Fix the calculation of prefixes and add a test case

git-svn-id: http://svn.us.apache.org/repos/asf/tuscany@813042 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 142 insertions, 6 deletions

diff --git a/java/sca/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java b/java/sca/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java
index cbf8fa9f61..491837c7ee 100644
--- a/java/sca/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java
+++ b/java/sca/modules/common-xml/src/main/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelper.java
@@ -62,14 +62,27 @@ public class XPathHelper {
     public XPath newXPath() {
         return factory.newXPath();
     }
-
+    
     public XPathExpression compile(NamespaceContext context, String expression) throws XPathExpressionException {
         XPath path = newXPath();
-        path.setNamespaceContext(getNamespaceContext(expression, context));
+        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);
     }
 
-    private NamespaceContext getNamespaceContext(String expression, NamespaceContext context) {
+    /**
+     * 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);
 
         for (String prefix : getPrefixes(expression)) {
@@ -81,6 +94,11 @@ public class XPathHelper {
         return nsContext;
     }
 
+    /**
+     * Parse the XPath expression to collect all the prefixes for namespaces
+     * @param expression
+     * @return A collection of prefixes
+     */
     private Collection<String> getPrefixes(String expression) {
         List<String> prefixes = new ArrayList<String>();
         prefixes.add("");
@@ -95,14 +113,12 @@ public class XPathHelper {
                 if (XMLCharHelper.isNCName(prefix.charAt(j))) {
                     continue;
                 }
-                j--;
                 break;
             }
+            // j is before the first char of the prefix
             if (j != (prefix.length() - 1) && XMLCharHelper.isNCNameStart(prefix.charAt(j + 1))) {
                 prefixes.add(prefix.substring(j + 1));
             }
-            break;
-
         }
         return prefixes;
     }
diff --git a/java/sca/modules/common-xml/src/test/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelperTestCase.java b/java/sca/modules/common-xml/src/test/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelperTestCase.java
new file mode 100644
index 0000000000..6bd37cb34e
--- /dev/null
+++ b/java/sca/modules/common-xml/src/test/java/org/apache/tuscany/sca/common/xml/xpath/XPathHelperTestCase.java
@@ -0,0 +1,120 @@
+/*
+ * 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 javax.xml.stream.XMLStreamReader;
+import javax.xml.xpath.XPath;
+import javax.xml.xpath.XPathConstants;
+import javax.xml.xpath.XPathExpression;
+
+import org.apache.tuscany.sca.common.xml.dom.DOMHelper;
+import org.apache.tuscany.sca.common.xml.stax.StAXHelper;
+import org.apache.tuscany.sca.core.DefaultExtensionPointRegistry;
+import org.apache.tuscany.sca.core.ExtensionPointRegistry;
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+
+/**
+ * 
+ */
+public class XPathHelperTestCase {
+    private static XPathHelper xpathHelper;
+    private static StAXHelper staxHelper;
+    private static DOMHelper domHelper;
+
+    private static String XML =
+        "<r:root name=\"root\" xmlns:r=\"http://root\">" + "<c:child xmlns:c=\"http://child\" name=\"child\">"
+            + "<c:child1 xmlns:c=\"http://child1\" name=\"child1\"/>"
+            + "</c:child>"
+            + "</r:root>";
+
+    private static String XPATH =
+        "<policySet attachTo=\"//c:child1[@name='child1']\" xmlns:c=\"http://child1\" xmlns=\"http://p\">" + "<child xmlns:c=\"http://c2\"/></policySet>";
+
+    /**
+     * @throws java.lang.Exception
+     */
+    @BeforeClass
+    public static void setUpBeforeClass() throws Exception {
+        ExtensionPointRegistry registry = new DefaultExtensionPointRegistry();
+        xpathHelper = XPathHelper.getInstance(registry);
+        domHelper = DOMHelper.getInstance(registry);
+        staxHelper = StAXHelper.getInstance(registry);
+    }
+
+    @Test
+    public void testNewXPath() {
+        XPath path = xpathHelper.newXPath();
+        Assert.assertNotNull(path);
+    }
+
+    @Test
+    public void testCompile() throws Exception {
+        XMLStreamReader reader = staxHelper.createXMLStreamReader(XPATH);
+        reader.nextTag();
+        String xpath = reader.getAttributeValue(null, "attachTo");
+        XPathExpression expression = xpathHelper.compile(reader.getNamespaceContext(), xpath);
+        // Advance the reader so that the namespace context changes its prefix/namespace mapping
+        reader.nextTag();
+        reader.close();
+
+        Document doc = domHelper.load(XML);
+        NodeList nodes = (NodeList)expression.evaluate(doc, XPathConstants.NODESET);
+        Assert.assertEquals(1, nodes.getLength());
+        Node node = nodes.item(0);
+        Assert.assertTrue(node instanceof Element);
+        Assert.assertEquals(node.getNodeName(), "c:child1");
+    }
+
+    @Test
+    public void testCompile2() throws Exception {
+        XMLStreamReader reader = staxHelper.createXMLStreamReader(XPATH);
+        reader.nextTag();
+        String xpathExp = reader.getAttributeValue(null, "attachTo");
+        XPath xpath = xpathHelper.newXPath();
+        // Compile the expression without taking a snapshot of the namespace context
+        XPathExpression expression = xpathHelper.compile(xpath, reader.getNamespaceContext(), xpathExp);
+        // Advance the reader so that the namespace context changes its prefix/namespace mapping
+        reader.nextTag();
+        reader.close();
+
+        Document doc = domHelper.load(XML);
+        NodeList nodes = (NodeList)expression.evaluate(doc, XPathConstants.NODESET);
+        Assert.assertEquals(1, nodes.getLength());
+        Node node = nodes.item(0);
+        Assert.assertTrue(node instanceof Element);
+        Assert.assertEquals(node.getNodeName(), "c:child1");
+    }
+
+    /**
+     * @throws java.lang.Exception
+     */
+    @AfterClass
+    public static void tearDownAfterClass() throws Exception {
+        xpathHelper = null;
+    }
+
+}