/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
package org.apache.axiom.om.xpath;
import org.apache.axiom.om.OMAttribute;
import org.apache.axiom.om.OMContainer;
import org.apache.axiom.om.OMDocument;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMNamespace;
import org.jaxen.BaseXPath;
import org.jaxen.JaxenException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class AXIOMXPath extends BaseXPath {
private static final long serialVersionUID = -5839161412925154639L;
private Map namespaces = new HashMap();
/**
* Construct an XPath expression from a given string.
*
* @param xpathExpr the string representation of the XPath expression.
* @throws JaxenException if there is a syntax error while parsing the expression
*/
public AXIOMXPath(String xpathExpr) throws JaxenException {
super(xpathExpr, new DocumentNavigator());
}
/**
* Construct an XPath expression from a given string and initialize its
* namespace context based on a given element.
*
* @param element The element that determines the namespace context of the
* XPath expression. See {@link #addNamespaces(OMElement)}
* for more details.
* @param xpathExpr the string representation of the XPath expression.
* @throws JaxenException if there is a syntax error while parsing the expression
* or if the namespace context could not be set up
*/
public AXIOMXPath(OMElement element, String xpathExpr) throws JaxenException {
this(xpathExpr);
addNamespaces(element);
}
/**
* Construct an XPath expression from a given attribute.
* The string representation of the expression is taken from the attribute
* value, while the attribute's owner element is used to determine the
* namespace context of the expression.
*
* @param attribute the attribute to construct the expression from
* @throws JaxenException if there is a syntax error while parsing the expression
* or if the namespace context could not be set up
*/
public AXIOMXPath(OMAttribute attribute) throws JaxenException {
this(attribute.getOwner(), attribute.getAttributeValue());
}
/**
* This override captures any added namespaces, as the Jaxen BaseXPath class nor
* NamespaceContext (or SimpleNamespaceContext) exposes thier internal map of the prefixes to
* the namespaces. This method - although is not the ideal solution to the issue, attempts to
* provide an override to changing the Jaxen code.
*
* @param prefix a namespace prefix
* @param uri the URI to which the prefix matches
* @throws JaxenException if the underlying implementation throws an exception
*/
public void addNamespace(String prefix, String uri) throws JaxenException {
try {
super.addNamespace(prefix, uri);
} catch (JaxenException e) {
// the intention here is to prevent us caching a namespace, if the
// underlying implementation does not accept it
throw e;
}
namespaces.put(prefix, uri);
}
/**
* Add the namespace declarations of a given {@link OMElement} to the namespace
* context of an XPath expression. Typically this method is used with an XPath
* expression appearing in an attribute of the given element.
* <p>
* Note that the default namespace is explicitly excluded and not added to the
* namespace context. This makes the behaviour of this method consistent with
* the rules followed in XSL stylesheets. Indeed, the XSLT specification defines
* the namespace context of an XPath expression as follows:
* <blockquote>
* the set of namespace declarations are those in scope on the element which has the
* attribute in which the expression occurs; [...] the default namespace
* (as declared by xmlns) is not part of this set
* </blockquote>
*
* @param element the element to retrieve the namespace context from
* @throws JaxenException if an error occurred when adding the namespace declarations
*/
public void addNamespaces(OMElement element) throws JaxenException {
OMElement current = element;
// An element can redeclare a namespace prefix that has already been declared
// by one of its ancestors. Since we visit the tree from child to parent, we
// need to keep track of the prefixes we have already seen in order to avoid
// adding namespace declarations that are overridden by a descendant of an element.
Set seenPrefixes = new HashSet();
while (true) {
for (Iterator it = current.getAllDeclaredNamespaces(); it.hasNext(); ) {
OMNamespace ns = (OMNamespace) it.next();
if (ns != null) {
String prefix = ns.getPrefix();
// Exclude the default namespace as explained in the Javadoc above
if (prefix.length() != 0 && seenPrefixes.add(prefix)) {
addNamespace(ns.getPrefix(), ns.getNamespaceURI());
}
}
}
OMContainer parent = current.getParent();
if (parent == null || parent instanceof OMDocument) {
break;
} else {
current = (OMElement)parent;
}
}
}
/**
* Expose the prefix to namespace mapping for this expression
*
* @return a Map of namespace prefixes to the URIs
*/
public Map getNamespaces() {
return namespaces;
}
}