在JAVA中如何跳到XML中的特定节点？

Question

I have xml having data something like this

<A Name="">
</A>
<A Name="">
</A>
.....

How can i jump to some particular node and read it - like 3rd tag- A by using SAX parser

Answer 1

If you want to jump to a sub-node you must use the DOM API and not SAX.

  // load the document
  DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  DocumentBuilder db = dbf.newDocumentBuilder(); 
  Document doc = db.parse(new File(filename));

  // prepare result list
  ArrayList<Element> res = new ArrayList<Element>();

  // prepare to use xpath
  XPath xpath = XPathFactory.newInstance().newXPath();
  // read 3rd A element
  NodeList list = (NodeList) xpath.compile("/A[3]")
      .evaluate(doc, XPathConstants.NODESET);

  // copy the DOM element in the result list
  for (int i = 0; i < list.getLength(); i++) {
    res.add((Element) list.item(i));
  }

Please note that contrary to SAX it will read the whole document before allowing you to access it.

Answer 2

You cannot jump to (skip all elements before) a certain element using SAX. It reads sequentially all elements and returns them to your ContentHandler . All you can do, is skip the parsing, after you found the relevant element by throwing an exception from within the ContentHandler.

If you're looking for a kind of random access to the XML elements, then you should definitively consider DOM as pointed out by @Guillaume.

Answer 3

You can "jump" to a particular XML tag, but reading the tags in sequence. There is no reliable way to skip tags without reading.

Answer 4

Your best off using the Java StAX API. The Oracle Java Tutorial Site has a great read on how to work with it. It's very clean and simple for doing basic read/parse from XML.