/*
* 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.axiom.om.impl.common;
import org.apache.axiom.om.OMContainer;
import org.apache.axiom.om.OMDocument;
import org.apache.axiom.om.OMNode;
import org.apache.axiom.om.OMSerializable;
import org.apache.axiom.om.OMSourcedElement;
import org.apache.axiom.om.impl.OMNodeEx;
/**
* Refer to the test, org.apache.axiom.om.OMNavigatorTest, to find out how to use features like
* isNavigable, isComplete and step.
*/
public class OMNavigator {
/** Field node */
protected OMSerializable node;
/** Field visited */
private boolean visited;
/** Field next */
private OMSerializable next;
// root is the starting element. Once the navigator comes back to the
// root, the traversal is terminated
/** Field root */
private OMSerializable root;
/** Field backtracked */
private boolean backtracked;
// flags that tell the status of the navigator
/** Field end */
private boolean end = false;
/** Field start */
private boolean start = true;
// Indicates if an OMSourcedElement with an OMDataSource should
// be considered as an interior node or a leaf node.
private boolean isDataSourceALeaf = false;
/** Constructor OMNavigator. */
public OMNavigator() {
}
/**
* Constructor OMNavigator.
*
* @param node
*/
public OMNavigator(OMSerializable node) {
init(node);
}
/**
* Method init.
*
* @param node
*/
public void init(OMSerializable node) {
next = node;
root = node;
backtracked = false;
}
/**
* Indicate if an OMSourcedElement with a OMDataSource
* should be considered as an interior element node or as
* a leaf.
* @param value boolean
*/
public void setDataSourceIsLeaf(boolean value) {
isDataSourceALeaf = value;
}
/**
* Get the next information item.
*
* @return the next information item in the sequence of preorder traversal. Note however that a
* container (document or element) is treated slightly differently. Once the container
* is passed it returns the same item in the next encounter as well.
*/
public OMSerializable getNext() {
if (next == null) {
return null;
}
node = next;
visited = backtracked;
backtracked = false;
updateNextNode();
// set the starting and ending flags
if (root.equals(node)) {
if (!start) {
end = true;
} else {
start = false;
}
}
return node;
}
/**
* Get the next node. This method only exists for compatibility with existing code. It may throw
* a {@link ClassCastException} if an attempt is made to use it on a navigator that was created
* from an {@link OMDocument}.
*
* @return the next node
* @see #getNext()
*/
public OMNode next() {
return (OMNode)getNext();
}
/** Private method to encapsulate the searching logic. */
private void updateNextNode() {
if (!isLeaf(next) && !visited) {
OMNode firstChild = _getFirstChild((OMContainer) next);
if (firstChild != null) {
next = firstChild;
} else if (next.isComplete()) {
backtracked = true;
} else {
next = null;
}
} else {
if (next instanceof OMDocument) {
next = null;
} else {
OMNode nextNode = (OMNode)next;
OMContainer parent = nextNode.getParent();
OMNode nextSibling = getNextSibling(nextNode);
if (nextSibling != null) {
next = nextSibling;
} else if ((parent != null) && parent.isComplete()) {
next = parent;
backtracked = true;
} else {
next = null;
}
}
}
}
/**
* @param n OMNode
* @return true if this OMNode should be considered a leaf node
*/
private boolean isLeaf(OMSerializable n) {
if (n instanceof OMContainer) {
return this.isDataSourceALeaf && isOMSourcedElement(n) && n != root;
} else {
return true;
}
}
private boolean isOMSourcedElement(OMSerializable node) {
if (node instanceof OMSourcedElement) {
try {
return ((OMSourcedElement)node).getDataSource() != null;
} catch (UnsupportedOperationException e) {
// Operation unsupported for some implementations
return false;
}
} else {
return false;
}
}
/**
* @param node
* @return first child or null
*/
private OMNode _getFirstChild(OMContainer node) {
if (isOMSourcedElement(node)) {
OMNode first = node.getFirstOMChild();
OMNode sibling = first;
while (sibling != null) {
sibling = sibling.getNextOMSibling();
}
return first;
} else {
return ((IContainer)node).getFirstOMChildIfAvailable();
}
}
/**
* @param node
* @return next sibling or null
*/
private OMNode getNextSibling(OMNode node) {
if (isOMSourcedElement(node)) {
return node.getNextOMSibling();
} else {
return ((OMNodeEx) node).getNextOMSiblingIfAvailable();
}
}
/**
* Method visited.
*
* @return Returns boolean.
*/
public boolean visited() {
return visited;
}
/**
* This is a very special method. This allows the navigator to step once it has reached the
* existing OM. At this point the isNavigable method will return false but the isComplete method
* may return false which means that the navigating the given element is not complete and the
* navigator cannot proceed.
*/
public void step() {
if (!end) {
next = node;
updateNextNode();
}
}
/**
* Returns the navigable status.
*
* @return Returns boolean.
*/
public boolean isNavigable() {
if (end) {
return false;
} else {
return !(next == null);
}
}
/**
* Returns the completed status.
*
* @return Returns boolean.
*/
public boolean isCompleted() {
return end;
}
}