Patterns: Implementing Self-Service in an SOA Environment

324 Patterns: Implementing Self-Service in an SOA Environment

Rational Application Developer provides support for developing mediation

handler code and adding mediation handlers to the J2EE deployment

descriptors.

10.6.1 Create the router mediation

The router mediation performs the following tasks:

򐂰 Examines the delivery type specified in the incoming message.

򐂰 If the type is Home, no action is required. The forward routing path of the

message is already set to the HomeDelivery Web service.

򐂰 If the type is Business, it modifies the forward routing path of the message to

send it to route it to the BusinessDelivery Web service.

򐂰 If the type is All, it:

– Clones the message.

– Modifies the forward routing path of one message to BusinessDelivery.

– Modifies the reverse routing path of both messages to a queue destination

(for aggregation).

Use the following steps to create the router mediation:

1. Build the code:

a. Create a simple project called RoutingMediations.

b. Right-click the RoutingMediations project and select Add → Others →

Java Class. Name the class RoutingMediation.

c. Implement the MediationHandler interface and add the routing code in the

handle method (see “RouterMediation code” on page 325).

d. Create a JAR file from the package and call it RoutingMediations.jar.

2. Create the mediation EJB:

a. Create an EJB project called RoutingMediationsEJB with an EAR file

name of RoutingMediationsEJBEAR.

b. Drag and drop RoutingMediations.jar to the Utility JARS folder in

RoutingMediationsEJBEAR.

3. Define the mediation handler in the EJB deployment descriptor:

a. Expand the RoutingMediationsEJB project in the navigator and double-

click Deployment Descriptor.

b. Select the Mediation Handler tab.

Chapter 10. Web services scenario 325

c. Click the Add button and enter RoutingHandler as the name. Enter

myPackage.RoutingMediation as the handler class.

d. Save the descriptor.

RouterMediation code

The handle() method (Example 10-3) is invoked by the arrival of a message on

the mediated port. It gets a handle to the MessageContext interface, which

provides methods to manage a property set. Message context properties enable

handlers in a handler chain to share processing related state. The context

properties used for the mediation (Table 10-3 on page 350) are defined when you

prepare the runtime for mediation.

The handle() method casts the message context to SIMessageContext. This is

the object that is required on the interface of a mediation handler. In addition to

the context information that can be passed from one handler to another, it can

return a reference to an SIMessage and an SIMediationSession. The SIMessage

is the service integration bus representation of the message being processed by

the MediationHandler. An SIMessage contains message properties, header

contents, routing path, and the message body. The SIMediationSession is a

handle to the runtime resources.

Example 10-3 RoutingMediation part 1

public class RoutingMediation implements MediationHandler {

public boolean handle(MessageContext context) throws MessageContextException {

String businessDestination=(String)context.getProperty("businessDestination");

SIMessageContext ctx =(SIMessageContext)context;

SIMediationSession session = ctx.getSession();

String busName = session.getBusName();

SIMessage message = ctx.getSIMessage();

SIMessage newMessage=null;

List frp=null;

SIDestinationAddressFactory factory =

SIDestinationAddressFactory.getInstance();

Next (Example 10-4 on page 326), we retrieve the DataGraph object from the

message. The message is inspected to find the type of delivery the customer has

requested-Home, Delivery, or All (both).

Note: The entire source code for the router mediation can be seen by

downloading the sample application. The code is in the RoutingMediations.jar

in the RoutingMediationsEJB project.

326 Patterns: Implementing Self-Service in an SOA Environment

Example 10-4 RoutingMediation part 2

try {

DataGraph graph = message.getDataGraph();

DataObject rootNode = graph.getRootObject();

DataObject infoNode = rootNode.getDataObject("Info");

// Get the body node

DataObject bodyNode = infoNode.getDataObject("body");

// Get the data object for the first part of the body

DataObject part1Node = bodyNode.getDataObject("parameters");

// Determine the delivery option requested by the customer (Home, Business, All)

String ticker = part1Node.getString((String)context.getProperty("type"));

If the user has requested both home and business delivery (type=All), the next

section (Example 10-5) clones the message.

The original message has a forward routing path that will send it to the

HomeDelivery service. The forward routing path in the cloned message is set to

send it to the BusinessDelivery service, using the businessDestination context

property.

The reverse routing path for both messages is changed to the value of the

DeliveryResponseDestination context property. In this case, the property is set to

a destination queue defined on the bus. Once the forward and reverse routing

paths are properly set, the new message is sent.

Example 10-5 RoutingMediation part 3

if (ticker.equalsIgnoreCase((String)context.getProperty("ALL")))

{

newMessage = (SIMessage)message.clone();

List frp1= newMessage.getForwardRoutingPath();

newMessage.setApiMessageId(message.getApiMessageId());

newMessage.setDataGraph(message.getDataGraph(),message.getFormat());

SIDestinationAddress businessDestAddress = factory.

createSIDestinationAddress(businessDestination,busName);

frp1.add(businessDestAddress);

newMessage.setForwardRoutingPath(frp1);

List reverse1 = newMessage.getReverseRoutingPath();

System.out.println("Reverse Routing Path -- "+reverse1);

SIDestinationAddress deliveryResponseAddress = factory.