1 files changed, 169 insertions, 0 deletions
diff --git a/sca-java-2.x/tags/2.0.1-RC1/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java b/sca-java-2.x/tags/2.0.1-RC1/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java
new file mode 100644
index 0000000000..d364aa199f
--- /dev/null
+++ b/sca-java-2.x/tags/2.0.1-RC1/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java
@@ -0,0 +1,169 @@
+/*
+ * 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;
+            }
+        }
+    }
+
+}