After I got XML data, how to parse it and transfer to JSON?

In Jers开发者_高级运维ey RESTful frame work, I know I can get xml data in client as following:

private static final String BaseURI = "http://DOMAN.com";

ClientConfig config = new DefaultClientConfig();

Client client = Client.create(config);

WebResource service = client.resource(BaseURI);

String xmlData = service.path("rest").path("todos").accept(
                MediaType.APPLICATION_XML).get(String.class)

My question is how can I parse the xmlData then? I would like to get the needed data from xmlData, and transfer the needed data to JSON, what is the best way to implement this?

As a general rule, NEVER convert straight from XML to JSON (or vice versa) if you do not have to. Rather, bind data from XML or JSON to POJOs, then do the other conversion. While it may seem non-intuitive this results in cleaner result and less problems, since conversions between POJOs and data formats have much more options, mature, well-designed libs; and POJOs are easier to configure (with annotations) and have more metadata to guide conversion process. Direct conversions libs (like Jettison, see below) are plagued with various issues; often producing "franken-JSON", JSON that is technically correct but looks alien because of added constructs needed by conversion.

In case of Jersey, then, use JAXB for XML to/from POJOs, and Jackson for doing the same with JSON. These are libraries Jersey uses anyway; and direct usage is quite easy.

If you absolutely insist on direct conversion, you could try Jettison, but be prepared to hit a problem with Lists, arrays and Maps, if you need them (esp. single-element arrays -- arrays are problematic with XML, and auto-conversion often goes wrong).

If your service doesn't provide JSON as an option already (what happens if you change MediaType.APPLICATION_XML to MediaType.APPLICATION_JSON?), then I believe you have a few options, which I list in order of my preference.

Option 1: You have an XML schema for the the data If you have an XML schema for the returned XML, you could use xjc to generate the JAXB annotated java classes and then leverage jackson to convert the instances to JSON data. I think this will get you going fast by leveraging this libraries over doing the parsing youself. Jackson is a robust library, used by glassfish for their Jersey(JAX-RS) implementation and I don't feel there is any risk in depending on this library.

Option 2: Use the json.org library, but I've had significant problem with this library having to do with its reflection-based methodology, etc. That said, it might work well for you...and you can test relatively easily and see if it does meet your requirements. If so...you're done! =)

Option 3: You don't have the XML schema and/or you want more control as @Falcon pointed out, you can always use traditional XML parsing technologies to parse the XML into whatever you want. I'm partial to SAX parsing, but DOM could work depending on xml side

Regards,

Steve

Simplest and easiest way would be using org.json package : http://json.org/javadoc/org/json/XML.html

XML.toJSONObject(xmlData).toString()

Just this one line apart from necessary import statement will do it all.

Now that i have mentioned org.json library, lot of people may comment bad about it. Remember, I have said the simplest and easiest way, not the best or the most performant way ;-)

In case you are using maven, add this dependency :

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20090211</version>
</dependency>

Do you have any access to the "lower level interface" that generates the XML? If you do, the only change needed is to have the xml objects annotated with "@XmlRootElement". Then, you can just pass back the XMLobject as JSON without any further code.

Check Jsonix. If you have an XML schema, you can generate XML-JSON mappings and unmarshal/marshal XML in JavaScript. Very similar to JAXB (which Steve Siebert mentioned), but works on client.

// The PO variable provides Jsonix mappings for the purchase order test case
// Its definition will be shown in the next section

var PO = { };

// ... Declaration of Jsonix mappings for the purchase order schema ...

// First we construct a Jsonix context - a factory for unmarshaller (parser)
// and marshaller (serializer)
var context = new Jsonix.Context([ PO ]);

// Then we create an unmarshaller
var unmarshaller = context.createUnmarshaller();

// Unmarshal an object from the XML retrieved from the URL
unmarshaller.unmarshalURL('/org/hisrc/jsonix/samples/po/test/po-0.xml',
    // This callback function will be provided with the result
    // of the unmarshalling
    function(result) {
        // We just check that we get the values we expect
        assertEquals('Alice Smith', result.value.shipTo.name);
        assertEquals('Baby Monitor', result.value.item[1].productName);
    });