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/*
* 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.tuscany.sca.common.xml.xpath;
import java.util.Collection;
import java.util.HashSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.apache.tuscany.sca.common.xml.stax.reader.NamespaceContextImpl;
import org.apache.tuscany.sca.core.ExtensionPointRegistry;
import org.apache.tuscany.sca.core.FactoryExtensionPoint;
import org.apache.tuscany.sca.core.UtilityExtensionPoint;
/**
* Helper for XPath operations
*/
public class XPathHelper {
private XPathFactory factory;
/**
* @param factory
*/
public XPathHelper(XPathFactory factory) {
super();
this.factory = factory;
}
public XPathHelper(ExtensionPointRegistry registry) {
FactoryExtensionPoint factories = registry.getExtensionPoint(FactoryExtensionPoint.class);
this.factory = factories.getFactory(XPathFactory.class);
}
public static XPathHelper getInstance(ExtensionPointRegistry registry) {
UtilityExtensionPoint utilities = registry.getExtensionPoint(UtilityExtensionPoint.class);
return utilities.getUtility(XPathHelper.class);
}
public XPath newXPath() {
return factory.newXPath();
}
public XPathExpression compile(NamespaceContext context, String expression) throws XPathExpressionException {
XPath path = newXPath();
context = getNamespaceContext(expression, context);
return compile(path, context, expression);
}
public XPathExpression compile(XPath path, NamespaceContext context, String expression)
throws XPathExpressionException {
path.setNamespaceContext(context);
return path.compile(expression);
}
/**
* Take a snapshot of the given namespace context based on the prefixes found in the expression.
* In StAX, the prefix/namespace mapping in the namespace context can change as the event moves
* @param expression
* @param context
* @return
*/
public NamespaceContext getNamespaceContext(String expression, NamespaceContext context) {
NamespaceContextImpl nsContext = new NamespaceContextImpl(null);
boolean found = false;
for (String prefix : getPrefixes(expression)) {
String namespace = context.getNamespaceURI(prefix);
if (namespace != null && !XMLConstants.NULL_NS_URI.equals(namespace)) {
nsContext.register(prefix, namespace);
if ( (namespace.equals("http://docs.oasis-open.org/ns/opencsa/sca/200912")) && !prefix.equals(XMLConstants.DEFAULT_NS_PREFIX))
found = true;
}
}
if(!found) {
nsContext.register("__sca", "http://docs.oasis-open.org/ns/opencsa/sca/200912");
}
return nsContext;
}
/**
* Registers a prefix in an existing NamespaceContext
* @param prefix
* @param namespace
* @param context
*/
public void registerPrefix(String prefix, String namespace, NamespaceContext context) {
NamespaceContextImpl nsContext = (NamespaceContextImpl) context;
nsContext.register(prefix, namespace);
}
/**
* Parse the XPath expression to collect all the prefixes for namespaces
* @param expression
* @return A collection of prefixes
*/
private Collection<String> getPrefixes(String expression) {
Collection<String> prefixes = new HashSet<String>();
prefixes.add(XMLConstants.DEFAULT_NS_PREFIX);
Pattern pattern = Pattern.compile("([a-zA-Z.]+):([a-zA-Z.]+)");
Matcher matcher = pattern.matcher(expression);
while (matcher.find()) {
String prefix = extractNCName(matcher.group(1), true);
String local = extractNCName(matcher.group(2), false);
if (prefix != null && local != null) {
prefixes.add(prefix);
}
}
return prefixes;
}
private String extractNCName(String str, boolean reverse) {
if (str.length() < 1) {
return null;
}
if (!reverse) {
if (!XMLCharHelper.isNCNameStart(str.charAt(0))) {
return null;
}
int i = 0, j = str.length();
// Find the last non-NCName char
for (; i < j; i++) {
if (!XMLCharHelper.isNCName(str.charAt(i))) {
break;
}
}
return str.substring(0, i);
} else {
int j = str.length() - 1;
// Find the first non-NCName char
for (; j >= 0; j--) {
if (!XMLCharHelper.isNCName(str.charAt(j))) {
break;
}
}
// j is before the first char of the prefix
if (j != (str.length() - 1) && XMLCharHelper.isNCNameStart(str.charAt(j + 1))) {
return str.substring(j + 1);
} else {
return null;
}
}
}
}
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