001/*
002 * Copyright (c) 2004 World Wide Web Consortium,
003 *
004 * (Massachusetts Institute of Technology, European Research Consortium for
005 * Informatics and Mathematics, Keio University). All Rights Reserved. This
006 * work is distributed under the W3C(r) Software License [1] in the hope that
007 * it will be useful, but WITHOUT ANY WARRANTY; without even the implied
008 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
009 *
010 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
011 */
012
013package org.w3c.dom.xpath;
014
015import org.w3c.dom.Node;
016import org.w3c.dom.DOMException;
017
018/**
019 *  The evaluation of XPath expressions is provided by 
020 * <code>XPathEvaluator</code>. In a DOM implementation which supports the 
021 * XPath 3.0 feature, as described above, the <code>XPathEvaluator</code> 
022 * interface will be implemented on the same object which implements the 
023 * <code>Document</code> interface permitting it to be obtained by the usual 
024 * binding-specific method such as casting or by using the DOM Level 3 
025 * getInterface method. In this case the implementation obtained from the 
026 * Document supports the XPath DOM module and is compatible with the XPath 
027 * 1.0 specification. 
028 * <p>Evaluation of expressions with specialized extension functions or 
029 * variables may not work in all implementations and is, therefore, not 
030 * portable. <code>XPathEvaluator</code> implementations may be available 
031 * from other sources that could provide specific support for specialized 
032 * extension functions or variables as would be defined by other 
033 * specifications. 
034 * <p>See also the <a href='http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document Object Model (DOM) Level 3 XPath Specification</a>.
035 */
036public interface XPathEvaluator {
037    /**
038     * Creates a parsed XPath expression with resolved namespaces. This is 
039     * useful when an expression will be reused in an application since it 
040     * makes it possible to compile the expression string into a more 
041     * efficient internal form and preresolve all namespace prefixes which 
042     * occur within the expression.
043     * @param expression The XPath expression string to be parsed.
044     * @param resolver The <code>resolver</code> permits translation of all 
045     *   prefixes, including the <code>xml</code> namespace prefix, within 
046     *   the XPath expression into appropriate namespace URIs. If this is 
047     *   specified as <code>null</code>, any namespace prefix within the 
048     *   expression will result in <code>DOMException</code> being thrown 
049     *   with the code <code>NAMESPACE_ERR</code>.
050     * @return The compiled form of the XPath expression.
051     * @exception XPathException
052     *   INVALID_EXPRESSION_ERR: Raised if the expression is not legal 
053     *   according to the rules of the <code>XPathEvaluator</code>.
054     * @exception DOMException
055     *   NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
056     *   which cannot be resolved by the specified 
057     *   <code>XPathNSResolver</code>.
058     */
059    public XPathExpression createExpression(String expression, 
060                                            XPathNSResolver resolver)
061                                            throws XPathException, DOMException;
062
063    /**
064     * Adapts any DOM node to resolve namespaces so that an XPath expression 
065     * can be easily evaluated relative to the context of the node where it 
066     * appeared within the document. This adapter works like the DOM Level 3 
067     * method <code>lookupNamespaceURI</code> on nodes in resolving the 
068     * namespaceURI from a given prefix using the current information 
069     * available in the node's hierarchy at the time lookupNamespaceURI is 
070     * called. also correctly resolving the implicit xml prefix.
071     * @param nodeResolver The node to be used as a context for namespace 
072     *   resolution.
073     * @return <code>XPathNSResolver</code> which resolves namespaces with 
074     *   respect to the definitions in scope for a specified node.
075     */
076    public XPathNSResolver createNSResolver(Node nodeResolver);
077
078    /**
079     * Evaluates an XPath expression string and returns a result of the 
080     * specified type if possible.
081     * @param expression The XPath expression string to be parsed and 
082     *   evaluated.
083     * @param contextNode The <code>context</code> is context node for the 
084     *   evaluation of this XPath expression. If the XPathEvaluator was 
085     *   obtained by casting the <code>Document</code> then this must be 
086     *   owned by the same document and must be a <code>Document</code>, 
087     *   <code>Element</code>, <code>Attribute</code>, <code>Text</code>, 
088     *   <code>CDATASection</code>, <code>Comment</code>, 
089     *   <code>ProcessingInstruction</code>, or <code>XPathNamespace</code> 
090     *   node. If the context node is a <code>Text</code> or a 
091     *   <code>CDATASection</code>, then the context is interpreted as the 
092     *   whole logical text node as seen by XPath, unless the node is empty 
093     *   in which case it may not serve as the XPath context.
094     * @param resolver The <code>resolver</code> permits translation of all 
095     *   prefixes, including the <code>xml</code> namespace prefix, within 
096     *   the XPath expression into appropriate namespace URIs. If this is 
097     *   specified as <code>null</code>, any namespace prefix within the 
098     *   expression will result in <code>DOMException</code> being thrown 
099     *   with the code <code>NAMESPACE_ERR</code>.
100     * @param type If a specific <code>type</code> is specified, then the 
101     *   result will be returned as the corresponding type.For XPath 1.0 
102     *   results, this must be one of the codes of the 
103     *   <code>XPathResult</code> interface.
104     * @param result The <code>result</code> specifies a specific result 
105     *   object which may be reused and returned by this method. If this is 
106     *   specified as <code>null</code>or the implementation does not reuse 
107     *   the specified result, a new result object will be constructed and 
108     *   returned.For XPath 1.0 results, this object will be of type 
109     *   <code>XPathResult</code>.
110     * @return The result of the evaluation of the XPath expression.For XPath 
111     *   1.0 results, this object will be of type <code>XPathResult</code>.
112     * @exception XPathException
113     *   INVALID_EXPRESSION_ERR: Raised if the expression is not legal 
114     *   according to the rules of the <code>XPathEvaluator</code>i
115     *   <br>TYPE_ERR: Raised if the result cannot be converted to return the 
116     *   specified type.
117     * @exception DOMException
118     *   NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
119     *   which cannot be resolved by the specified 
120     *   <code>XPathNSResolver</code>.
121     *   <br>WRONG_DOCUMENT_ERR: The Node is from a document that is not 
122     *   supported by this <code>XPathEvaluator</code>.
123     *   <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
124     *   context node or the request type is not permitted by this 
125     *   <code>XPathEvaluator</code>.
126     */
127    public Object evaluate(String expression, 
128                           Node contextNode, 
129                           XPathNSResolver resolver, 
130                           short type, 
131                           Object result)
132                           throws XPathException, DOMException;
133
134}