Develop Reference

How to extract one boolean field from XML?

I have a model which is in XML format as shown below and I need to parse the XML and check whether my XML has internal-flag flag set as true or not. In my other models, it might be possible, that internal-flag flag is set as false. And sometimes, it is also possible that this field won't be there so by default it will be false from my code.
<?xml version="1.0"?>
<ClientMetadata
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.google.com client.xsd"
xmlns="http://www.google.com">
<client id="200" version="13">
<name>hello world</name>
<description>hello hello</description>
<organization>TESTER</organization>
<author>david</author>
<internal-flag>true</internal-flag>
<clock>
<clock>
<for>
<init>val(tmp1) = 1</init>
<clock>
<eval><![CDATA[result("," + $convert(val(tmp1)))]]></eval>
</clock>
</for>
<for>
<incr>val(tmp1) -= 1</incr>
<clock>
<eval><![CDATA[result("," + $convert(val(tmp1)))]]></eval>
</clock>
</for>
</clock>
</clock>
</client>
</ClientMetadata>
I have a POJO in which I am storing my above model -
public class ModelMetadata {
private int modelId;
private String modelValue; // this string will have my above XML data as string
// setters and getters here
}
Now what is the best way to determine whether my model has internal-flag set as true or not?
// this list will have all my Models stored
List<ModelMetadata> metadata = getModelMetadata();
for (ModelMetadata model : metadata) {
// my model will be stored in below variable in XML format
String modelValue = model.getModelValue();
// now parse modelValue variable and extract `internal-flag` field property
}
Do I need to use XML parsing for this or is there any better way to do this?
Update:-
I have started using Stax and this is what I have tried so far but not sure how can I extract that field -
InputStream is = new ByteArrayInputStream(modelValue.getBytes());
XMLStreamReader r = XMLInputFactory.newInstance().createXMLStreamReader(is);
while(r.hasNext()) {
// now what should I do here?
}

There is an easy solution using XMLBeam (Disclosure: I'm affiliated with that project), just a few lines:
public class ReadBoolean {
public interface ClientMetaData {
#XBRead("//xbdefaultns:internal-flag")
boolean hasFlag();
}
public static void main(String[] args) throws IOException {
ClientMetaData clientMetaData = new XBProjector().io().url("res://xmlWithBoolean.xml").read(ClientMetaData.class);
System.out.println("Has flag:"+clientMetaData.hasFlag());
}
}
This program prints out
Has flag:true
for your XML.

You could also do some simple string parsing, but this will only work for small cases with proper XML and if there's only a single <internal-flag> element.
This is a simple solution to your problem without using any XML parsing utilities. Other solutions may be more robust or powerful.
Find the index of the string literal <internal-flag>. If it doesn't exist, return false.
Go forward "<internal-flag>".length (15) characters. Read up to the next </internal-flag>, which should be the string true or false.
Take that string, use Boolean.parseBoolean(String) to get a boolean value.
If you want me to help you out with the code just drop a comment!

If you are willing to consider adding Groovy to your mix (e.g. see the book Making Java Groovy) then using a Groovy XMLParser and associated classes will make this simple.
If you need to stick to Java, let me put in a shameless plug for my Xen library, which mimics a lot of the "Groovy way". The answer to your question would be:
Xen doc = new XenParser().parseText(YOUR_XML_STRING);
String internalFlag = doc.getText(".client.internal-flag");
boolean isSet = "true".equals(internalFlag);
If the XML comes from a File, Stream, or URI, that can be handled too.
Caveat emptor, (even though it is free) this is a fairly new library, written solely by a random person (me), and not thoroughly tested on all the crazy XML out there. If anybody knows of a similar, more "mainstream" library I'd be very interested in hearing about it.

How to extract xml tag value without using the tag name in java?

I am using java.I have an xml file which looks like this:
<?xml version="1.0"?>
<personaldetails>
<phno>1553294232</phno>
<email>
<official>xya#gmail.com</official>
<personal>bk#yahoo.com</personal>
</email>
</personaldetails>
Now,I need to check each of the tag values for its type using specific conditions,and put them in separate files.
For example,in the above file,i write conditions like 10 digits equals phone number,
something in the format of xxx#yy.com is an email..
So,what i need to do is i need to extract the tag values in each tag and if it matches a certain condition,it is put in the first text file,if not in the second text file.
in that case,the first text file will contain:
1553294232
xya#gmail.com
bk#yahoo.com
and the rest of the values in the second file.
i just don't know how to extract the tag values without using the tag name.(or without using GetElementsByTagName).
i mean this code should extract the email bk#yahoo.com even if i give <mailing> instead of <personal> tag.It should not depend on the tag name.
Hope i am not confusing.I am new to java using xml.So,pardon me if my question is silly.
Please Help.

Seems like a typical use case for XPath
XPath allows you to query XML in a very flexible way.
This tutorial could help:
http://www.javabeat.net/2009/03/how-to-query-xml-using-xpath/
If you're using Java script, which could to be the case, since you mention getElementsByTagName(), you could just use JQuery selectors, it will give you a consistent behavior across browsers, and JQuery library is useful for a lot of other things, if you are not using it already... http://api.jquery.com/category/selectors/
Here for example is information on this:
http://www.switchonthecode.com/tutorials/xml-parsing-with-jquery

Since you don't know your element name, I would suggest creating a DOM tree and iterating through it. As and when you get a element, you would try to match it against your ruleset (and I would suggest using regex for this purpose) and then write it to your a file.
This would be a sample structure to help you get started, but you would need to modify it based on your requirement:
public void parseXML(){
try{
DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc;
doc = documentBuilder.parse(new File("test.xml"));
getData(null, doc.getDocumentElement());
}catch(Exception exe){
exe.printStackTrace();
}
}
private void getData(Node parentNode, Node node){
switch(node.getNodeType()){
case Node.ELEMENT_NODE:{
if(node.hasChildNodes()){
NodeList list = node.getChildNodes();
int size = list.getLength();
for(int index = 0; index < size; index++){
getData(node, list.item(index));
}
}
break;
}
case Node.TEXT_NODE:{
String data = node.getNodeValue();
if(data.trim().length() > 0){
/*
* Here you need to check the data against your ruleset and perform your operation
*/
System.out.println(parentNode.getNodeName()+" :: "+node.getNodeValue());
}
break;
}
}
}
You might want to look at the Chain of Responsibility design pattern to design your ruleset.

extracting xml node(not text but complete xml ) and with other test nodes from xml file using SAX parser in java

I have to read from large xml files each ranging ~500MB. The batch processes typically 500 such files in each run. I have to extract text nodes from it and at the same time extract xml nodes from it. I used xpath DOM in java for easy of use but that doesn't work due to memory issues as i have limited resources.
I intent to use SAX or stax in java now - the text nodes can be easily extracted but i don't know how to extract xml nodes from xml using sax.
a sample:
<?xml version="1.0"?>
<Library>
<Book name = "ABC">
<Author>John</Author>
<PrintingCompanyDT><Printer>Sam</Printer><Printmachine>Laser</Printmachine>
<AssocPrint>Oreilly</AssocPrint> </PrintingCompanyDT>
</Book>
<Book name = "123">
<Author>Mason</Author>
<PrintingCompanyDTv<Printervkelly</Printer><Printmachine>DOTPrint</Printmachine>
<AssocPrint>Oxford</AssocPrint> </PrintingCompanyDT>
</Book>
</Library>
The expected result:
1)Book: ABC:
Author:John
PrintCompany Detail XML:
<PrintingCompanyDT>
<Printer>Sam</Printer>
<Printmachine>Laser</Printmachine>
<AssocPrint>Oreilly</AssocPrint>
</PrintingCompanyDT>
2) Book: 123
Author : Mason
PrintCompany Detail XML:
<PrintingCompanyDT>
<Printer>kelly</Printer>
<Printmachine>DOTPrint</Printmachine>
<AssocPrint>Oxford</AssocPrint>
</PrintingCompanyDT>
If i try in the regular way of appending characters in public void characters(char ch[], int start, int length) method
I get the below
1)Book: ABC:
Author:John
PrintCompany Detail XML :
Sam
Laser
Oreilly
exactly the content and spaces.
Can somebody suggest how to extract an xml node as it is from a xml file through SAX or StaX parser in java.

I'd be tempted to use XOM for this sort of task rather than SAX or StAX directly. XOM is a tree-based representation similar to DOM or JDOM but it has support for processing XML "twigs" in a kind of semi-streaming fashion, ideal for your kind of case where you have many similar elements that can be processed independently of one another. Also every Node has a toXML method that prints the node as XML.
import nu.xom.*;
public class LibraryProcessor extends NodeFactory {
private Nodes empty = new Nodes();
private bookNum = 0;
/** Called for each closing tag in the XML */
public Nodes finishMakingElement(Element element) {
if("Book".equals(element.getLocalName())) {
bookNum++;
// process the complete Book element ...
processBook(element);
// ... and throw it away
return empty;
} else {
// process other elements (except Book) in the normal way
return super.finishMakingElement(element);
}
}
private void processBook(Element book) {
System.out.println(bookNum + ": " +
book.getAttributeValue("name"));
System.out.println("Author: " +
book.getFirstChildElement("Author").getValue());
System.out.println("PrintCompany Detail XML: " +
book.getFirstChildElement("PrintingCompanyDT").toXML());
}
public static void main(String[] args) throws Exception {
Builder builder = new Builder(new LibraryProcessor());
builder.build(new File(args[0]));
}
}
This will work its way through the XML document, calling processBook once for each Book element in turn. Within processBook you have access to the whole Book XML tree as XOM nodes, but without having to load the entire file into memory in one go - the best of both worlds. The "Factories, Filters, Subclassing, and Streaming" section of the XOM tutorial has more detail on this technique.
This example just shows the most basic bits of the XOM API, but it also provides powerful XPath support if you need to do more complex processing. For example, you can directly access the PrintMachine element within processBook using
Element machine = (Element)book.query("PrintingCompanyDT/PrintMachine").get(0);
or if the structure is not so regular, for example if PrintingCompanyDT is sometimes a direct child of Book and sometimes deeper (e.g. a grandchild) then you can use a query like
Element printingCompanyDT = (Element)book.query(".//PrintingCompanyDT").get(0);
(// being the XPath notation for finding descendants at any level, as opposed to / which looks only for direct children).

best java Xml parser to manipulate/edit an existing xml document

TASK : I have an existing xml document (UTF-8) which uses xml namespaces and xml schema. I need to parse to a particular element, append content (that also needs to use xml namespace prefixes) to this element and then write out the Document again.
which is the best XML parser library that I should be using for this TASK ?
I've seen a previous thread (Best XML parser for Java) but was not sure if dom4j or JDOM is any good for namespaces/xmlSchema and good support for UTF-8 characters.
Some parsers that seems like a task for
JDom
Dom4J
XOM
WoodStock
Any idea which one is the best ? :-) I use JDK 6 and would prefer NOT to use the built-in SAX/DOM facilities to do this job because that requires me to write too much code.
Would help to have some examples of doing such a task.

Using JDOM, taking an InputStream and making it a Document:
InputStream inputStream = (InputStream)httpURLConnection.getContent();
DocumentBuilderFactory docbf = DocumentBuilderFactory.newInstance();
docbf.setNamespaceAware(true);
DocumentBuilder docbuilder = docbf.newDocumentBuilder();
Document document = docbuilder.parse(inputStream, baseUrl);
At that point, you have the XML in a Java object. Done. Easy.
You can either use the document object and the Java API to just walk through it, or also use XPath, which I find easier (once I learned it).
Build an XPath object, which takes a bit:
public static XPath buildXPath() {
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
xpath.setNamespaceContext(new AtomNamespaceContext());
return xpath;
}
public class AtomNamespaceContext implements NamespaceContext {
public String getNamespaceURI(String prefix) {
if (prefix == null)
throw new NullPointerException("Null prefix");
else if ("a".equals(prefix))
return "http://www.w3.org/2005/Atom";
else if ("app".equals(prefix))
return "http://www.w3.org/2007/app";
else if ("os".equals(prefix))
return "http://a9.com/-/spec/opensearch/1.1/";
else if ("x".equals(prefix))
return "http://www.w3.org/1999/xhtml";
else if ("xml".equals(prefix))
return XMLConstants.XML_NS_URI;
return XMLConstants.NULL_NS_URI;
}
// This method isn't necessary for XPath processing.
public String getPrefix(String uri) {
throw new UnsupportedOperationException();
}
// This method isn't necessary for XPath processing either.
public Iterator getPrefixes(String uri) {
throw new UnsupportedOperationException();
}
}
Then just use it, which (thankfully) doesn't take much time at all:
return Integer.parseInt(xpath.evaluate("/a:feed/os:totalResults/text()", document));

Use XSLT. Seriously. This is a perfect job for it. Just use a copy template to copy everything as is except for the place where you need to add more xml. You can even add the XML by actually writing XML instead of DOM manipulation.
This is the copy template:
<xsl:template match="node() | #*">
<xsl:copy>
<xsl:apply-templates select="#* | node()"/>
</xsl:copy>
</xsl:template>
I know a lot of people hate XSLT, but this is a task where it would really shine and take almost no code. Also, you could just use what's in the JDK.

Since writing too much code is the main issue for you, you might want to consider jOOX:
http://code.google.com/p/joox/
I have created jOOX to be a port of jQuery to Java. The underlying technology is Java's standard DOM. Some sample code:
// Find the order at index for and add an element "paid"
$(document).find("orders").children().eq(4)
.append("<paid>true</paid>");
// Find those orders that are paid and flag them as "settled"
$(document).find("orders").children().find("paid")
.after("<settled>true</settled>");
// Add a complex element
$(document).find("orders").append(
$("order", $("date", "2011-08-14"),
$("amount", "155"),
$("paid", "false"),
$("settled", "false")).attr("id", "13");
Note: Namespaces are not yet explicitly supported, but you can work around that

It sounds like you can write an xslt style sheet to do what you want.

Saxon 8 (Java version) problem

I'll point out now, that I'm new to using saxon, and I've tried following the docs and examples in the package, but I'm just not having luck with this problem.
Basically, I'm trying to do some xml processing in java using saxon v8. In order to get something working, I took one of the sample files included in the package and modified to my needs. It works so long as I'm not using namespaces, and that is my question. How can I get around the namespace problem? I don't really care to use it, but it exists in my xml, so I either have to use it or ignore it. Either solution is fine.
Anyway, here is my starter code. It doesn't do anything but take an xpath query try to use it against the hard coded xml doc.
public static void main(String[] args) {
String query = args[0];
File XMLStream=null;
String xmlFileName="doc.xml";
OutputStream destStream=System.out;
XQueryExpression exp=null;
Configuration C=new Configuration();
C.setSchemaValidation(false);
C.setValidation(false);
StaticQueryContext SQC=new StaticQueryContext(C);
DynamicQueryContext DQC=new DynamicQueryContext(C);
QueryProcessor processor = new QueryProcessor(SQC);
Properties props=new Properties();
try{
exp=processor.compileQuery(query);
XMLStream=new File(xmlFileName);
InputSource XMLSource=new InputSource(XMLStream.toURI().toString());
SAXSource SAXs=new SAXSource(XMLSource);
DocumentInfo DI=SQC.buildDocument(SAXs);
DQC.setContextNode(DI);
SequenceIterator iter = exp.iterator(DQC);
while(true){
Item i = iter.next();
if(i != null){
System.out.println(i.getStringValue());
}
else break;
}
}
catch (Exception e){
System.err.println(e.getMessage());
}
}
An example XML file is here...
<?xml version="1.0"?>
<ns1:animal xmlns:ns1="http://my.catservice.org/">
<cat>
<catId>8889</catId>
<fedStatus>true</fedStatus>
</cat>
</ns1:animal>
If I run this with a query including the namespace, I get an error. For example:
/ns1:animal/cat/ gives the error: "Prefix ns1 has not been declared".
If I remove the ns1: from the query, it gives me nothing. If I doctor the xml to remove the "ns1:" prepended to "animal" I can run the query /animal/cat/ with success.
Any help would be greatly appreciated. Thanks.

Error message correctly points out that your xpath expression does not indicate what namespace prefix "ns1" means (binds to). Just because document to operate on happens to use binding for "ns1" does not mean it is what should be used: this because in XML, it's the namespace URI that matters, and prefixes are just convenient shortcuts to the real thing.
So: how do you define the binding? There are 2 generic ways; either provide a context that can resolve the prefix, or embed actual URI within XPath expression.
Regarding the first approach, this email from Saxon author mentions JAXP method XPath.setNamespaceContext(), similarly, Jaxen XPath processor FAQ has some sample code that could help
That's not very convenient, as you have to implement NamespaceContext, but once you have an implementation you'll be set.
So the notation approach... let's see: Top Ten Tips to Using XPath and XPointer shows this example:
to match element declared with namespace like:
xmlns:book="http://my.example.org/namespaces/book"
you use XPath name like:
{http://my.example.org/namespaces/book}section
which hopefully is understood by Saxon (or Jaxen).
Finally, I would recommend upgrading to Saxon9 if possible, if you have any trouble using one of above solutions.

If you want to have something working out of the box, you can check out embedding-xquery-in-java. There's github project, which uses Saxon to evaluate some sample XQuery expressions.
Regards