How can a Spring Soap interceptor modify the contents of a message?

Question

I'm trying to write an interceptor for a web service that will modify the contents of the Soap message before is sent on to the endpoint. If a client sent a message where the value of some element is 1, I want to be able to alter that element to a 2 so that, when the message arrives at the endpoint, it looks as if the client submitted a 2 instead of a 1. I'm not sure if this is a difficult task which is elluding me, or an easy task which I am making harder than it needs to be.

I have stepped through some of the Spring interceptors; but the validation and logging interceptors don't every alter the message that is in transit. The Wss4jSecurityInterceptor does add some properties to the MessageContext; but I haven't been able to leverage anything that it is doing. I have a shell of an interceptor; but nothing that is doing anything of any value.

public boolean handleRequest(MessageContext messageContext, Object endpoint)
        throws Exception {

    SaajSoapMessage saajSoapMessage = (SaajSoapMessage) messageContext
            .getRequest();
    SOAPMessage soapMessage = saajSoapMessage.getSaajMessage();
    SOAPBody soapBody = soapMessage.getSOAPBody();

    return true;
}

I was hoping there was a chance that soembody else had already solved this particular problem. Any insight would be appreciated. Thanks.

Answer 1

Modifying the payload is a little bit tricky. The only way I've found to make this work is to use the getPayloadSource() and getPayloadResult() methods on SoapBody, which expose javax.xml.transform-friendly objects for manipulating the data.

It's annoyingly heavyweight, but you can do something like this:

Transformer identityTransform = TransformerFactory.newInstance().newTransformer();
DOMResult domResult = new DOMResult();
identityTransform.transform(soapBody.getPayloadSource(), domResult);

Node bodyContent = domResult.getNode(); // modify this

identityTransform.transform(new DOMSource(bodyContent), soapBody.getPayloadResult());

I'd love to see a better way of doing this.

Answer 2

I realized that it was easer to alter the request at a later point. I did not need to modify the original SOAP message, so long as I was able to modify the data before it reached my endpoint.

The endpoints I am working with all extend AbstractDom4jPayloadEndpoint - so I wrapped these endpoints in a proxy that allowed me to modify the request element before proceeding to my endpoint. i.e.:

public class MyProxyEndpoint extends AbstractDom4jPayloadEndpoint

    @Override
    protected Element invokeInternal( 
        Element requestElement,
        Document responseDocument ) throws Exception
    {
        if( requestElement != null )
        {
            // alter request element
        }

        return ( Element ) this.invokeMethod.invoke( 
            this.target,
            requestElement,
            responseDocument );
    }

Answer 3

I modified the code in this answer to insert an <authentication/> element into all SOAP body requests:

@Override
public boolean handleRequest(MessageContext messageContext) throws WebServiceClientException {
    logger.trace("Enter handleMessage");
    try {
        SaajSoapMessage request = (SaajSoapMessage) messageContext.getRequest();
        addAuthn(request);
    } catch (Exception e) {
        logger.error(e.getMessage(),e);
    }

    return true;
}

protected void addAuthn(SaajSoapMessage request) throws TransformerException {
    Transformer identityTransform = TransformerFactory.newInstance().newTransformer();
    DOMResult domResult = new DOMResult();
    identityTransform.transform(request.getPayloadSource(), domResult);

    Node bodyContent = domResult.getNode();
    Document doc = (Document) bodyContent;
    doc.getFirstChild().appendChild(authNode(doc));

    identityTransform.transform(new DOMSource(bodyContent), request.getPayloadResult());
}

protected Node authNode(Document doc) {
    Element authentication = doc.createElementNS(ns, "authentication");
    Element username = doc.createElementNS(ns, "username");
    username.setTextContent(authn.getUsername());
    Element password = doc.createElementNS(ns, "password");
    password.setTextContent(authn.getPassword());
    authentication.appendChild(username);
    authentication.appendChild(password);
    return authentication;
}

This solution was used because the WebServiceMessageCallback would require me to change the Document, and the SaajSoapMessageFactory is activated before the soap body has been inserted by the configured Jaxb2Marshaller.