Navigating with XTreeCursor

You can use the XTreeCursor interface to view your data.

About this task

Suppose the sequence that results from evaluating an XPath or XQuery expression or an XSLT stylesheet contains nodes. You will find it very convenient to access the contents of those nodes by applying further XPath or XQuery expressions to those nodes. However, you might also choose to navigate through the tree structure associated with a node directly through the XML API.

Procedure

Example

The following example shows how you can use the methods on the XTreeCursor interface to navigate through the tree containing your XML data.

/* Contents of library.xml

<library>
  <book title='Ulysses'><author><first>James</first><last>Joyce</last></author></book>
  <book title='Ada'><author><first>Vladimir</first><last>Nabokov</last></author></book>
</library>
*/

XItemFactory factory = XFactory.newInstance().getItemFactory();
XItemView item = factory.item(new StreamSource("library.xml"));

// 'tree' is initially positioned at the same node as
// 'item' - that is, the document node of the input
XTreeCursor tree = item.getTreeCursor();

// Position tree cursor to "library" element
tree.toFirstChild();

// Position tree cursor to white-space text node
tree.toFirstChild();

// Position to first "book" element
tree.toNextSibling();

// Position to white-space text node
tree.toNextSibling();

// Position to second "book" element
tree.toNextSibling();

// Create a second instance of XTreeCursor that is initially
// positioned at the same node as 'tree' - that is, the
// second "book" element
XTreeCursor secondBook = tree.getTreeCursor();

// Position 'tree' to "library" element
tree.toParent();

// Position 'secondBook' to "title" attribute
secondBook.toFirstAttribute();

The following example navigates through all the nodes in a tree in a depth-first fashion.

XItemFactory factory = XFactory.newInstance().getItemFactory();
XItemView item = factory.item(new StreamSource("library.xml"));

XTreeCursor tree = item.getTreeCursor();
boolean hasMoreNodes = true;

do {
    // Process current node

    if (tree.toFirstAttribute()) {
        do {
            // Process attributes
        } while (tree.toNextAttribute());
        tree.toParent();
    }

    if (tree.toFirstNamespace()) {
        do {
            // Process namespaces
        } while (tree.toFirstNamespace());
        tree.toParent();
    }

    boolean foundNext = false;

    // If the current node has a child, visit it next
    // If there's no child, go to the next sibling
    if (tree.toFirstChild() || tree.toNextSibling()) {
        foundNext = true;

    // If there's no child and no sibling, find an
    // ancestor's sibling instead.
    } else {
        do {
            hasMoreNodes = tree.toParent();
            if (hasMoreNodes) {
                foundNext = tree.toNextSibling();
            }
        } while (hasMoreNodes && !foundNext);
    }
} while (hasMoreNodes);



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Last updatedLast updated: Sep 19, 2011 7:16:32 PM CDT
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