Java : JAX-WS Dispatch

This page last changed on Oct 05, 2006 by Kees de Kooter

Web service client applications may choose to work at the XML message level by using the Dispatch<T> APIs. The<T> interface provides support for the dynamic invocation of service endpoint operations.

Four Message Exchange Protocols(MEP) are supported: request-response, one way, asynchronous polling, and callback. Each of these invocation MEPs are required with JAXB data bound java.lang.Object, javax.xml.transform.Source, javax.xml.soap.SOAPMessage and javax.activation.DataSource object requests.

The acts as a factory for the creation of Dispatch<T> instances. In addition, a Dispatch<T> instance is created in either Service.Mode.PAYLOAD or Service.Mode.MESSAGE modes. A javax.xml.soap.SOAPMessage request can only be used with a Dispatch<T> instance of Service.Mode.MESSAGE and using the SOAP Binding. A javax.activation.DataSource request can only be used with a Dispatch<T> instance of Service.Mode.MESSAGE and using the XML/HTTP Binding.

Note that the Dispatch<T>instance simply acts as a conduit for the request. No validation of the message is required to be performed by the implementation, though some may catch errors during request processing. It is up to the client program to supply well-formed XML requests.

Programming Model

Create a dynamic Service.

The acts as a factory for the creation of a dynamic Service. When created for use with Dispatch<T> APIs the Service created can be either a Service that has knowledge of the binding information of a known Service or no knowledge of any specific Service.

That is, when the Service is created with a WSDL file the port(s) binding ID, QName, and endpoint address are known to the Service.

The methods to create a dynamic Service are shown here:

Service service = Service.createService(QName serviceQName);
Service service = Service.createService(URL wsdlLocation, QName serviceQName);

A Dispatch<T> instance must be bound to a specific port and endpoint before use. The service has an addPort(QName portName, URI bindingID, String endpointAddress) method that the client program can invoke for Dispatch<T> objects. Ports created using this method can only be used with Dispatch<T> instances.

If the Service has been created with WSDL binding information the the port need not be added as the Dispatch<T> instance will be created specific for the binding information provided in the supplied WSDL file.

Developers who have used web service applications in the past are familiar with the port QName and endpoint address parameters of this method. The JAX-WS 2.0.1 M1implementation supports three BindingURI's, that of the SOAP 1.1, the SOAP 1.2 and XML/HTTP Binding. For more information on SOAP 1.2 support please refer to the SOAP 1.2 documents. For the XML/HTTP binding please see chapter 11 of the JAX-WS 2.0 PFD Specification.

The addition of the SOAP 1.1 port using the Service API is shown here:

service.addPort(QName portName, String SOAPBinding.SOAP11HTTP_BINDING, String endpointAddress);

SOAP 1.2 support has been implemented for Dispatch. This requires only one change in the programming model. The addition of the SOAP 1.2 port using the Service API is shown here:

service.addPort(QName portName, String SOAPBinding.SOAP12HTTP_BINDING, String endpointAddress);

XML/HTTP binding support has been implemented for Dispatch. The creation of the XML/HTTP port using the Service API is shown here:

service.addPort(QName portName, String HTTPBinding.HTTP_BINDING, String endpointAddress);

Create a Dispatch<T> instance.

The Dispatch<T> object can be created using either of these two Service methods:

Dispatch dispatch = service.createDispatch(QName portName, Class clazz, Service.Mode mode);
Dispatch dispatch = service.createDispatch(QName portName, JAXBContext jaxbcontext, Service.Mode mode);

For a javax.xml.transform.Source and JAXB data binding java.lang.Object Dispatch<T> can be created in both Service.Mode.PAYLOAD and Service.Mode.MESSAGE modes. A javax.xml.soap.SOAPMessage can only be created in Service.Mode.MESSAGE mode. The first form of the createDispatch method is used to create a javax.xml.transform.Source or javax.xml.soap.SOAPMessage specific to the Dispatch<T> instance.

A JAXB object-specific instance can only be created using the second method listed above.

It is important to note that once the Dispatch<T> instance is created it is static. That is, its Service.Mode or request type can not be changed. The instance can be reused given the caveat that if it is a JAXB-specific Dispatch<T> it must be reused with objects known to the same JAXBContext.

Set the context Map<String, Object> for the request.

The Dispatch<T> interface extends the interface. The BindingProvider interface defines accessor methods for the request and response context maps. Standard BindingProviderproperties are defined by the JAX-WS 2.0 specification and the client program may set and get these properties. The application may also define application-specific properties, but the specification discourages this for portability reasons.

Prepare the message request.

This is the client developer's responsibility. For examples of how to prepare specific request types refer to the Dispatch<T> sample applications.

Invoke the web service request.

Four types of invocation MEPs are supported using the methods below. In methods that produce a response, the type of Object returned will be of the same type as the request. For example, a SOAPMessage request will return a SOAPMessage response.

Object response = dispatch.invoke(T);
Response<T> response = dispatch.invokeAsync(T);
Future<?> response = dispatch.invokeAsync(T, AsyncHandler);

Dispatch and Asynchronous Invocations

Asynchronous invocations require special consideration. The first form of the invokeAsync method is a polling method. The response, Response<T>,returns to the user immediately and may be polled for completion. In the meantime, the client program can do other work.

The<T> implements the java.util.concurrent.Future<T> interface that is included in J2SE 5.0. The Response<T> object returns the actual response via its get method, which blocks if the response is not ready to be returned.

The Future<T> interface also has a cancel method that will attempt to cancel the request invocation if the request is being invoked.

Faults returned from the service or exceptions thrown during the invocation are returned when the Response<T> get method is called. Because the execution doesn't occur in the main thread, the exception or fault returned is wrapped in an java.util.concurrent.ExecutionException. To obtain the actual cause use the getCause method of ExecutionException.

For more information on the java.util.concurrent.Future<?> interface see the J2SE 5.0 documentation.

public interface Response<T>extends java.util.concurrent.Future<T>{
       Map<String, Object> getContext();

The second form of the invokeAsync method has a second parameter of type The purpose of the AsyncHandler is to get and handle the the response or any fault thrown in an application-specific way. The AsyncHandler has a method handleResponse(Response<T>) that takes a<T>parameter. This method gets the response or any faults and processes them according to behavior defined in the application. Note that it is the responsibility of the client program to implement the asynchronous handler.

class ResponseHandler implements{
        public handleResponse(Response<T>);

This form of the asynchronous invocation method returns a Future<?> object with wildcard type. As in the asynchronous poll invocation, the Future<T> object can be polled to see if the response is ready. However, calling the get method will not return the response of the invocation, but an object of indeterminate type.

Examples of synchronous and asynchronous invocations are shown in the Dispatch<T> samples. For convenience an example of Response<T> usage is display here:

Response<Source> response = dispatch.invokeAsync(Source);
while (!response.isDone()){
//go off and do some work

try {
        //get the actual result
        Source result = (javax.xml.transform.Source)response.get();
        //do something with the result
} catch (ExecutionException ex){
        //get the actual cause
        Throwable cause = ex.getCause();
} catch (InterupptedException ie){
        //note interruptions
        System.out.println("Operation invocation interrupted");