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How to parse XML in java to save values in db using STAX?

I am new to JAVA STAX Parser and I have to parse a xml to populate my database table.
While trying to read XML file using STAX I came across this problem.
In an XML file, I may have child nodes with the same name in different root nodes. I couldn't quite figure out how to read specific child nodes from root nodes.
XML File Sample:-
<?xml version="1.0" encoding="UTF-8"?>
<DOC xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="XML.xsd">
<FMTR>
<TITLEPG>
<TITLENUM>Title 1</TITLENUM>
<SUBJECT>Test 1</SUBJECT>
</TITLEPG>
<BTITLE>
<P></P>
</BTITLE>
<TOC>
<EXPL>
<SUBJECT>Explanation</SUBJECT>
</EXPL>
<TITLENO>
<CHAPTI>
<SUBJECT>Chapter I—Test 1</SUBJECT>
</CHAPTI>
</TITLENO>
<FAIDS>
<SUBJECT>Table of Titles and Chapters</SUBJECT>
<SUBJECT>Alphabetical List</SUBJECT>
</FAIDS>
</TOC>
</FMTR>
</DOC>
For eg:- I have to read the SUBJECT tag of TITLEPG root tag and populate the database table accordingly.
Can we get the child nodes of a root node using STAX?
What is the best approach to do parse it: STAX or JDOM?

The XMLEventReader class in Java StAX is an Iterator based API for reading XML files. It will let you move from event to event in the XML, allowing you to decide when to move to the next event.
You are looking for "events" here. pls bear in mind Stax and xpath are very different things. Stax allows you to parse a streaming XML document in a forward direction only.
You can create an XMLEventReader via the javax.xml.stream.XMLInputFactory class. Try running demo code ( make changes as required) and you can see the object you want.
XMLInputFactory factory = XMLInputFactory.newInstance();
//get Reader connected to XML input from somewhere..
Reader reader = getXmlReader();
try {
XMLEventReader eventReader =
factory.createXMLEventReader(reader);
} catch (XMLStreamException e) {
e.printStackTrace();
}
Now play around with this eventReader to get you what you want...iterate over it, see in debug mode,
while(eventReader.hasNext()){
// this is what you want...
XMLEvent event = eventReader.nextEvent();
if(event.getEventType() == XMLStreamConstants.START_ELEMENT){
StartElement startElement = event.asStartElement();
System.out.println(startElement.getName().getLocalPart());
}
//handle more event types here...
}

How to modify a huge XML file by StAX?

I have a huge XML (~2GB) and I need to add new Elements and modify the old ones. For example, I have:
<books>
<book>....</book>
...
<book>....</book>
</books>
And want to get:
<books>
<book>
<index></index>
....
</book>
...
<book>
<index></index>
....
</book>
</books>
I used the following code:
XMLInputFactory inFactory = XMLInputFactory.newInstance();
XMLEventReader eventReader = inFactory.createXMLEventReader(new FileInputStream(file));
XMLOutputFactory factory = XMLOutputFactory.newInstance();
XMLStreamWriter writer = factory.createXMLStreamWriter(new FileWriter(file, true));
while (eventReader.hasNext()) {
XMLEvent event = eventReader.nextEvent();
if (event.getEventType() == XMLEvent.START_ELEMENT) {
if (event.asStartElement().getName().toString().equalsIgnoreCase("book")) {
writer.writeStartElement("index");
writer.writeEndElement();
}
}
}
writer.close();
But the result was the following:
<books>
<book>....</book>
....
<book>....</book>
</books><index></index>
Any ideas?

Try this
XMLInputFactory inFactory = XMLInputFactory.newInstance();
XMLEventReader eventReader = inFactory.createXMLEventReader(new FileInputStream("1.xml"));
XMLOutputFactory factory = XMLOutputFactory.newInstance();
XMLEventWriter writer = factory.createXMLEventWriter(new FileWriter(file));
XMLEventFactory eventFactory = XMLEventFactory.newInstance();
while (eventReader.hasNext()) {
XMLEvent event = eventReader.nextEvent();
writer.add(event);
if (event.getEventType() == XMLEvent.START_ELEMENT) {
if (event.asStartElement().getName().toString().equalsIgnoreCase("book")) {
writer.add(eventFactory.createStartElement("", null, "index"));
writer.add(eventFactory.createEndElement("", null, "index"));
}
}
}
writer.close();
Notes
new FileWriter(file, true) is appending to the end of the file, you hardly really need it
equalsIgnoreCase("book") is bad idea because XML is case-sensitive

Well it is pretty clear why it behaves the way it does. What you are actually doing is opening the existing file in output append mode and writing elements at the end. That clearly contradicts what you are trying to do.
(Aside: I'm surprised that it works as well as it does given that the input side is likely to see the elements that the output side is added to the end of the file. And indeed the exceptions like Evgeniy Dorofeev's example gives are the sort of thing I'd expect. The problem is that if you attempt to read and write a text file at the same time, and either the reader or writer uses any form of buffering, explicit or implicit, the reader is liable to see partial states.)
To fix this you have to start by reading from one file and writing to a different file. Appending won't work. Then you have to arrange that the elements, attributes, content etc that are read from the input file are copied to the output file. Finally, you need to add the extra elements at the appropriate points.
And is there any possibility to open the XML file in mode like RandomAccessFile, but write in it by StAX methods?
No. That is theoretically impossible. In order to to be able to navigate around an XML file's structure in a "random" file, you'd first need to parse the whole thing and build an index of where all the elements are. Even when you've done that, the XML is still stored as characters in a file, and random access does not allow you to insert and remove characters in the middle of a file.
Maybe your best bet would be combining XSL and a SAX style parser; e.g. something along the lines of this IBM article: http://ibm.com/developerworks/xml/library/x-tiptrax

Maybe this StAX Read-and-Write Example in JavaEE tutorial helps: http://docs.oracle.com/javaee/5/tutorial/doc/bnbfl.html#bnbgq
You can download the tutorial examples here: https://java.net/projects/javaeetutorial/downloads

Parse a list of XML fragments with no root element from a stream input

Is it feasible in Java using the SAX api to parse a list of XML fragments with no root element from a stream input?
I tried parsing such an XML but got a
org.xml.sax.SAXParseException: The markup in the document following the root element must be well-formed.
before even the endDocument event was fired.
I would like not to settle with obvious but clumsy solutions as "Pre-append a custom root element or Use buffered fragment parsing".
I am using the standard SAX API of Java 1.6. The SAX factory had setValidating(false) in case anyone wondered.

First, and most important of all, the content you are parsing is not an XML document.
From the XML Specification:
[Definition: There is exactly one element, called the root, or document element, no part of which appears in the content of any other element.]
Now, as to parsing this with SAX - in spite of what you said about clumsiness - I'd suggest the following approach:
Enumeration<InputStream> streams = Collections.enumeration(
Arrays.asList(new InputStream[] {
new ByteArrayInputStream("<root>".getBytes()),
yourXmlLikeStream,
new ByteArrayInputStream("</root>".getBytes()),
}));
SequenceInputStream seqStream = new SequenceInputStream(streams);
// Now pass the `seqStream` into the SAX parser.
Using the SequenceInputStream is a convenient way of concatenating multiple input streams into a single stream. They will be read in the order they are passed to the constructor (or in this case - returned by the Enumeration).
Pass it to your SAX parser, and you are done.

How to create XML file?

I have some data which my program discovers after observing a few things about files.
For instance, i know file name, time file was last changed, whether file is binary or ascii text, file content (assuming it is properties) and some other stuff.
i would like to store this data in XML format.
How would you go about doing it?
Please provide example.

If you want something quick and relatively painless, use XStream, which lets you serialise Java Objects to and from XML. The tutorial contains some quick examples.

Use StAX; it's so much easier than SAX or DOM to write an XML file (DOM is probably the easiest to read an XML file but requires you to have the whole thing in memory), and is built into Java SE 6.
A good demo is found here on p.2:
OutputStream out = new FileOutputStream("data.xml");
XMLOutputFactory factory = XMLOutputFactory.newInstance();
XMLStreamWriter writer = factory.createXMLStreamWriter(out);
writer.writeStartDocument("ISO-8859-1", "1.0");
writer.writeStartElement("greeting");
writer.writeAttribute("id", "g1");
writer.writeCharacters("Hello StAX");
writer.writeEndDocument();
writer.flush();
writer.close();
out.close();

Standard are the W3C libraries.
final Document docToSave = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
final Element fileInfo = docToSave.createElement("fileInfo");
docToSave.appendChild(fileInfo);
final Element fileName = docToSave.createElement("fileName");
fileName.setNodeValue("filename.bin");
fileInfo.appendChild(fileName);
return docToSave;
XML is almost never the easiest thing to do.

You can use to do that SAX or DOM, review this link: https://web.archive.org/web/1/http://articles.techrepublic%2ecom%2ecom/5100-10878_11-1044810.html
I think is that you want

SAXReader not re-ecape characters

I'm reading a XML file with dom4j. The file looks like this:
...
<Field>
hello, world...</Field>
...
I read the file with SAXReader into a Document. When I use getText() on a the node I obtain the followin String:
\r\n hello, world...
I do some processing and then write another file using asXml(). But the characters are not escaped as in the original file which results in error in the external system which uses the file.
How can I escape the special character and have
when writing the file?

You cannot easily. Those aren't 'escapes', they are 'character entities'. They are a fundamental part of XML. Xerces has some very complex support for 'unparsed entities', but I doubt that it applies to these, as opposed to the species that are defined in a DTD.

It depends on what you're getting and what you want (see my previous comment.)
The SAX reader is doing nothing wrong - your XML is giving you a literal newline character. If you control this XML, then instead of the newline characters, you will need to insert a \ (backslash) character following by the "r" or "n" characters (or both.)
If you do not control this XML, then you will need to do a literal conversion of the newline character to "\r\n" after you've gotten your string back. In C# it would be something like:
myString = myString.Replace("\r\n", "\\r\\n");

XML entities are abstracted away in DOM. Content is exposed with String without the need to bother about the encoding -- which in most of the case is what you want.
But SAX has some support for how entities are processed. You could try to create a XMLReader with a custom EntityResolver#resolveEntity, and pass it as parameter to the SAXReader. But I feat it may not work:
The Parser will call this method
before opening any external entity
except the top-level document entity
(including the external DTD subset,
external entities referenced within
the DTD, and external entities
referenced within the document
element)
Otherwise you could try to configure a LexicalHandler for SAX in a way to be notified when an entity is encountered. Javadoc for LexicalHandler#startEntity says:
Report the beginning of some internal
and external XML entities.
You will not be able to change the resolving, but that may still help.
EDIT
You must read and write XML with the SAXReader and XMLWriter provided by dom4j. See reading a XML file and writing an XML file. Don't use asXml() and dump the file yourself.
FileOutputStream fos = new FileOutputStream("simple.xml");
OutputFormat format = OutputFormat.createPrettyPrint();
XMLWriter writer = new XMLWriter(fos, format);
writer.write(doc);
writer.flush();

You can pre-process the input stream to replace & to e.g. [$AMPERSAND_CHARACTER$], then do the stuff with dom4j, and post-process the output stream making the back substitution.
Example (using streamflyer):
import com.github.rwitzel.streamflyer.util.ModifyingReaderFactory;
import com.github.rwitzel.streamflyer.util.ModifyingWriterFactory;
// Pre-process
Reader originalReader = new InputStreamReader(myInputStream, "utf-8");
Reader modifyingReader = new ModifyingReaderFactory().createRegexModifyingReader(originalReader, "&", "[\\$AMPERSAND_CHARACTER\\$]");
// Read and modify XML via dom4j
SAXReader xmlReader = new SAXReader();
Document xmlDocument = xmlReader.read(modifyingReader);
// ...
// Post-process
Writer originalWriter = new OutputStreamWriter(myOutputStream, "utf-8");
Writer modifyingWriter = new ModifyingWriterFactory().createRegexModifyingWriter(originalWriter, "\\[\\$AMPERSAND_CHARACTER\\$\\]", "&");
// Write to output stream
OutputFormat xmlOutputFormat = OutputFormat.createPrettyPrint();
XMLWriter xmlWriter = new XMLWriter(modifyingWriter, xmlOutputFormat);
xmlWriter.write(xmlDocument);
xmlWriter.close();
You can also use FilterInputStream/FilterOutputStream, PipedInputStream/PipedOutputStream, or ProxyInputStream/ProxyOutputStream for pre- and post-processing.