Streaming custom objects - soap

Question

I am building a SOAP webservice. I am using JAX-WS to create this service and deploying it on a Glassfish 3.1.2 server.
I have no problem having this service return a String build with the XML representation of what I want. I can also get it to return a specific object. What I am having issues with is streaming this resource.
This is what I have so far :
Interface :
#MTOM
#WebService
#XmlRootElement(name="root.element.class.location")
#SOAPBinding(style = Style.RPC, use=Use.LITERAL)
public interface ResultsServer {
#WebMethod
#XmlMimeType("text/xml")
public Test getResultDataAsXML(#WebParam(name="Id") Integer id) throws Exception;
}
Implementation :
---- Edit ----
This is where I would like to stream my resource. Let's say I need my results object becomes extremely large, I don't want to hold this is memory and would like to start sending it without holding it. (commented this in code)
#WebService(endpointInterface = "my.endpoint.class")
#StreamingAttachment(parseEagerly=true, memoryThreshold=4000000L)
public class ResultsServerImpl implements ResultsServer {
#Override
public Test getResultDataAsXML(Integer id) throws Exception {
Test results = new Test();
for(int i=0; i<[very large number]; i++) {
results.getResults().add("here : " + i);
/**at one point, this is too large to hold in memory
I would like to be able to start returning the object here
so it is not taking up all available memory */
}
return results; //or close the stream
}
}
---- End Edit ----
And my Test class is a simple class looking like this :
public class Test {
private ArrayList<String> results;
public Test() {
results = new ArrayList<String>();
}
public ArrayList<String> getResults() {
return results;
}
public void setResults(ArrayList<String> results) {
this.results = results;
}
}
Let's assume that this Test object becomes very big (and more complexe). I need to be able to stream this object. How would I go to proceed in streaming this.
Ideally, I would like to keep the structure of this object.
From what I have read so far, I would need to convert this object in some sort of DataHandler and return this object.
Any help is welcome! Thank you.

Answer 1

The JAX-WS implementation will leverage a JAXB implementation to marshal the object (most likely to a StAX XMLStreamWriter) so the output will be streamed (there won't be an XML document created in memory).
#BlaiseDoughan I think you've worded this the way I was looking for.
Yes that would be to prevent the instance of Test of fully being saved
in memory. Is there a way to do this?
If you want the data to appear in the messages as XML (as opposed to a SOAP attachment), the you could leverage JAXB's marshal events. In the beforeMarshal event you could load data into an object and then clear it in the afterUnmarshal method. Ultimately all the data will be pulled in, but it won't all be referenced at the same time.
http://docs.oracle.com/javase/6/docs/api/javax/xml/bind/Unmarshaller.html#unmarshalEventCallback

Answer 2

I would recommend using the xstream (http://x-stream.github.io/) library from thoughtworks for your streaming as it is bindable on both sides of your service and is compatible with SOAP envelops. In fact there is even an integration with ActiveSOAP.
An example of a SOAP envelope wrapped xstream object can be seen at http://jira.codehaus.org/secure/attachment/19097/SoapEnvelopeTestCase.java. A full usage from jboss can be seen at https://issues.jboss.org/secure/attachment/12325534/SOAPClient.java?_sscc=t.
XStream has been used for some very large streaming processes (I've used it for some large 100+ MB text objects without issue).