/*
* Copyright 2002-2005 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: XPathEvaluatorImpl.java,v 1.2.4.1 2005/09/10 04:04:07 jeffsuttor Exp $
*/
package com.sun.org.apache.xpath.internal.domapi;
import javax.xml.transform.TransformerException;
import com.sun.org.apache.xml.internal.utils.PrefixResolver;
import com.sun.org.apache.xpath.internal.XPath;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;
import com.sun.org.apache.xpath.internal.res.XPATHMessages;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.xpath.XPathEvaluator;
import org.w3c.dom.xpath.XPathException;
import org.w3c.dom.xpath.XPathExpression;
import org.w3c.dom.xpath.XPathNSResolver;
/**
*
* The class provides an implementation of XPathEvaluator according
* to the DOM L3 XPath Specification, Working Group Note 26 February 2004.
*
* <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>.</p>
*
* </p>The evaluation of XPath expressions is provided by
* <code>XPathEvaluator</code>, which will provide evaluation of XPath 1.0
* expressions with no specialized extension functions or variables. It is
* expected that the <code>XPathEvaluator</code> interface will be
* implemented on the same object which implements the <code>Document</code>
* interface in an implementation which supports the XPath DOM module.
* <code>XPathEvaluator</code> implementations may be available from other
* sources that may provide support for special extension functions or
* variables which are not defined in this specification.</p>
*
* @see org.w3c.dom.xpath.XPathEvaluator
*
* @xsl.usage internal
*/
public final class XPathEvaluatorImpl implements XPathEvaluator {
/**
* This prefix resolver is created whenever null is passed to the
* evaluate method. Its purpose is to satisfy the DOM L3 XPath API
* requirement that if a null prefix resolver is used, an exception
* should only be thrown when an attempt is made to resolve a prefix.
*/
private class DummyPrefixResolver implements PrefixResolver {
/**
* Constructor for DummyPrefixResolver.
*/
DummyPrefixResolver() {}
/**
* @exception DOMException
* NAMESPACE_ERR: Always throws this exceptionn
*
* @see com.sun.org.apache.xml.internal.utils.PrefixResolver#getNamespaceForPrefix(String, Node)
*/
public String getNamespaceForPrefix(String prefix, Node context) {
String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_NULL_RESOLVER, null);
throw new DOMException(DOMException.NAMESPACE_ERR, fmsg); // Unable to resolve prefix with null prefix resolver.
}
/**
* @exception DOMException
* NAMESPACE_ERR: Always throws this exceptionn
*
* @see com.sun.org.apache.xml.internal.utils.PrefixResolver#getNamespaceForPrefix(String)
*/
public String getNamespaceForPrefix(String prefix) {
return getNamespaceForPrefix(prefix,null);
}
/**
* @see com.sun.org.apache.xml.internal.utils.PrefixResolver#handlesNullPrefixes()
*/
public boolean handlesNullPrefixes() {
return false;
}
/**
* @see com.sun.org.apache.xml.internal.utils.PrefixResolver#getBaseIdentifier()
*/
public String getBaseIdentifier() {
return null;
}
}
/**
* The document to be searched to parallel the case where the XPathEvaluator
* is obtained by casting a Document.
*/
private final Document m_doc;
/**
* Constructor for XPathEvaluatorImpl.
*
* @param doc The document to be searched, to parallel the case where''
* the XPathEvaluator is obtained by casting the document.
*/
public XPathEvaluatorImpl(Document doc) {
m_doc = doc;
}
/**
* Constructor in the case that the XPath expression can be evaluated
* without needing an XML document at all.
*
*/
public XPathEvaluatorImpl() {
m_doc = null;
}
/**
* Creates a parsed XPath expression with resolved namespaces. This is
* useful when an expression will be reused in an application since it
* makes it possible to compile the expression string into a more
* efficient internal form and preresolve all namespace prefixes which
* occur within the expression.
*
* @param expression The XPath expression string to be parsed.
* @param resolver The <code>resolver</code> permits translation of
* prefixes within the XPath expression into appropriate namespace URIs
* . If this is specified as <code>null</code>, any namespace prefix
* within the expression will result in <code>DOMException</code>
* being thrown with the code <code>NAMESPACE_ERR</code>.
* @return The compiled form of the XPath expression.
* @exception XPathException
* INVALID_EXPRESSION_ERR: Raised if the expression is not legal
* according to the rules of the <code>XPathEvaluator</code>i
* @exception DOMException
* NAMESPACE_ERR: Raised if the expression contains namespace prefixes
* which cannot be resolved by the specified
* <code>XPathNSResolver</code>.
*
* @see org.w3c.dom.xpath.XPathEvaluator#createExpression(String, XPathNSResolver)
*/
public XPathExpression createExpression(
String expression,
XPathNSResolver resolver)
throws XPathException, DOMException {
try {
// If the resolver is null, create a dummy prefix resolver
XPath xpath = new XPath(expression,null,
((null == resolver) ? new DummyPrefixResolver() : ((PrefixResolver)resolver)),
XPath.SELECT);
return new XPathExpressionImpl(xpath, m_doc);
} catch (TransformerException e) {
// Need to pass back exception code DOMException.NAMESPACE_ERR also.
// Error found in DOM Level 3 XPath Test Suite.
if(e instanceof XPathStylesheetDOM3Exception)
throw new DOMException(DOMException.NAMESPACE_ERR,e.getMessageAndLocation());
else
throw new XPathException(XPathException.INVALID_EXPRESSION_ERR,e.getMessageAndLocation());
}
}
/**
* Adapts any DOM node to resolve namespaces so that an XPath expression
* can be easily evaluated relative to the context of the node where it
* appeared within the document. This adapter works like the DOM Level 3
* method <code>lookupNamespaceURI</code> on nodes in resolving the
* namespaceURI from a given prefix using the current information available
* in the node's hierarchy at the time lookupNamespaceURI is called, also
* correctly resolving the implicit xml prefix.
*
* @param nodeResolver The node to be used as a context for namespace
* resolution.
* @return <code>XPathNSResolver</code> which resolves namespaces with
* respect to the definitions in scope for a specified node.
*
* @see org.w3c.dom.xpath.XPathEvaluator#createNSResolver(Node)
*/
public XPathNSResolver createNSResolver(Node nodeResolver) {
return new XPathNSResolverImpl((nodeResolver.getNodeType() == Node.DOCUMENT_NODE)
? ((Document) nodeResolver).getDocumentElement() : nodeResolver);
}
/**
* Evaluates an XPath expression string and returns a result of the
* specified type if possible.
*
* @param expression The XPath expression string to be parsed and
* evaluated.
* @param contextNode The <code>context</code> is context node for the
* evaluation of this XPath expression. If the XPathEvaluator was
* obtained by casting the <code>Document</code> then this must be
* owned by the same document and must be a <code>Document</code>,
* <code>Element</code>, <code>Attribute</code>, <code>Text</code>,
* <code>CDATASection</code>, <code>Comment</code>,
* <code>ProcessingInstruction</code>, or <code>XPathNamespace</code>
* node. If the context node is a <code>Text</code> or a
* <code>CDATASection</code>, then the context is interpreted as the
* whole logical text node as seen by XPath, unless the node is empty
* in which case it may not serve as the XPath context.
* @param resolver The <code>resolver</code> permits translation of
* prefixes within the XPath expression into appropriate namespace URIs
* . If this is specified as <code>null</code>, any namespace prefix
* within the expression will result in <code>DOMException</code>
* being thrown with the code <code>NAMESPACE_ERR</code>.
* @param type If a specific <code>type</code> is specified, then the
* result will be coerced to return the specified type relying on
* XPath type conversions and fail if the desired coercion is not
* possible. This must be one of the type codes of
* <code>XPathResult</code>.
* @param result The <code>result</code> specifies a specific result
* object which may be reused and returned by this method. If this is
* specified as <code>null</code>or the implementation does not reuse
* the specified result, a new result object will be constructed and
* returned.For XPath 1.0 results, this object will be of type
* <code>XPathResult</code>.
* @return The result of the evaluation of the XPath expression.For XPath
* 1.0 results, this object will be of type <code>XPathResult</code>.
* @exception XPathException
* INVALID_EXPRESSION_ERR: Raised if the expression is not legal
* according to the rules of the <code>XPathEvaluator</code>i
* <br>TYPE_ERR: Raised if the result cannot be converted to return the
* specified type.
* @exception DOMException
* NAMESPACE_ERR: Raised if the expression contains namespace prefixes
* which cannot be resolved by the specified
* <code>XPathNSResolver</code>.
* <br>WRONG_DOCUMENT_ERR: The Node is from a document that is not
* supported by this XPathEvaluator.
* <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath
* context node.
*
* @see org.w3c.dom.xpath.XPathEvaluator#evaluate(String, Node, XPathNSResolver, short, XPathResult)
*/
public Object evaluate(
String expression,
Node contextNode,
XPathNSResolver resolver,
short type,
Object result)
throws XPathException, DOMException {
XPathExpression xpathExpression = createExpression(expression, resolver);
return xpathExpression.evaluate(contextNode, type, result);
}
}
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