001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements. See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership. The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the  "License");
007     * you may not use this file except in compliance with the License.
008     * You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    /*
019     * $Id: ExpressionContext.java 468637 2006-10-28 06:51:02Z minchau $
020     */
021    package org.apache.xalan.extensions;
022    
023    import javax.xml.transform.ErrorListener;
024    
025    import org.apache.xpath.objects.XObject;
026    import org.w3c.dom.Node;
027    import org.w3c.dom.traversal.NodeIterator;
028    
029    /**
030     * An object that implements this interface can supply
031     * information about the current XPath expression context.
032     */
033    public interface ExpressionContext
034    {
035    
036      /**
037       * Get the current context node.
038       * @return The current context node.
039       */
040      public Node getContextNode();
041    
042      /**
043       * Get the current context node list.
044       * @return An iterator for the current context list, as
045       * defined in XSLT.
046       */
047      public NodeIterator getContextNodes();
048      
049      /**
050       * Get the error listener.
051       * @return The registered error listener.
052       */
053      public ErrorListener getErrorListener();
054    
055      /**
056       * Get the value of a node as a number.
057       * @param n Node to be converted to a number.  May be null.
058       * @return value of n as a number.
059       */
060      public double toNumber(Node n);
061    
062      /**
063       * Get the value of a node as a string.
064       * @param n Node to be converted to a string.  May be null.
065       * @return value of n as a string, or an empty string if n is null.
066       */
067      public String toString(Node n);
068    
069      /**
070       * Get a variable based on it's qualified name.
071       *
072       * @param qname The qualified name of the variable.
073       *
074       * @return The evaluated value of the variable.
075       *
076       * @throws javax.xml.transform.TransformerException
077       */
078      public XObject getVariableOrParam(org.apache.xml.utils.QName qname)
079                throws javax.xml.transform.TransformerException;
080      
081      /**
082       * Get the XPathContext that owns this ExpressionContext.
083       * 
084       * Note: exslt:function requires the XPathContext to access
085       * the variable stack and TransformerImpl.
086       * 
087       * @return The current XPathContext.
088       * @throws javax.xml.transform.TransformerException
089       */
090      public org.apache.xpath.XPathContext getXPathContext()
091                throws javax.xml.transform.TransformerException;
092    
093    }