The actor Attribute

The actor attribute is optional, but if it is used, it must appear in a SOAPHeaderElement object. Its purpose is to indicate the recipient of a header element. The default actor is the message’s ultimate recipient; that is, if no actor attribute is supplied, the message goes directly to the ultimate recipient.

An actor is an application that can both receive SOAP messages and forward them to the next actor. The ability to specify one or more actors as intermediate recipients makes it possible to route a message to multiple recipients and to supply header information that applies specifically to each of the recipients.

For example, suppose that a message is an incoming purchase order. Its SOAPHeader object might have SOAPHeaderElement objects with actor attributes that route the message to applications that function as the order desk, the shipping desk, the confirmation desk, and the billing department. Each of these applications will take the appropriate action, remove the SOAPHeaderElement objects relevant to it, and send the message on to the next actor.

Although the SAAJ API provides the API for adding these attributes, it does not supply the API for processing them. For example, the actor attribute requires that there be an implementation such as a messaging provider service to route the message from one actor to the next.

An actor is identified by its URI. For example, the following line of code, in which orderHeader is a SOAPHeaderElement object, sets the actor to the given URI.

orderHeader.setActor("http://gizmos.com/orders");

Additional actors can be set in their own SOAPHeaderElement objects. The following code fragment first uses the SOAPMessage object message to get its SOAPHeader object header. Then header creates four SOAPHeaderElement objects, each of which sets its actor attribute.

SOAPHeader header = message.getSOAPHeader();
SOAPFactory soapFactory = SOAPFactory.newInstance();

String nameSpace = "ns";
String nameSpaceURI = "http://gizmos.com/NSURI";

QName order = new QName(nameSpaceURI, "orderDesk", nameSpace);
SOAPHeaderElement orderHeader = header.addHeaderElement(order);
orderHeader.setActor("http://gizmos.com/orders");

QName shipping = new QName(nameSpaceURI, "shippingDesk", nameSpace);
SOAPHeaderElement shippingHeader = header.addHeaderElement(shipping);
shippingHeader.setActor("http://gizmos.com/shipping");

QName confirmation = new QName(nameSpaceURI, "confirmationDesk", nameSpace);
SOAPHeaderElement confirmationHeader = header.addHeaderElement(confirmation);
confirmationHeader.setActor("http://gizmos.com/confirmations");

QName billing = new QName(nameSpaceURI, "billingDesk", nameSpace);
SOAPHeaderElement billingHeader = header.addHeaderElement(billing);
billingHeader.setActor("http://gizmos.com/billing");

The SOAPHeader interface provides two methods that return a java.util.Iterator object over all the SOAPHeaderElement objects that have an actor that matches the specified actor. The first method, examineHeaderElements, returns an iterator over all the elements that have the specified actor.

java.util.Iterator headerElements =
    header.examineHeaderElements("http://gizmos.com/orders");

The second method, extractHeaderElements, not only returns an iterator over all the SOAPHeaderElement objects that have the specified actor attribute but also detaches them from the SOAPHeader object. So, for example, after the order desk application did its work, it would call extractHeaderElements to remove all the SOAPHeaderElement objects that applied to it.

java.util.Iterator headerElements =
    header.extractHeaderElements("http://gizmos.com/orders");

Each SOAPHeaderElement object can have only one actor attribute, but the same actor can be an attribute for multiple SOAPHeaderElement objects.

Two additional SOAPHeader methods, examineAllHeaderElements and extractAllHeaderElements, allow you to examine or extract all the header elements, whether or not they have an actor attribute. For example, you could use the following code to display the values of all the header elements:

Iterator allHeaders = header.examineAllHeaderElements();
while (allHeaders.hasNext()) {
    SOAPHeaderElement headerElement = (SOAPHeaderElement)allHeaders.next();
    QName headerName = headerElement.getElementQName();
    System.out.println("\nHeader name is " + headerName.toString());
    System.out.println("Actor is " + headerElement.getActor());
}