package org.apache.xmlbeans.impl.xpathgen;
import org.apache.xmlbeans.XmlCursor;
import org.apache.xmlbeans.XmlCursor.TokenType;
import javax.xml.namespace.QName;
import javax.xml.namespace.NamespaceContext;
/**
* Generates an XPath String that points to a given position in an XML document
*/
public class XPathGenerator
{
/**
* Generates an XPath pointing to the position in the document indicated by <code>node</code>.
* <p>If the <code>context</code> parameter is null, the XPath is absolute, otherwise the
* XPath will be relative to the position indicated by <code>context</code>.</p>
* <p>Note: the cursor position for the <code>node</code> parameter is not preserved</p>
* @param node the position in the document that the generated path will point to
* @param context the context node; the generated path will be relative to it if not null and if
* pointing to an element on the path from the document root to <code>node</code>
* @param nsctx a namespace context that will be used to obtain prefixes; a (non-default)
* namespace mapping must be available for all required namespace URIs
* @return the generated path as a <code>String</code>
* @throws XPathGenerationException if the path could not be generated: the cursor is in a bad
* position (like over a comment) or no prefix mapping was found for one of the namespace URIs
*/
public static String generateXPath(XmlCursor node, XmlCursor context, NamespaceContext nsctx)
throws XPathGenerationException
{
if (node == null)
throw new IllegalArgumentException("Null node");
if (nsctx == null)
throw new IllegalArgumentException("Null namespace context");
TokenType tt = node.currentTokenType();
if (context != null && node.isAtSamePositionAs(context))
return ".";
switch (tt.intValue())
{
case TokenType.INT_ATTR:
QName name = node.getName();
node.toParent();
String pathToParent = generateInternal(node, context, nsctx);
return pathToParent + '/' + '@' + qnameToString(name, nsctx);
case TokenType.INT_NAMESPACE:
name = node.getName();
node.toParent();
pathToParent = generateInternal(node, context, nsctx);
String prefix = name.getLocalPart();
if (prefix.length() == 0)
return pathToParent + "/@xmlns";
else
return pathToParent + "/@xmlns:" + prefix;
case TokenType.INT_START:
case TokenType.INT_STARTDOC:
return generateInternal(node, context, nsctx);
case TokenType.INT_TEXT:
int nrOfTextTokens = countTextTokens(node);
node.toParent();
pathToParent = generateInternal(node, context, nsctx);
if (nrOfTextTokens == 0)
return pathToParent + "/text()";
else
return pathToParent + "/text()[position()=" + nrOfTextTokens + ']';
default:
throw new XPathGenerationException("Cannot generate XPath for cursor position: " +
tt.toString());
}
}
private static String generateInternal(XmlCursor node, XmlCursor context, NamespaceContext nsctx)
throws XPathGenerationException
{
if (node.isStartdoc())
return "";
if (context != null && node.isAtSamePositionAs(context))
return ".";
assert node.isStart();
QName name = node.getName();
XmlCursor d = node.newCursor();
if (!node.toParent())
return "/" + name;
int elemIndex = 0, i = 1;
node.push();
if (!node.toChild(name))
throw new IllegalStateException("Must have at least one child with name: " + name);
do
{
if (node.isAtSamePositionAs(d))
elemIndex = i;
else
i++;
} while (node.toNextSibling(name));
node.pop();
d.dispose();
String pathToParent = generateInternal(node, context, nsctx);
return i == 1 ? pathToParent + '/' + qnameToString(name, nsctx) :
pathToParent + '/' + qnameToString(name, nsctx) + '[' + elemIndex + ']';
}
private static String qnameToString(QName qname, NamespaceContext ctx)
throws XPathGenerationException
{
String localName = qname.getLocalPart();
String uri = qname.getNamespaceURI();
if (uri.length() == 0)
return localName;
String prefix = qname.getPrefix();
if (prefix != null && prefix.length() > 0)
{
// Try to use the same prefix if it maps to the right URI
String mappedUri = ctx.getNamespaceURI(prefix);
if (uri.equals(mappedUri))
return prefix + ':' + localName;
}
// The prefix is not specified, or it is not mapped to the right URI
prefix = ctx.getPrefix(uri);
if (prefix == null)
throw new XPathGenerationException("Could not obtain a prefix for URI: " + uri);
if (prefix.length() == 0)
throw new XPathGenerationException("Can not use default prefix in XPath for URI: " + uri);
return prefix + ':' + localName;
}
/**
* Computes how many text nodes the
* @param c the position in the document
* @return how many text nodes occur before the position determined by <code>c</code>
*/
private static int countTextTokens(XmlCursor c)
{
int k = 0;
int l = 0;
XmlCursor d = c.newCursor();
c.push();
c.toParent();
TokenType tt = c.toFirstContentToken();
while (!tt.isEnd())
{
if (tt.isText())
{
if (c.comparePosition(d) > 0)
// We have moved after the initial position
l++;
else
k++;
}
else if (tt.isStart())
c.toEndToken();
tt = c.toNextToken();
}
c.pop();
return l == 0 ? 0 : k;
}
public static void main(String[] args) throws org.apache.xmlbeans.XmlException
{
String xml =
"<root>\n" +
"<ns:a xmlns:ns=\"http://a.com\"><b foo=\"value\">text1<c/>text2<c/>text3<c>text</c>text4</b></ns:a>\n" +
"</root>";
NamespaceContext ns = new NamespaceContext() {
public String getNamespaceURI(String prefix)
{
if ("ns".equals(prefix))
return "http://a.com";
else
return null;
}
public String getPrefix(String namespaceUri)
{
return null;
}
public java.util.Iterator getPrefixes(String namespaceUri)
{
return null;
}
};
XmlCursor c = org.apache.xmlbeans.XmlObject.Factory.parse(xml).newCursor();
c.toFirstContentToken(); // on <root>
c.toFirstContentToken(); // on <a>
c.toFirstChild(); // on <b>
c.toFirstChild(); // on <c>
c.push(); System.out.println(generateXPath(c, null, ns)); c.pop();
c.toNextSibling();
c.toNextSibling(); // on the last <c>
c.push(); System.out.println(generateXPath(c, null, ns)); c.pop();
XmlCursor d = c.newCursor();
d.toParent();
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
d.toParent();
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
c.toFirstContentToken(); // on text content of the last <c>
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
c.toParent();
c.toPrevToken(); // on text content before the last <c>
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
c.toParent(); // on <b>
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
c.toFirstAttribute(); // on the "foo" attribute
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
c.toParent();
c.toParent();
c.toNextToken(); // on the "xmlns:ns" attribute
c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
c.push(); System.out.println(generateXPath(c, null, ns)); c.pop();
}
}