Developing Diameter Applications

Using the Diameter Sh Interface Application

The following sections describe how to use the Diameter Sh interface application, based on the Oracle Communications Converged Application Server Diameter protocol implementation, in your own applications:

Overview of Profile Service API and Sh Interface Support

The IMS specification defines the Sh interface as the method of communication between the Application Server (AS) function and the Home Subscriber Server (HSS), or between multiple IMS Application Servers. The AS uses the Sh interface in two basic ways:

The user data available to an AS may be defined by a service running on the AS (repository data), or it may be a subset of the user’s IMS profile data hosted on the HSS. The Sh interface specification, 3GPP TS 29.328, defines the IMS profile data that can be queried and updated via Sh. All user data accessible via the Sh interface is presented as an XML document with the schema defined in 3GPP TS 29.328.

The IMS Sh interface is implemented as a provider to the base Diameter protocol support in Oracle Communications Converged Application Server. The provider transparently generates and responds to the Diameter command codes defined in the Sh application specification. A higher-level Profile Service API enables SIP Servlets to manage user profile data as an XML document using XML Document Object Model (DOM). Subscriptions and notifications for changed profile data are managed by implementing a profile listener interface in a SIP Servlet.

Oracle Communications Converged Application Server includes a provider for the Diameter Sh interface. Providers to support additional interfaces defined in the IMS specification may be provided in future releases. Applications using the profile service API will be able to use additional providers as they are made available.

Enabling the Sh Interface Provider

See Configuring Diameter Sh Client Nodes and Relay Agents in Configuring Network Resources for full instructions on setting up Diameter support.

Overview of the Profile Service API

Oracle Communications Converged Application Server provides a simple profile service API that SIP Servlets can use to query or modify subscriber profile data, or to manage subscriptions for receiving notifications about changed profile data. Using the API, a SIP Servlet explicitly requests user profile documents via the Sh provider application. The provider returns an XML document, and the Servlet can then use standard DOM techniques to read or modify profile data in the local document. Updates to the local document are applied to the HSS after a “put” operation.

Creating a Document Key for Application-Managed Profile Data

Servlets that manage profile data can explicitly obtain an Sh XML document from a factory using a key, and then work with the document using DOM.

The document selector key identifies the XML document to be retrieved by a Diameter interface, and uses the format protocol://uri/reference_type[/access_key].

The protocol portion of the selector identifies the Diameter interface provider to use for retrieving the document. Sh XML documents require the sh:// protocol designation.

With Sh document selectors, the next element, uri, generally corresponds to the User-Identity or Public-Identity of the user whose profile data is being retrieved. If you are requesting an Sh data reference of type LocationInformation or UserState, the URI value can be the User-Identity or MSISDN for the user.

Table 2-1 summarizes the possible URI values that can be supplied depending on the Sh data reference you are requesting. 3GPP TS 29.328 describes the possible data references and associated reference types in more detail.

The final element of the document selector, reference_type, specifies the data reference type being requested. For some data reference requests, only the uri and reference_type are required. Other Sh requests use an access key, which requires a third element in the document selector corresponding to the value of the Attribute-Value Pair (AVP) defined in the key.

Table 2-2 summarizes the required document selector elements for each type of Sh data reference request.

Using a Constructed Document Key to Manage Profile Data

Oracle Communications Converged Application Server provides a helper class, com.bea.wcp.profile.ProfileService, to help you easily retrieve a profile data document. The getDocument() method takes a constructed document key, and returns a read-only org.w3c.dom.Document object. To modify the document, you make and edit a copy, then send the modified document and key as arguments to the putDocument() method.

Oracle Communications Converged Application Server caches the documents returned from the profile service for the duration of the service method invocation (for example, when a doRequest() method is invoked). If the service method requests the same profile document multiple times, the subsequent requests are served from the cache rather than by re-querying the HSS.

Listing 2-1 shows a sample SIP Servlet that obtains and modifies profile data.

package demo;

import com.bea.wcp.profile.*;

import javax.servlet.sip.SipServletRequest;

import javax.servlet.sip.SipServlet;

import org.w3c.dom.Document;

import java.io.IOException;

public class MyServlet extends SipServlet {

      private ProfileService psvc;

      public void init() {

        psvc = (ProfileService) getServletContext().getAttribute(ProfileService.PROFILE_SERVICE);

      }

      protected void doInvite(SipServletRequest req) throws IOException {

        String docSel = "sh://" + req.getTo() + "/IMSUserState/";

        // Obtain and change a profile document.

        Document doc = psvc.getDocument(docSel); // Document is read only.

        Document docCopy = (Document) doc.cloneNode(true);

        // Modify the copy using DOM.

        psvc.putDocument(docSel, docCopy); // Apply the changes.

      }

}

Monitoring Profile Data with ProfileListener

The IMS Sh interface enables applications to receive automatic notifications when a subscriber’s profile data changes. Oracle Communications Converged Application Server provides an easy-to-use API for managing profile data subscriptions. A SIP Servlet registers to receive notifications by implementing the com.bea.wcp.profile.ProfileListener interface, which consists of a single update method that is automatically invoked when a change occurs to profile to which the Servlet is subscribed. Notifications are not sent if that same Servlet modifies the profile information (for example, if a user modifies their own profile data).

Prerequisites for Listener Implementations

In order to receive a call back for subscribed profile data, a SIP Servlet must do the following:

Implementing ProfileListener describes how to implement ProfileListener and use the susbscribe method. In addition to having a valid listener implementation, the Servlet must declare itself as a listener in the sip.xml deployment descriptor file. For example, it must add a listener element declaration similar to:

<listener>

   <lisener-class>com.mycompany.MyLisenerServlet</listener-class>

</listener>

Implementing ProfileListener

Actual subscriptions are managed using the subscribe method of the com.bea.wcp.profile.ProfileService helper class. The subscribe method requires that you supply the current SipApplicationSession and the key for the profile data document you want to monitor. See Creating a Document Key for Application-Managed Profile Data.

Applications can cancel subscriptions by calling ProfileSubscription.cancel(). Also, pending subscriptions for an application are automatically cancelled if the application session is terminated.

Listing 2-2 shows sample code for a Servlet that implements the ProfileListener interface.

package demo;

    import com.bea.wcp.profile.*;

    import javax.servlet.sip.SipServletRequest;

    import javax.servlet.sip.SipServlet;

    import org.w3c.dom.Document;

    import java.io.IOException;

    public class MyServlet extends SipServlet implements ProfileListener {

      private ProfileService psvc;

      public void init() {

        psvc = (ProfileService) getServletContext().getAttribute(ProfileService.PROFILE_SERVICE);

      }

      protected void doInvite(SipServletRequest req) throws IOException {

        String docSel = "sh://" + req.getTo() + "/IMSUserState/";

        // Subscribe to profile data.

        psvc.subscribe(req.getApplicationSession(), docSel, null);

}

      public void update(ProfileSubscription ps, Document document) {

        System.out.println("IMSUserState updated: " + ps.getDocumentSelector());

      }

    }