1 Using the Diameter Base Protocol API

Creating a Diameter Bean Using Annotations

Example 1-1 shows an implementation of a Diameter Bean, ExamplePOJO, that listens to RoApplication messages.

@DiameterBean(applicationId = "4")
public class ExamplePOJO {
 
  @Inject DiameterSessionSource source;
 
  public void handleCCR(@Observes CCR ccr) {
    RoSession session = (RoSession) ccr.getSession();
    SipApplicationSession sas = source.getApplicationSession(session);
    //... Business logic...
  }
 
  public void handleSTR(@Observes @DiameterObserver(code=275) Message msg) {
    RoSession session = (RoSession) msg.getSession();
    SipApplicationSession sas = source.getApplicationSession(session);
    //... Business logic...
  }
}

The annotation, @DiameterBean, marks the Java class as a Diameter Bean. The Diameter stack looks for Common Dependency Injection (CDI) observer methods for feeding the requests or responses to the Diameter Bean. The method arguments and the command code, if any, act as a filter for feeding the messages.

Such an architecture avoids the need for registering a listener for subsequent messages in the Diameter session, since the Diameter session information can be obtained from the message.

The RoApplication can then be injected into a SIP servlet as shown in Example 1-2.

public class FooServlet {
 
  @Inject @DiameterContext(applicationId = "4")
  Application roApp;
 
  @Inject
  DiameterSessionSource source;
 
  void doInvite(SipServletRequest request) throws IOException {
    RoSession session = (RoSession) source.createSession(roApp, request.getApplicationSession());
    CCR ccr = session.createCCR(RequestType.INITIAL);
    ccr.send();
  }
}

Built-in CDI Beans

The Diameter stack adds built-in CDI beans which can be injected into SIP Servlets and Diameter Beans.

public class ExampleServlet extends SipServlet {
  @Inject @DiameterContext(applicationId = 4)
  private Application application;
  ...
}

public class ExampleServlet extends SipServlet {
  @Inject
  private RoApplication roApplication;
  @Inject
  private RfApplication rfApplication;
  @Inject
  private ShApplication shApplication;
  ...
}

Diameter Bean Selection

The Diameter stack selects the bean to handle incoming requests based on the following different criteria:

• Application Identifier

• Peer (host/realm)

• Origin (origin host/ origin realm)

• Destination (destination host / destination realm)

The stack finds the most specific Diameter bean to handle the message, irrespective of the application in which it is packaged. The following rules determine the most specific bean:

• If the bean contains and matches all the selection criteria annotations, then it is considered most specific.

• If the bean contains and matches a fewer number of selection critera annotations, then priority is given in the following order:

  Application then Peer then Destination then Origin.

• For matching a node (Peer, Origin or Destination), priority is given to host rather than realm.

Example 1-5 shows a bean with a more complicated set of selection criteria. When a Diameter message comes in, ExampleBean1 is selected first, followed by the remaining beans in the following order:

ExampleBean2 then ExampleBean3 then ExampleBean4 then ExampleBean5

@DiameterBean(
applicationId = 4,
peers = { @DiameterNode(host = "ro.server", realm = "weblogic.com") },
origins = { @DiameterNode(host = "originserver", realm = "originserver.com"),
@DiameterNode(host = "ro.client", realm = "weblogic.com") },
destinations = { @DiameterNode(host = "ro.server", realm = "weblogic.com") })
public class ExampleBean1 {
}
 
//specify peers.
@DiameterBean(
applicationId = 4,
peers = { @DiameterNode(host = "ro.server", realm = "weblogic.com") },
public class ExampleBean2 {
}
 
//specify origins.
@DiameterBean(
applicationId = 4,
origins = { @DiameterNode(host = "originserver", realm = "originserver.com"),
@DiameterNode(host = "ro.client", realm = "weblogic.com") },
public class ExampleBean3 {
}
 
//destinations specify both host and realm.
@DiameterBean(
applicationId = 4,
destinations = { @DiameterNode(host = "ro.server", realm = "weblogic.com") })
public class ExampleBean3 {
}
 
//destinations only specify host.
@DiameterBean(
applicationId = 4,
destinations = { @DiameterNode(host = "ro.server") })
public class ExampleBean4 {
}

//destinations only specify realm.
@DiameterBean(
applicationId = 4,
destinations = { @DiameterNode(realm = "weblogic.com") })
public class ExampleBean5 {
}
}

Filtering Observer Methods Based on Command Codes and Parameters

A Diameter bean may need to filter the messages based on the command code of the message. For example, if the Diameter bean wants to receive Session Terminated Answer (STA) and Credit Control Answer (CCA) messages on two different methods, it can do so by using the @DiameterObserver annotation. If the @DiameterObserver annotation is specified in the method, then the code injected by @DiameterObserver will be used by the Diameter stack (CDI) for delivering the message to the correct method.

If two methods have the same @DiameterObserver annotation, the Diameter bean selects the method where the parameter is the same type as the message.

Example 1-6 illustrates this behavior.

public void handleCCA(@Observes @DiameterObserver(code=272) CCA cca) {
}

public void handleAnswer(@Observes @DiameterObserver(code=272) Answer answer) {
}

public void handleSTA(@Observes @DiameterObserver(code=275) Answer answer) {
}

public void handleCCR(@Observes @DiameterObserver(code=272) CCR ccr) {
}

public void handleRequest(@Observes @DiameterObserver(code=272) Request request) {
}

public void handleMessage(@Observes Message message) {
}

In Example 1-6 the following filtering occurs:

• When a CCA message comes in, it is delivered to handleCCA() not handleAnswer(), because the handleCCA() parameter CCA matches the CCA message type exactly.

• When an Answer message (not a CCA) with the command code 272 comes in, it it is delivered to the handleAnswer() method.

• When an STA message comes in, it is delivered to the handleSTA() method.

• When a CCR message comes in, it is delivered to the handleCCR() method rather than the handleRequest() method.

• When a request message (not a CCR) with command code 272 comes in, it is delivered to the handleRequest() method.

• When other Diameter messages come in, they are delivered to the handleMessage() method.

Dynamic Configuration

Since the host and realm values of a @DiameterNode may need to be updated frequently, Converged Application Server leverages Java Enterprise Edition Environmental Entries, and lets you define them as variables, placing their values in SIP application deployment descriptors, such as sip.xml, or web.xml rather than hard coding them in source code. The deployment descriptors can be then be modified without requiring an application recompile. Alternatively, you can use WebLogic deployment plans to modify environmental variables.

In a @DiameterNode if host or realm is defined using the pattern, ${xxxx}, the xxxx is treated as a variable name. That variable name is matched to env-entry-name elements in sip.xml or web.xml, and, when a match occurs, the associated value is returned, replacing ${xxxx}.

The host or realm variable can defined by using letters, digits, hyphen, dots and underscore character.

Example 1-7 is a typical sip.xml configuration file with two env-entry elements containing env-entry-name child elements.

<?xml version="1.0" encoding="UTF-8"?>
<sip-app xmlns="http://www.jcp.org/xml/ns/sipservlet" xmlns:javaee="http://java.sun.com/xml/ns/javaee">
  <app-name>FooServlet</app-name>
  <javaee:display-name>diameter abstract API Test</javaee:display-name>
  <distributable />
  <javaee:env-entry>
    <javaee:description>peer server host name</javaee:description>
    <javaee:env-entry-name>peer-server</javaee:env-entry-name>
    <javaee:env-entry-type> java.lang.String </javaee:env-entry-type>
    <javaee:env-entry-value>ro.client</javaee:env-entry-value>
  </javaee:env-entry>
  <javaee:env-entry>
    <javaee:description>peer server realm</javaee:description>
    <javaee:env-entry-name>peer-realm</javaee:env-entry-name>
    <javaee:env-entry-type> java.lang.String </javaee:env-entry-type>
    <javaee:env-entry-value>example.com</javaee:env-entry-value>
  </javaee:env-entry>
</sip-app>

In Example 1-8, the host value for @DiameterNode is defined as ${peer-server}. To retrieve the value of peer-server from sip.xml in Example 1-7, the env-entry elements are searched for an env-entry-name element that matches peer-server. The match in this case is the env-entry-value, ro.client. Likewise, the realm value, peer-realm from ${peer-realm} matches the env-entry-name, peer-realm, which then returns the env-entry-value, example.com.

@DiameterBean
(applicationId= 4, 
  peers= {@DiameterNode (host = "${peer-server}", realm ="${peer-realm}")})
public class ExampleBean { 
}

The realm and host values of @DiameterNode can also be changed using a WebLogic deployment plan.

Example 1-9 illustrates a WebLogic Deployment Plan file, plan.xml.

<?xml version='1.0' encoding='UTF-8'?>
<deployment-plan xmlns="http://xmlns.oracle.com/weblogic/deployment-plan" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://xmlns.oracle.com/weblogic/deployment-plan http://xmlns.oracle.com/weblogic/deployment-plan/1.0/deployment-plan.xsd">
  <application-name>thirdpartyprotocol</application-name>
  <variable-definition>
    <variable>
      <name>new_peer-server</name>
      <value>ro.client2</value>
    </variable>
    <variable>
      <name>new_peer-realm</name>
      <value>example.com2</value>
    </variable>
  </variable-definition>
  <module-override>
    <module-name>thirdpartyprotocol.war</module-name>
    <module-type>war</module-type>
    <module-descriptor external="false">
      <root-element>web-app</root-element>
      <uri>WEB-INF/web.xml</uri>
    </module-descriptor>
    <module-descriptor external="false">
      <root-element>sip-app</root-element>
      <uri>WEB-INF/sip.xml</uri>
      <variable-assignment>
        <name>new_peer-server</name>
<xpath>/sip-app/env-entry/[env-entry-name="peer-server"]/env-entry-value</xpath>
        <operation>replace</operation>
      </variable-assignment>
      <variable-assignment>
        <name>new_peer-realm</name>    <xpath>/sip-app/env-entry/[env-entry-name="peer-realm"]/env-entry-value</xpath>
        <operation>replace</operation>
      </variable-assignment>
    </module-descriptor>
  </module-override>
</deployment-plan>

In Example 1-9 two variables are defined, new_peer-server and new_peer-realm, which are then used to replace the env-entry-values in sip.xml after plan.xml is deployed. You can use the WebLogic Administration Console to specify a deployment plan for your application, or you can use the weblogic.Deployer to deploy an application with the -plan parameter:

java weblogic.Deployer -adminurl http://hostname:port -user username -password password -deploy -name application-name -source application-name.war -targets server-name -stage -plan plan.xml

Diameter Application Development Environment Configuration

This section describes requirements for compiling legacy Diameter applications as well as configuring Diameter nodes.

Middleware_Home/Oracle_Home/wlserver/sip/server/lib/

/Oracle/Middleware/Oracle_Home/wlserver/sip/server/lib/

/Oracle/Middleware/Oracle_Home/user_projects/domains/Diameter_domain/config/custom

Overview of the Diameter API

All classes in the Diameter base protocol API reside in the com.bea.wcp.diameter package. Table 1-1 describes the key classes, interfaces, and exceptions in this package.

In addition to these base Diameter classes, accounting-related classes are stored in the com.bea.wcp.diameter.accounting package, and credit-control-related classes are stored in com.bea.wcp.diameter.cc. See Chapter 4, "Using the Diameter Ro Interface API for Online Charging" and Chapter 3, "Using the Diameter Rf Interface Application for Offline Charging" for more information about classes in these packages.

Working with Diameter Nodes

In order to access a Diameter application, a deployed application (such as a SIP Servlet) must obtain the Diameter Node instance and request the application. Example 1-10 shows the sample code used to access the Rf application.

ServletContext sc = getServletConfig().getServletContext();
Node node = sc.getAttribute("com.bea.wcp.diameter.Node");
RfApplication rfApp = (RfApplication) node.getApplication(Charging.RF_APPLICATION_ID);

Implementing a Legacy Diameter Application

All Diameter applications must extend either the base Application class or, for client applications, the ClientApplication class. The model for creating a Diameter application is similar to that for implementing Servlets in the following ways:

• Diameter applications override the init() method for initialization tasks.

• Initialization parameters configured for the application in diameter.xml are made available to the application.

• A session factory is used to generate new application sessions.

Diameter applications must also implement the getId() method to return the proper application ID. This ID is used to deliver Diameter messages to the correct application.

Applications can optionally implement rcvRequest() or rcvAnswer() as needed. By default, rcvRequest() answers with UNABLE_TO_COMPLY, and rcvRequest() drops the Diameter message.

Example 1-11 shows a simple Diameter client application that does not use sessions.

public class TestApplication extends ClientApplication {
  protected void init() {
    log("Test application initialized.");
  }
  public ApplicationId getId() {
    return ApplicationId.BASE_ACCOUNTING;
  }
  public void rcvRequest(Request req) throws IOException {
    log("Got request: " + req.getHopByHopId());
    req.createAnswer(ResultCode.SUCCESS).send();
  }
}

Working with Diameter Sessions

Applications that perform session-based handling must extend the base Session class to provide application-specific behavior for managing requests and answering messages. If you extend the base Session class, you must implement either rcvRequest() or rcvAnswer(), and may implement both methods.

The base Application class is used to generate new Session objects. After a session is created, all session-related messages are delivered directly to the session object. The Converged Application Server container automatically generates the session ID and encodes the ID in each message. Session attributes are supported much in the same fashion as attributes in SipApplicationSession.

Example 1-12 shows a simple Diameter session implementation.

public class TestSession extends Session {
  public TestSession(TestApplication app) {
    super(app);
  }
  public void rcvRequest(Request req) throws IOException {
    getApplication().log("rcvReuest: " + req.getHopByHopId());
    req.createAnswer(ResultCode.SUCCESS).send();
  }
}

public class TestApplication extends Application {
  ...
  public TestSession createSession() {
    return new TestSession(this);
  }
}

TestSession session = testApp.createSession();
Request req = session.creatRequest();
req.sent();

Working with Diameter Messages

The base Message class is used for both Request and Answer message types. A Message always includes an application ID, and optionally includes a session ID. By default, messages are handled in the following manner:

1. The message bytes are parsed.

2. The application and session ID values are determined.

3. The message is delivered to a matching session or application using the following rules:

   1. If the Session-Id AVP is present, the associated Session is located and the session's rcvMessage() method is called.

   2. If there is no Session-Id AVP present, or if the session cannot be located, the Diameter application's rcvMessage() method is called.

   3. If the application cannot be located, an UNABLE_TO_DELIVER response is generated.

The message type is determined from the Diameter command code. Certain special message types, such as RAR, RAA, ACR, ACA, CCR, and CCA, have getter and setter methods in the Message object for convenience.

static final Command TCA = Command.define(1234, "Test-Request", true, true);

Working with AVPs

Attribute Value Pair (AVP) is a method of encapsulating information relevant to the Diameter message. AVPs are used by the Diameter base protocol, the Diameter application, or a higher-level application that employs Diameter.

The Avp class represents a Diameter attribute-value pair. You can create new AVPs with an attribute value in the following way:

Avp avp = new Avp(Attribute.ERROR_MESSAGE, "Bad request");

You can also specify the attribute name directly, as in:

Avp avp = new Avp("Error-Message", "Bad request");

The value that you specify must be valid for the specified attribute type.

To create a grouped AVP, use the AvpList class, as in:

AvpList avps = new AvpList();
avps.add(new Avp("Event-Timestamp", 1234));
avps.add(new Avp("Vendor-Id", 1111));

static final Attribute TEST = Attribute.define(1234, "Test-Attribute", 0, Attribute.FLAG_MANDATORY, Type.INTEGER32);

Creating Converged Diameter and SIP Applications

The Diameter API enables you to create converged applications that utilize both SIP and Diameter functionality. A SIP Servlet can access an available Diameter application through the Diameter Node, as shown in Example 1-13.

ServletContext sc = getServletConfig().getServletContext();
Node node = (Node) sc.getAttribute("com.bea.wcp.diameter.Node");
RfApplication rfApp = (RfApplication) node.getApplication(Charging.RF_APPLICATION_ID);

Session session = app.createSession();
session.setListener(new SessionListener() {
  public void rcvMessage(Message msg) {
    if (msg.isRequest()) System.out.println("Got request!");
  }
});