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Web service client applications may choose to work at the XML message level by using the
Dispatch<T> APIs. The
javax.xml.ws.Dispatch<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
javax.xml.ws.Service 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.
Service.
The
javax.xml.ws.Service 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.create(QName serviceQName); Service service = Service.create(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. JAX-WS RI 2.2.6 supports three
Binding URI'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);
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.
Map<String, Object> for the request.
The
Dispatch<T> interface extends the
javax.xml.ws.BindingProvider interface. The
BindingProvider interface defines accessor methods for the request and response context maps. Standard
BindingProvider properties 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.
This is the client developer's responsibility. For examples of how to prepare specific request types refer to the
Dispatch<T> sample applications.
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); dispatch.invokeOneway(T); Response<T> response = dispatch.invokeAsync(T); Future<?> response = dispatch.invokeAsync(T, AsyncHandler);
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
javax.xml.ws.Response<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
javax.xml.ws.AsyncHandler. 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
javax.xml.ws.Response<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 javax.xml.ws.AsyncHandler{
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");
}