I have developed GUI tool the displays an XML document as an editable JTree, and the user can select a node in the JTree and attempt to change the actual nodes value in the XML document.
The problem that I'm having is with constructing the correct Xpath query that attempts the actual update.
Here is GUI of the JTree showing which element was selected & should be edited:
Its a very large XMl, so here the collapsed snippet of the XML:
UPDATE (IGNORE ATTEMPT 1 & 2, 1ST ISSUE WAS RESOLVED, GO TO ATTEMPTS 3 & 4)
Attempt 1 # (relevant Java method that attempts to create XPath query to update a nodes value):
public void updateXmlData(JTree jTree, org.w3c.dom.Document doc, TreeNode parentNode, String oldValue, String newValue) throws XPathExpressionException {
System.out.println("Selected path=" + jTree.getSelectionPath().toString());
String[] pathTockens = jTree.getSelectionPath().toString().split(",");
StringBuilder sb = new StringBuilder();
//for loop to construct xpath query
for (int i = 0; i < pathTockens.length - 1; i++) {
if (i == 0) {
sb.append("//");
} else {
sb.append(pathTockens[i].trim());
sb.append("/");
}
}//end for loop
sb.append("text()");
System.out.println("Constructed XPath Query:" + sb.toString());
//new xpath
XPath xpath = XPathFactory.newInstance().newXPath();
//compile query
NodeList nodes = (NodeList) xpath.compile(sb.toString()).evaluate(doc, XPathConstants.NODESET);
//Make the change on the selected nodes
for (int idx = 0; idx < nodes.getLength(); idx++) {
Node value = nodes.item(idx).getAttributes().getNamedItem("value");
String val = value.getNodeValue();
value.setNodeValue(val.replaceAll(oldValue, newValue));
}
//set the new updated xml doc
SingleTask.currentTask.setDoc(doc);
}
Console logs:
Selected path=[C:\Users\xyz\Documents\XsdToXmlFiles\sampleIngest.xml, Ingest, Property_Maps, identifier, identifieXYZ]
Constructed XPath Query://Ingest/Property_Maps/identifier/text()
Jan 26, 2021 2:04:16 PM com.xyz.XmlToXsdValidator.Views.EditXmlTreeNodeDialogJFrame jButtonOkEditActionPerformed
SEVERE: null
javax.xml.transform.TransformerException: Unable to evaluate expression using this context
at com.sun.org.apache.xpath.internal.XPath.execute(XPath.java:368)
As you can see in the logs:
Selected path=[C:\Users\xyz\Documents\XsdToXmlFiles\sampleIngest.xml, Ingest, Property_Maps, identifier, identifieXYZ]
Constructed XPath Query://Ingest/Property_Maps/identifier/text()
The paths are correct, basically Ingest->Property_Maps->identifier->text()
But Im getting:
javax.xml.transform.TransformerException: Unable to evaluate expression using this context
Attempt 2 # (relevant Java method that attempts to create XPath query to update a nodes value):
public void updateXmlData(JTree jTree, org.w3c.dom.Document doc, TreeNode parentNode, String oldValue, String newValue) throws XPathExpressionException {
// Locate the node(s) with xpath
System.out.println("Selected path=" + jTree.getSelectionPath().toString());
String[] pathTockens = jTree.getSelectionPath().toString().split(",");
StringBuilder sb = new StringBuilder();
//loop to construct xpath query
for (int i = 0; i < pathTockens.length - 1; i++) {
if (i == 0) {
sb.append("//");
} else {
sb.append(pathTockens[i].trim());
sb.append("/");
}
}//end loop
sb.append("[text()=");
sb.append("'");
sb.append(oldValue);
sb.append("']");
int lastIndexOfPathChar = sb.lastIndexOf("/");
sb.replace(lastIndexOfPathChar, lastIndexOfPathChar + 1, "");
System.out.println("Constructed XPath Query:" + sb.toString());
//new xpath instance
XPath xpath = XPathFactory.newInstance().newXPath();
NodeList nodes = (NodeList) xpath.evaluate(sb.toString(), doc, XPathConstants.NODESET);
//Make the change on the selected nodes
for (int idx = 0; idx < nodes.getLength(); idx++) {
Node value = nodes.item(idx).getAttributes().getNamedItem("value");
String val = value.getNodeValue();
value.setNodeValue(val.replaceAll(oldValue, newValue));
}
SingleTask.currentTask.setDoc(doc);
}
I was able to resolve the exception based Andreas comment, and there are no more exceptions/errors, however the XPath query does not find selected nodes. Returns empty
New updated code:
Attempt # 3 Using custom namespace resolver. References: https://www.kdgregory.com/index.php?page=xml.xpath
public boolean updateXmlData(JTree jTree, org.w3c.dom.Document doc, TreeNode parentNode, String oldValue, String newValue) throws XPathExpressionException {
System.out.println("Selected path=" + jTree.getSelectionPath().toString());
boolean changed = false;
// Locate the node(s) with xpath
String[] pathTockens = jTree.getSelectionPath().toString().split(",");
StringBuilder sb = new StringBuilder();
//loop to construct xpath query
for (int i = 0; i < pathTockens.length - 1; i++) {
if (i == 0) {
//do nothing
} else if (i == 1) {
sb.append("/ns:" + pathTockens[i].trim());
} else if (i > 1 && i != pathTockens.length - 1) {
sb.append("/ns:" + pathTockens[i].trim());
} else {
//sb.append("/" + pathTockens[i].trim());
}
}//end loop
sb.append("[text()=");
sb.append("'");
sb.append(oldValue);
sb.append("']");
System.out.println("Constructed XPath Query:" + sb.toString());
//new xpath instance
XPathFactory xpathFactory = XPathFactory.newInstance();
XPath xpath = xpathFactory.newXPath();
xpath.setNamespaceContext(new UniversalNamespaceResolver(SingleTask.currentTask.getXsdFile().getXsdNameSpace()));
NodeList nodes = (NodeList) xpath.evaluate(sb.toString(), doc, XPathConstants.NODESET);
//start for
Node node;
String val = null;
for (int idx = 0; idx < nodes.getLength(); idx++) {
if (nodes.item(idx).getAttributes() != null) {
node = nodes.item(idx).getAttributes().getNamedItem("value");
if (node != null) {
val = node.getNodeValue();
node.setNodeValue(val.replaceAll(oldValue, newValue));
changed = true;
break;
}//end if node is found
}
}//end for
//set the new updated xml doc
SingleTask.currentTask.setDoc(doc);
return changed;
}
Class that implements custom namespace resolver:
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;
import org.w3c.dom.Document;
/**
*
* References:https://www.kdgregory.com/index.php?page=xml.xpath
*/
//custom NamespaceContext clss implementation
public class UniversalNamespaceResolver implements NamespaceContext
{
private String _prefix = "ns";
private String _namespaceUri=null;
private List<String> _prefixes = Arrays.asList(_prefix);
public UniversalNamespaceResolver(String namespaceResolver)
{
_namespaceUri = namespaceResolver;
}
#Override
#SuppressWarnings("rawtypes")
public Iterator getPrefixes(String uri)
{
if (uri == null)
throw new IllegalArgumentException("UniversalNamespaceResolver getPrefixes() URI may not be null");
else if (_namespaceUri.equals(uri))
return _prefixes.iterator();
else if (XMLConstants.XML_NS_URI.equals(uri))
return Arrays.asList(XMLConstants.XML_NS_PREFIX).iterator();
else if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(uri))
return Arrays.asList(XMLConstants.XMLNS_ATTRIBUTE).iterator();
else
return Collections.emptyList().iterator();
}
#Override
public String getPrefix(String uri)
{
if (uri == null)
throw new IllegalArgumentException("nsURI may not be null");
else if (_namespaceUri.equals(uri))
return _prefix;
else if (XMLConstants.XML_NS_URI.equals(uri))
return XMLConstants.XML_NS_PREFIX;
else if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(uri))
return XMLConstants.XMLNS_ATTRIBUTE;
else
return null;
}
#Override
public String getNamespaceURI(String prefix)
{
if (prefix == null)
throw new IllegalArgumentException("prefix may not be null");
else if (_prefix.equals(prefix))
return _namespaceUri;
else if (XMLConstants.XML_NS_PREFIX.equals(prefix))
return XMLConstants.XML_NS_URI;
else if (XMLConstants.XMLNS_ATTRIBUTE.equals(prefix))
return XMLConstants.XMLNS_ATTRIBUTE_NS_URI;
else
return null;
}
}
Console Output:
Selected path=[C:\Users\xyz\DocumentsIngest_LDD.xml, Ingest_LDD, Property_Maps, identifier, identifier1]
Constructed XPath: Query:/ns:Ingest_LDD/ns:Property_Maps/ns:identifier[text()='identifier1']
Attempt #4 (Without custom namespace resolver):
public boolean updateXmlData(JTree jTree, org.w3c.dom.Document doc, TreeNode parentNode, String oldValue, String newValue) throws XPathExpressionException {
System.out.println("Selected path=" + jTree.getSelectionPath().toString());
boolean changed = false;
// Locate the node(s) with xpath
String[] pathTockens = jTree.getSelectionPath().toString().split(",");
StringBuilder sb = new StringBuilder();
//loop to construct xpath query
for (int i = 0; i < pathTockens.length - 1; i++) {
if (i == 0) {
//do nothing
} else if (i == 1) {
sb.append("/" + pathTockens[i].trim());
} else if (i > 1 && i != pathTockens.length - 1) {
sb.append("/" + pathTockens[i].trim());
} else {
//sb.append("/" + pathTockens[i].trim());
}
}//end loop
sb.append("[text()=");
sb.append("'");
sb.append(oldValue);
sb.append("']");
System.out.println("Constructed XPath Query:" + sb.toString());
//new xpath instance
XPathFactory xpathFactory = XPathFactory.newInstance();
XPath xpath = xpathFactory.newXPath();
//WITHOUT CUSTOM NAMESPACE CONTEXT xpath.setNamespaceContext(new UniversalNamespaceResolver(SingleTask.currentTask.getXsdFile().getXsdNameSpace()));
NodeList nodes = (NodeList) xpath.evaluate(sb.toString(), doc, XPathConstants.NODESET);
//start for
Node node;
String val = null;
for (int idx = 0; idx < nodes.getLength(); idx++) {
if (nodes.item(idx).getAttributes() != null) {
node = nodes.item(idx).getAttributes().getNamedItem("value");
if (node != null) {
val = node.getNodeValue();
node.setNodeValue(val.replaceAll(oldValue, newValue));
changed = true;
break;
}//end if node is found
}
}//end for
//set the new updated xml doc
SingleTask.currentTask.setDoc(doc);
return changed;
}
Console Output:
Selected path=[C:\Users\anaim\Documents\XsdToXmlFiles\sampleIngest_LDD.xml, Ingest_LDD, Property_Maps, identifier, identifier1]
Constructed XPath Query:/Ingest_LDD/Property_Maps/identifier[text()='identifier1']
I actually manually wrote the XPath query online using (https://www.freeformatter.com/xpath-tester.html#ad-output)
Sorry, I cant provide the sample XMl, its way too large.
The manual XPath query was:
/Ingest_LDD/Property_Maps/identifier[text()='identifier1']
And the online tool successfully found the text & outputted:
Element='<identifier xmlns="http://pds.nasa.gov/pds4/pds/v1">identifier1</identifier>'
Therefore my code under attempt #4 & the query should work?
UPDATED ATTEMPTS AFTER USER INPUT:
Attempt #5 (based on response from user, namespace aware = TRUE ), relevant code is below
factory.setNamespaceAware(true);
doc = dBuilder.parse(xmlFile);
if (doc!=null)
{
//***NOTE program comes meaning doc is NOT null, however inspecting it shows [#document: null]
doc.getDocumentElement().normalize();
}
xpath.setNamespaceContext(new UniversalNamespaceResolver(SingleTask.currentTask.getXsdFile().getXsdNameSpace()));
Node node = (Node) xpath.evaluate(sb.toString(), doc, XPathConstants.NODE);
if (node!=null)
{
// See https://docs.oracle.com/javase/9/docs/api/org/w3c/dom/Node.html#setTextContent-java.lang.String-
node.setTextContent(newValue);
SingleTask.currentTask.setDoc(doc);
}
Output (again unable to find the node):
Selected path=[C:\Users\xyz\Documents\XsdToXmlFiles\sampleIngest_LDD.xml, Ingest_LDD, name, name1]
Constructed XPath Query:/Ingest_LDD/name[text()='name1']
Error changing value!
Attempt #6 (based on response from user, namespace aware = FALSE )
factory.setNamespaceAware(false);
doc = dBuilder.parse(xmlFile);
if (doc!=null)
{
//***NOTE program comes meaning doc is NOT null, however inspecting it shows [#document: null]
doc.getDocumentElement().normalize();
}
//COMMENTED OUT , SINCE NAMESPACE AWARE FALSE xpath.setNamespaceContext(new UniversalNamespaceResolver(SingleTask.currentTask.getXsdFile().getXsdNameSpace()));
Node node = (Node) xpath.evaluate(sb.toString(), doc, XPathConstants.NODE);
if (node!=null)
{
// See https://docs.oracle.com/javase/9/docs/api/org/w3c/dom/Node.html#setTextContent-java.lang.String-
node.setTextContent(newValue);
SingleTask.currentTask.setDoc(doc);
}
Output (again unable to find the node):
Selected path=[C:\Users\xyz\Documents\XsdToXmlFiles\sampleIngest_LDD.xml, Ingest_LDD, name, name1]
Constructed XPath Query:/Ingest_LDD/name[text()='name1']
Error changing value!
The document that is being returned as [#document: null] may not actually be the problem according to(DocumentBuilder.parse(InputStream) returns null)???
Attempt # 7 (namespace aware FALSE)
Also NamedNodeMap namedNodeMap = doc.getAttributes(); returns NULL.
However, Node firstChild = doc.getFirstChild() actually returns valid element!
I passed firstChild to xpath.evaluate(sb.toString(), firstChild , XPathConstants.NODE); but again the node desired node was not found.
Output (again unable to find the node):
Selected path=[C:\Users\xyz\Documents\XsdToXmlFiles\sampleIngest_LDD.xml, Ingest_LDD, name, name1]
Constructed XPath Query:/Ingest_LDD/name[text()='name1']
Error changing value!
Attempt # 8 (namespace aware false)
I also attemped to pass in doc.getChildNodes() to xpath.evaluate() rather than doc object as final desperate atteempt, see snippet below.
if (doc != null) {
NodeList nodes = (NodeList) xpath.evaluate(sb.toString(), doc.getChildNodes(), XPathConstants.NODESET);
String val = null;
Node node;
for (int idx = 0; idx < nodes.getLength(); idx++) {
if (nodes.item(idx).getAttributes() != null) {
node = nodes.item(idx).getAttributes().getNamedItem("value");
if (node != null) {
val = node.getNodeValue();
node.setNodeValue(val.replaceAll(oldValue, newValue));
changed = true;
break;
}//end if node is found
}
}//end for
}
Output (again unable to find the node):
Selected path=[C:\Users\xyz\Documents\XsdToXmlFiles\sampleIngest_LDD.xml, Ingest_LDD, name, name1]
Constructed XPath Query:/Ingest_LDD/name[text()='name1']
Error changing value!
For the test you performed online it seems your XML file contains namespace information.
With that information in mind, probably both of your examples of XPath evaluation would work, or not, dependent on several things.
For example, you probably can use the attempt #4, and the XPath evaluation will be adequate, if you are using a non namespace aware (the default) DocumentBuilderFactory and you o not provide any namespace information in your XPath expression.
But the XPath evaluation in attempt #3 can also be adequate if the inverse conditions apply, i.e., you are using a namespace aware DocumentBuilderFactory:
DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
f.setNamespaceAware(true);
and you provide namespace information in your XPath expression and a convenient NamespaceContext implementation. Please, see this related SO question and this great IBM article.
Be aware that you do not need to provide the same namespace prefixes in both your XML file an XPath expression, the only requirement is namespace awareness in XML (XPath is always namespace aware).
Given that conditions, I think you can apply both approaches.
In any case, I think the problem may have to do with the way you are dealing with the actual text replacement: you are looking for a node with a value attribute, and reviewing the associated XML Schema this attribute does not exist.
Please, consider instead the following approach:
// You can get here following both attempts #3 an #4
Node node = (Node) xpath.evaluate(sb.toString(), doc, XPathConstants.NODE);
boolean changed = node != null;
if (changed) {
// See https://docs.oracle.com/javase/9/docs/api/org/w3c/dom/Node.html#setTextContent-java.lang.String-
node.setTextContent(newValue);
SingleTask.currentTask.setDoc(doc);
}
return changed;
This code assumes that the selected node will be unique to work properly.
Although probably unlike, please, be aware that the way in which you are constructing the XPath selector from the JTree model can provide duplicates if you define the same value for repeated elements in your XML. Consider the elements external_id_property_maps in your screenshot, for instance.
In order to avoid that, you can take a different approach when constructing the XPath selector.
It is unclear for your code snippet, but probably you are using DefaultMutableTreeNode as the base JTree node type. If that is the case, you can associate with every node the arbitrary information you need to.
Consider for example the creation of a simple POJO with two fields, the name of the Element that the node represents, and some kind of unique, generated, id, let's name it uid or uuid to avoid confusion with the id attribute, most likely included in the original XML document.
This uid should be associated with every node. Maybe you can take advantage of the JTree creation process and, while processing every node of your XML file, include this attribute as well, generated using the UUID class, for example.
Or you can apply a XSLT transform to the original XML document prior to representation:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output method="xml" omit-xml-declaration="yes"/>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:attribute name="uid">
<xsl:value-of select="generate-id(.)"/>
</xsl:attribute>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
With this changes, your XPath query should looks like:
/ns:Ingest_LDD[#uid='w1ab1']/ns:Property_Maps[#uid='w1ab1a']/ns:identifier[#uid='w1ab1aq']
Of course, it will be necessary to modify the code devoted to the construction of this expression from the selected path of the JTree to take the custom object into account.
You can take this approach to the limit and use a single selector based solely in this uid attribute, although I think that for performance reasons it will be not appropriate:
//*[#uid='w1ab1']
Putting it all together, you can try something like the following.
Please, consider this XML file:
<?xml version="1.0" encoding="utf-8" ?>
<Ingest_LDD xmlns="http://pds.nasa.gov/pds4/pds/v1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://pds.nasa.gov/pds4/pds/v1 https://pds.nasa.gov/pds4/pds/v1/PDS4_PDS_1700.xsd">
<!-- Please, forgive me, I am aware that the document is not XML Schema conformant,
only for exemplification of the default namespace -->
<Property_Maps>
<identifier>identifier1</identifier>
</Property_Maps>
</Ingest_LDD>
First, let's parse the document:
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
// As the XML contains namespace, let's configure the parser namespace aware
// This will be of relevance when evaluating XPath
builderFactory.setNamespaceAware(true);
DocumentBuilder builder = builderFactory.newDocumentBuilder();
// Parse the document from some source
Document document = builder.parse(...);
// See http://stackoverflow.com/questions/13786607/normalization-in-dom-parsing-with-java-how-does-it-work
document.getDocumentElement().normalize();
Now, create a JTree structure corresponding to the input XML file. First, let's create a convenient POJO to store the required tree node information:
public class NodeInformation {
// Node name
private String name;
// Node uid
private String did;
// Node value
private String value;
// Setters and getters
// Will be reused by DefaultMutableTreeNode
#Override
public String toString() {
return this.name;
}
}
Convert the XML file to its JTree counterpart:
// Get a reference to root element
Element rootElement = document.getDocumentElement();
// Create root tree node
DefaultMutableTreeNode rootTreeNode = getNodeInformation(rootElement);
// Traverse DOM
traverse(rootTreeNode, rootElement);
// Create tree and tree model based on the computed root tree node
DefaultTreeModel treeModel = new DefaultTreeModel(rootTreeNode);
JTree tree = new JTree(treeModel);
Where:
private NodeInformation getNodeInformation(Node childElement) {
NodeInformation nodeInformation = new NodeInformation();
String name = childElement.getNodeName();
nodeInformation.setName(name);
// Provide a new unique identifier for every node
String uid = UUID.randomUUID().toString();
nodeInformation.setUid(uid);
// Uhnn.... We need to associate the new uid with the DOM node as well.
// There is nothing wrong with it but mutating the DOM in this way in
// a method that should be "read-only" is not the best solution.
// It would be interesting to study the above-mentioned XSLT approach
chilElement.setAttribute("uid", uid);
// Compute node value
StringBuffer buffer = new StringBuffer();
NodeList childNodes = childElement.getChildNodes();
boolean found = false;
for (int i = 0; i < childNodes.getLength(); i++) {
Node node = childNodes.item(i);
if (node.getNodeType() == Node.TEXT_NODE) {
String value = node.getNodeValue();
buffer.append(value);
found = true;
}
}
if (found) {
nodeInformation.setValue(buffer.toString());
}
}
And:
// Finds all the child elements and adds them to the parent node recursively
private void traverse(DefaultMutableTreeNode parentTreeNode, Node parentXMLElement) {
NodeList childElements = parentXMLElement.getChildNodes();
for(int i=0; i<childElements.getLength(); i++) {
Node childElement = childElements.item(i);
if (childElement.getNodeType() == Node.ELEMENT_NODE) {
DefaultMutableTreeNode childTreeNode =
new DefaultMutableTreeNode
(getNodeInformation(childElement));
parentTreeNode.add(childTreeNode);
traverse(childTreeNode, childElement);
}
}
}
Although the NamespaceContext implementation you provided looks fine, please, at a first step, try something simpler, to minimize the possibility of error. See the provided implementation below.
Then, your updateXMLData method should looks like:
public boolean updateXmlData(JTree tree, org.w3c.dom.Document doc, TreeNode parentNode, String oldValue, String newValue) throws XPathExpressionException {
boolean changed = false;
TreePath selectedPath = tree.getSelectionPath();
int count = getPathCount();
StringBuilder sb = new StringBuilder();
NodeInformation lastNodeInformation;
if (count > 0) {
for (int i = 1; i < trp.getPathCount(); i++) {
DefaultMutableTreeNode treeNode = (DefaultMutableTreeNode) trp.getPathComponent(i);
NodeInformation nodeInformation = (NodeInformation) treeNode.getUserObject();
sb.append(String.format("/ns:%s[#uid='%s']", nodeInformation.getName(), nodeInformation.getUid());
lastNodeInformation = nodeInformation;
}
}
System.out.println("Constructed XPath Query:" + sb.toString());
// Although the `NamespaceContext` implementation you provided looks
// fine, please, at a first step, try something simpler, to minimize the
// possibility of error. For example:
NamespaceContext nsContext = new NamespaceContext() {
public String getNamespaceURI(String prefix) {
if (prefix == null) {
throw new IllegalArgumentException("No prefix provided!");
} else if (prefix.equals(XMLConstants.DEFAULT_NS_PREFIX)) {
return "http://pds.nasa.gov/pds4/pds/v1";
} else if (prefix.equals("ns")) {
return "http://pds.nasa.gov/pds4/pds/v1";
} else {
return XMLConstants.NULL_NS_URI;
}
}
public String getPrefix(String namespaceURI) {
// Not needed in this context.
return null;
}
public Iterator getPrefixes(String namespaceURI) {
// Not needed in this context.
return null;
}
};
//new xpath instance
XPathFactory xpathFactory = XPathFactory.newInstance();
XPath xpath = xpathFactory.newXPath();
// As the parser is namespace aware, we can safely use XPath namespaces
xpath.setNamespaceContext(nsContext);
Node node = (Node) xpath.evaluate(sb.toString(), doc, XPathConstants.NODE);
boolean changed = node != null;
if (changed) {
// See https://docs.oracle.com/javase/9/docs/api/org/w3c/dom/Node.html#setTextContent-java.lang.String-
node.setTextContent(newValue);
SingleTask.currentTask.setDoc(doc);
// Probably the information has been updated in the node, but just in case:
lastNodeInformation.setValue(newValue);
}
return changed;
}
The generated XPath expression will look like:
/ns:Ingest_LDD[#uid='w1ab1']/ns:Property_Maps[#uid='w1ab1a']/ns:identifier[#uid='w1ab1aq']
If you want to use the default namespace, you can also try with:
/:Ingest_LDD[#uid='w1ab1']/:Property_Maps[#uid='w1ab1a']/:identifier[#uid='w1ab1aq']
Please, be aware that I haven't tested the code, but I hope you get the idea.
Just for clarification, in order to give you a proper answer, as mentioned before, if you now remove or comment this line of code:
builderFactory.setNamespaceAware(true);
Then, the XPath expression:
/ns:Ingest_LDD[#uid='w1ab1']/ns:Property_Maps[#uid='w1ab1a']/ns:identifier[#uid='w1ab1aq']
will no longer find the required node. Now, if you remove the namespace information from the XPath expression:
/Ingest_LDD[#uid='w1ab1']/Property_Maps[#uid='w1ab1a']/identifier[#uid='w1ab1aq']
It will find the right node again.
My aim is to make XML input, replace some text in node to XML DOM element and produce XML output. My XML input and expected output can be found here, in this SO question.
Here is my java code:
private static void textTransformCitations(Document document)
{
XPath xPath = XPathFactory.newInstance().newXPath();
String expression = "/article/body/sec/p/text()";
NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(document, XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); i++)
{
Node textNode = nodeList.item(i);
Matcher m = Pattern.compile("\\[(\\d+)\\]").matcher(textNode.getNodeValue());
while (m.find())
{
Text number = textNode.splitText(m.start(1));
textNode = number.splitText(m.group(1).length());
Element xref = document.createElement("xref");
xref.setAttribute("rid", "bib" + m.group(1));
xref.setAttribute("ref-type", "bibr");
number.getParentNode().replaceChild(number, xref);
xref.appendChild(number);
}
}
} // Added by edit!
Obviously the problem is that splitText() can be used only for Text interface:
textNode.splitText
which textNode variable is not. But I have explicitly stated to retrieve text from nodes with XPath.
What can I do to make this code working?
How can I use the splitText method in this case?
Change the statement Node textNode = nodeList.item(i); to Text textNode = (Text)nodelist.item(i);.
I need help in make an xpath expression to read all node names, node values, and attributes in an xml string. I made this:
private List<String> listOne = new ArrayList<String>();
private List<String> listTwo = new ArrayList<String>();
public void read(String xml) {
try {
// Turn String into a Document
Document document = DocumentBuilderFactory.newInstance()
.newDocumentBuilder().parse(new ByteArrayInputStream(xml.getBytes()));
// Setup XPath to retrieve all tags and values
XPath xPath = XPathFactory.newInstance().newXPath();
NodeList nodeList = (NodeList) xPath.evaluate("//text()[normalize-space()='']", document, XPathConstants.NODESET);
// Iterate through nodes
for(int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i);
listOne.add(node.getNodeName());
listTwo.add(node.getNodeValue());
// Another list to hold attributes
}
} catch(Exception e) {
LogHandle.info(e.getMessage());
}
}
I found the expression //text()[normalize-space()=''] online; however, it doesn't work. When I get try to get the node name from listOne, it is just #text. I tried //, but that doesn't work either. If I had this XML:
<Data xmlns="Somenamespace.nsc">
<Test>blah</Test>
<Foo>bar</Foo>
<Date id="2">12242016</Date>
<Phone>
<Home>5555555555</Home>
<Mobile>5555556789</Mobile>
</Phone>
</Data>
listOne[0] should hold Data, listOne[1] should hold Test, listTwo[1] should hold blah, etc... All the attributes will be saved in another parallel list.
What expression should xPath evaluate?
Note: The XML String can have different tags, so I can't hard code anything.
Update: Tried this loop:
NodeList nodeList = (NodeList) xPath.evaluate("//*", document, XPathConstants.NODESET);
// Iterate through nodes
for(int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i);
listOne.add(i, node.getNodeName());
// If null then must be text node
if(node.getChildNodes() == null)
listTwo.add(i, node.getTextContent());
}
However, this only gets the root element Data, then just stops.
//* will select all element nodes, //#* all attribute nodes. However, an element node does not have a meaningful node value in the DOM, so you would need to read out getTextContent() instead of getNodeValue.
As you seem to consider an element with child elements to have a "null" value I think you need to check whether there are any child elements:
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
docBuilderFactory.setNamespaceAware(true);
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse("sampleInput1.xml");
XPathFactory fact = XPathFactory.newInstance();
XPath xpath = fact.newXPath();
NodeList allElements = (NodeList)xpath.evaluate("//*", doc, XPathConstants.NODESET);
ArrayList<String> elementNames = new ArrayList<>();
ArrayList<String> elementValues = new ArrayList<>();
for (int i = 0; i < allElements.getLength(); i++)
{
Node currentElement = allElements.item(i);
elementNames.add(i, currentElement.getLocalName());
elementValues.add(i, xpath.evaluate("*", currentElement, XPathConstants.NODE) != null ? null : currentElement.getTextContent());
}
for (int i = 0; i < elementNames.size(); i++)
{
System.out.println("Name: " + elementNames.get(i) + "; value: " + (elementValues.get(i)));
}
For the sample input
<Data xmlns="Somenamespace.nsc">
<Test>blah</Test>
<Foo>bar</Foo>
<Date id="2">12242016</Date>
<Phone>
<Home>5555555555</Home>
<Mobile>5555556789</Mobile>
</Phone>
</Data>
the output is
Name: Data; value: null
Name: Test; value: blah
Name: Foo; value: bar
Name: Date; value: 12242016
Name: Phone; value: null
Name: Home; value: 5555555555
Name: Mobile; value: 5555556789
im struggling with extracting value from a specific node in my XML document. Im using w3c.DOM as i have found many tutorials on it but now i cant find any good ones for this task - i had to use XPath for this task instead.
I always know the exact path (and passing it as a string, example: "Car/Wheels/Wheel[#Index=´x´]/" ) leading to a node from which i need to extract a value (a string) and return it (im converting the string into doubles and integers in other methods later). Variable myDoc is Document myDoc.
How do i get this value?
private String xPathValue(String path){
XPath myPath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xpath.compile(path);
String result = (String)expr.evaluate(myDoc);
return result;
}
This however doesnt work and i dont want to create any NodeList since i know the exact paths. Im looking for something that works like Node.getTextContent();
You have 2 options
1) Alter you xPath to return the value of the node instead of the node itself
Using expression: Car/Wheels/Wheel[#Index=´x´]/text()
private String xPathValue(String path) {
XPath myPath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xpath.compile(path);
String result = (String)expr.evaluate(myDoc, XPathConstants.STRING);
return result;
}
2) Use the same xpath query but return a node type
Using expression: Car/Wheels/Wheel[#Index=´x´]
private String xPathValue(String path) {
XPath myPath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xpath.compile(path);
Node result = (Node)expr.evaluate(myDoc, XPathConstants.NODE);
return result.getTextContent();
}
<subjectOf typeCode="SUBJ">
<annotation classCode="ACT" moodCode="EVN">
<realmCode code="QD" />
<code code="SPECIALNOTE"></code>
<text><![CDATA[<strong>** New York State approval pending. This test is not available for New York State patient testing **</br> ]]></text>
</annotation>
</subjectOf>
<subjectOf typeCode="SUBJ">
<annotation classCode="ACT" moodCode="EVN">
<realmCode code="QD" />
<code code="PREFERREDSPECIMEN"></code>
<text><![CDATA[2 mL Second void urine <strong>or </strong>2-hour urine <strong>or </strong> 2 mL Urine with no preservative]]></text>
</annotation>
</subjectOf>
In DOM parsing, how can I traverse through the above XML and get the <text> tag value depending upon a <code> tag attribute having a given value. For example, I want to get the following text:
<strong>** New York State approval pending. This test is not available
for New York State patient testing **</br>
...based on the <code> tag with a code attribute where value="SPECIALNOTE".
public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {
DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
DocumentBuilder builder = domFactory.newDocumentBuilder();
Document doc = builder.parse("xml.xml");
XPath xpath = XPathFactory.newInstance().newXPath(); // XPath Query for showing all nodes value
XPathExpression expr = xpath.compile("/testCodeIdentifier/subjectOf/subjectOf/annotation/code[#code='SPECIALNOTE']");
Object result = expr.evaluate(doc, XPathConstants.NODESET);
NodeList nodes = (NodeList) result;
for (int i = 0; i < nodes.getLength(); i++) {
System.out.println("........"+nodes.item(i).getNodeValue()+"........");
}
}
}
Appreciate the help in advance...
First, your XPath expression has an error; subjectOf is repeated unnecessarily:
/subjectOf/subjectOf
Now, assuming you really do need a reference to the code node that precedes the target text element, then use the following:
XPathExpression expr = xpath.compile(
"/testCodeIdentifier/subjectOf/annotation/code[#code='SPECIALNOTE']");
Node node = (Node) expr.evaluate(doc, XPathConstants.NODE);
System.out.println(getNextElementSibling(node).getTextContent());
Where getNextElementSibling is defined as follows:
public static Node getNextElementSibling(Node node) {
Node next = node;
do {
next = next.getNextSibling();
} while ((next != null) && (next.getNodeType() != Node.ELEMENT_NODE));
return next;
}
A couple of notes about this:
The reason that getNextSibling did not originally work for you is (most likely) because the next sibling of the referenced code element is a text node, not an element node. (The whitespace between code and text is significant.) That's why we need getNextElementSibling.
We're selecting a single node, so we're using XPathConstants.NODE instead if XPathConstants.NODELIST
Note that you should probably just do as #Lukas suggests and modify your XPath expression to directly select the target text.
Here's how to get the text directly (as a String):
XPathExpression expr = xpath.compile(
"/testCodeIdentifier/subjectOf/annotation[code/#code='SPECIALNOTE']/text/text()");
String text = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println(text);
Here's how to first get a reference to the element and then retrieve the contents of its CDATA section:
XPathExpression expr = xpath.compile(
"/testCodeIdentifier/subjectOf/annotation[code/#code='SPECIALNOTE']/text");
Node text = (Node) expr.evaluate(doc, XPathConstants.NODE);
System.out.println(text.getTextContent());
Fix your XPath expression like this:
/testCodeIdentifier/subjectOf/annotation[code/#code='SPECIALNOTE']/text
You could then, for instance, access the CDATA content using
Node.getTextContent();
UPDATE: The above XPath seemed correct at the time I posted it. In the meantime, you have completely changed your XML code and now, the XPath would read
/testCodeIdentifier/subjectOf/code/subjectOf/annotation[code/#code='SPECIALNOTE']/text
Or, because I am guessing that this question is so messy, it's still wrong, just do:
//annotation[code/#code='SPECIALNOTE']/text
Finally i have got the answer for my question by myself.... Below code is being working for my XML to be parsed...
XPath xpath = XPathFactory.newInstance().newXPath();
// XPath Query for showing all nodes value
XPathExpression expr = xpath.compile("//testCodeIdentifier/subjectOf/order/subjectOf/annotation/code[#code='SPECIALNOTE']/following-sibling::text/text()");
Object result = expr.evaluate(doc, XPathConstants.NODESET);
NodeList nodes = (NodeList) result;
for (int i = 0; i < nodes.getLength(); i++) {
System.out.println(nodes.item(i).getNodeValue());
}
Thank you people who have ansewered in this post but this is a possible solution for it. Have a mark on it.