convert javaobjects to xml and xml to java objects dynamically

[kiran manohar]

hi,
i have a class called Converter which needs to do 4 things.
1) It will receive a xml file .this xml file i need to convert to a object with the datas in the xml stored in the object.
for ex.
if i get a xml file like say
foo.xml[this xml file will change]
<mail>
<to>[e-mail]</to>
<from>[e-mail]</from>
<subject>Hello Raj</subject>
<message>Have a nice time</message>
</mail>
now this xml files data between the markups must be initialized in a java object. and that object which is initialized must be returned by my class.
2) i will receive a object which has been initialized with data . now i need to read the data in the object and write them to a xml file.
3) i will receive a xml string representing some content in it to my class , this xml string needs to be read and its data need to be written to an object.[note: we can assume the content to be the data between the tags in the above xml file]
4) i will receive an object , to which my class Converter must read its content and return a xml string with the objects content.this xml string i need to return from my class.
My question is what xml parser should i use , jaxb or castor have given examples which are static in the sense that they advocate getter and setter methods which are based on the xml file. but the xml file i get could contain any structure, so i need a parser which would fix my problem dynamically. in future i need to parse a xml schema file also .so pl take that into consideration and recommend a xml parser which will convert xml file / schema to java objects and vice versa.this looks tough for me as i am new to databinding and xml.Any recommendations will be helpful.
Thanks in advance.
Kiranmanohar

[Lasse Koskela]

How about just reading the XML into a DOM tree and implementing the conversion manually? I haven't had much experience with binding products such as JAXB or Castor so I cannot say whether they would be helpful in this kind of generic binding.

[kiran manohar]

i am new to xml& java databinding , u had mentioned about reading the xml in a dom tree
could u give me few examples to get me started.
Thanks in advance
Kiranmanohar

[Lasse Koskela]

Here's a good example of how to use the DocumentBuilder utility for parsing an XML file into an org.w3c.dom.Document object.

[kiran manohar]

after parsing the xml file how to use the Document object to initialize my object.thanks for ur help Lasse.

[Lasse Koskela]

You traverse through the DOM tree, pick element values where appropriate, and call setThisAndThat("...") on your domain object.
Here's a very simple example:

    private ArrayList convertDocumentIntoDomainObjects(Document doc) {
        ArrayList domainObjects = new ArrayList();
        Element root = doc.getDocumentElement();
        NodeList agentElements = root.getChildNodes();
        for (int i=0; i < agentElements.getLength(); i++) {
            Node agentElement = agentElements.item(i);
            if (agentElement.getNodeType() != Node.ELEMENT_NODE) {
                // ignoring element due to wrong node type
                continue;
            }
            
            String name = agentElement.getNodeName();
            if (name != null && name.equals("agent")) {
                domainObjects.add(convertAgentElementIntoObject((Element)agentElement));
            }
        }
        
        return domainObjects;
    }
    /**
     * Converts a given <agent> element into an Agent object.
     */
    private Agent convertAgentElementIntoObject(Element agentElement) {
        Agent agent = new Agent();
        agent.setName(agentElement.getAttribute("name"));
        agent.setIataNumber(agentElement.getAttribute("iatanumber"));
        return agent;
    }

[kiran manohar]

Thanks Lasse,
Ur coding is working. But the coding is not generic i presume. that is if i want to send any xml file and parse it to java objects how to go about it
Regards
Kiranmanohar

[kiran manohar]

lasse,
i have a doubt . u said that DOM is to be used in the coding. my doubt is would it parse an xml schema as well as a xml file and also a xml string.
that is a string object holding xml tags in it.
Thanks
Regards
Kiranmanohar

[Lasse Koskela]

that is if i want to send any xml file and parse it to java objects how to go about it

Either you need to implement your own Java-to-XML mapping or use an existing XML data binding API such as Sun's JAXB or Castor.

u said that DOM is to be used in the coding. my doubt is would it parse an xml schema as well as a xml file and also a xml string.
that is a string object holding xml tags in it.

Could you rephrase this 'cause I didn't quite get what you're asking?

[Lasse Koskela]

By the way, the DOM tree generated by a DOM parser is as generic a Java object representation of your arbitrary XML document as possible...

[Pradeep bhatt]

JAXB generates objects for a specific schema , so they are not generic.

[Phil Chuang]

There's an open source package called skaringa that does objects -> xml -> objects that does what you want.
http://skaringa.sourceforge.net/
I built myself a handy little wrapper around it and I use it like

ObjectXMLConverter.objectToXml (someObject, "someObject.xml");
SomeObject loadedObject = (SomeObject) ObjectXMLConverter.xmlToObject ("someObject.xml");
ObjectXMLConverter.classToXsd (someObject.getClass(), "SomeObject.xsd");

[Lasse Koskela]

http://skaringa.sourceforge.net/

Thanks! I had somehow forgotten Skaringa completely.

[kiran manohar]

thanks lasse
for the skaringa links, but for now i will continue with DOM.in the coding for dom u have used Agent . in which package does this Agent Class or Interface is used and how to add it. i m using jdk1.4 by the way.
Regards
Kiranmanohar