)
          throws javax.xml.transform.TransformerException
  {

    java.lang.String fmsg = XSLMessages.createXPATHWarning(msg, args);

    if (null != xctxt)
    {
      ErrorListener eh = xctxt.getErrorListener();

      // TO DO: Need to get stylesheet Locator from here.
      eh.warning(new TransformerException(fmsg, xctxt.getSAXLocator()));
    }
  }

  /**
   * Tell the user of an assertion error, and probably throw an
   * exception.
   *
   * @param b  If false, a runtime exception will be thrown.
   * @param msg The assertion message, which should be informative.
   *
   * @throws RuntimeException if the b argument is false.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public void assertion(boolean b, java.lang.String msg)
  {

    if (!b)
    {
      java.lang.String fMsg = XSLMessages.createXPATHMessage(
        XPATHErrorResources.ER_INCORRECT_PROGRAMMER_ASSERTION,
        new Object[]{ msg });

      throw new RuntimeException(fMsg);
    }
  }

  /**
   * Tell the user of an error, and probably throw an
   * exception.
   *
   * @param xctxt The XPath runtime context.
   * @param msg An error msgkey that corresponds to one of the constants found
   *            in {@link com.sun.org.apache.xpath.internal.res.XPATHErrorResources}, which is
   *            a key for a format string.
   * @param args An array of arguments represented in the format string, which
   *             may be null.
   *
   * @throws TransformerException if the current ErrorListoner determines to
   *                              throw an exception.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public void error(XPathContext xctxt, String msg, Object[] args)
          throws javax.xml.transform.TransformerException
  {

    java.lang.String fmsg = XSLMessages.createXPATHMessage(msg, args);

    if (null != xctxt)
    {
      ErrorListener eh = xctxt.getErrorListener();
      TransformerException te = new TransformerException(fmsg, this);

      eh.fatalError(te);
    }
  }
  
  /**
   * Get the first non-Expression parent of this node.
   * @return null or first ancestor that is not an Expression.
   */
  public ExpressionNode getExpressionOwner()
  {
  	ExpressionNode parent = exprGetParent();
  	while((null != parent) && (parent instanceof Expression))
  		parent = parent.exprGetParent();
  	return parent;
  }
  
  //=============== ExpressionNode methods ================
  
  /** This pair of methods are used to inform the node of its
    parent. */
  public void exprSetParent(ExpressionNode n)
  {
  	assertion(n != this, "Can not parent an expression to itself!");
  	m_parent = n;
  }
  
  public ExpressionNode exprGetParent()
  {
  	return m_parent;
  }

  /** This method tells the node to add its argument to the node's
    list of children.  */
  public void exprAddChild(ExpressionNode n, int i)
  {
  	assertion(false, "exprAddChild method not implemented!");
  }

  /** This method returns a child node.  The children are numbered
     from zero, left to right. */
  public ExpressionNode exprGetChild(int i)
  {
  	return null;
  }

  /** Return the number of children the node has. */
  public int exprGetNumChildren()
  {
  	return 0;
  }
  
  //=============== SourceLocator methods ================

  /**
   * Return the public identifier for the current document event.
   *
   * <p>The return value is the public identifier of the document
   * entity or of the external parsed entity in which the markup that
   * triggered the event appears.</p>
   *
   * @return A string containing the public identifier, or
   *         null if none is available.
   * @see #getSystemId
   */
  public String getPublicId()
  {
  	if(null == m_parent)
  	  return null;
  	return m_parent.getPublicId();
  }

  /**
   * Return the system identifier for the current document event.
   *
   * <p>The return value is the system identifier of the document
   * entity or of the external parsed entity in which the markup that
   * triggered the event appears.</p>
   *
   * <p>If the system identifier is a URL, the parser must resolve it
   * fully before passing it to the application.</p>
   *
   * @return A string containing the system identifier, or null
   *         if none is available.
   * @see #getPublicId
   */
  public String getSystemId()
  {
  	if(null == m_parent)
  	  return null;
  	return m_parent.getSystemId();
  }

  /**
   * Return the line number where the current document event ends.
   *
   * <p><strong>Warning:</strong> The return value from the method
   * is intended only as an approximation for the sake of error
   * reporting; it is not intended to provide sufficient information
   * to edit the character content of the original XML document.</p>
   *
   * <p>The return value is an approximation of the line number
   * in the document entity or external parsed entity where the
   * markup that triggered the event appears.</p>
   *
   * @return The line number, or -1 if none is available.
   * @see #getColumnNumber
   */
  public int getLineNumber()
  {
  	if(null == m_parent)
  	  return 0;
  	return m_parent.getLineNumber();
  }

  /**
   * Return the character position where the current document event ends.
   *
   * <p><strong>Warning:</strong> The return value from the method
   * is intended only as an approximation for the sake of error
   * reporting; it is not intended to provide sufficient information
   * to edit the character content of the original XML document.</p>
   *
   * <p>The return value is an approximation of the column number
   * in the document entity or external parsed entity where the
   * markup that triggered the event appears.</p>
   *
   * @return The column number, or -1 if none is available.
   * @see #getLineNumber
   */
  public int getColumnNumber()
  {
  	if(null == m_parent)
  	  return 0;
  	return m_parent.getColumnNumber();
  }
}