Using an EJB3 Interceptor in Seam

For one of the demos for the NEJUG presentation we integrated the JPetStore (Spring based) and the DVDStore (Seam based) with JBossESB. The idea is that when orders are placed in either store the orders are processed in some ESB based Order Processing Service, using jBPM for the Orchestration. Here I want to show what you need to do to intercept a the order when the user hits the 'confirm' button in the Seam based DVD Store. For this we use an EJB3 interceptor. The beauty of this solution is that no code changes are needed in the DVD Store itself.

1. Modify the ejb-jar.xml
First we need to add some configuration to the ejb-jar.xml, as shown in Figure 1.


Figure 1. Add the interceptor to the ejb-jar.xml


So first we define the interceptor class by referencing

com.jboss.dvd.seam.CheckoutInterceptor

, next we need to specify when this class should be called, which is done by adding the second piece of xml which specifies the bean name for which the interceptor should fire. Here we want it to fire when the

CheckoutAction

is called.

2. Add the interceptor class

The interceptor class itself looks like

package com.jboss.dvd.seam;

import javax.interceptor.AroundInvoke;
import javax.interceptor.InvocationContext;

public class CheckoutInterceptor {

    @AroundInvoke
    public Object sendOrderToESB(InvocationContext ctx) throws Exception {

        System.out.println("*** Entering CheckoutInterceptor");
        Object target = ctx.getTarget();
        //Just making sure
        if (target instanceof CheckoutAction) {
            if (ctx.getMethod().getName().equals("submitOrder")) {
                System.out
                        .println("We will send the following completedOrder object to ESB");
                Order completedOrder = ((CheckoutAction) target).currentOrder;
                Customer customer = ((CheckoutAction) target).customer;
                completedOrder.setCustomer(customer);
                System.out.println("Completed Order= " + completedOrder);
            }
        }
        try {
            return ctx.proceed();
        } finally {
            System.out.println("*** Exiting CheckoutInterceptor");
        }
    }
}

Figure 2. The CheckoutInterceptor Code

And that is all there is to it. In the interceptor we check which method is called, and if it is the

submitOrder

method we print out the order. In the demo we added code to serialize the order to XML, and then dropped in onto a gateway Queue, on its way to the ESB.