Sunday, August 2, 2009

Example: Spring Integration + Spring DM OSGi + Spring Remoting

I have just come up with a example for Spring integration along with OSgi.

I basically have 4 bundles

1. Exchange bundle which has definitions of channels

This bundle is spring integration aware, and hence has channel definitions in it.

Channel definition.

<publish-subscribe-channel id="login"/>

This channl is wrapped around a gateway and exposed as a OSGi service.This is to ensure that the event generating bundle is unaware of spring integration apis

Wrapping channel around gateway

<gateway id="loginProxy" default-request-channel="login"
service-interface="" />

Exposing gateway as OSGi service

<osgi:service id="loginChannel" ref="loginProxy"
interface="" />

Also the channel is directly published as a OSGi service for listener listening to it.

<osgi:service id="loginAnnouncementsChannel" ref="login"
interface="" />

2. Login bundle - bundle which generate login event and publishes it using gateway.

Accepting the Gateway from the exchange bundle as a OSgi service

<osgi:reference id="eventPublisher"

This bundle generates periodic events using a spring timer task as shown below

<bean id="logineventGenerator" class="">
<property name="eventPublisher" ref="eventPublisher"></property>

<bean id="loginTask" class="org.springframework.scheduling.timer.ScheduledTimerTask">
<property name="period" value="10000" />
<property name="timerTask" ref="logineventGenerator" />

<bean id="timerFactory" class="org.springframework.scheduling.timer.TimerFactoryBean">
<property name="scheduledTimerTasks">
<ref bean="loginTask" />

Timer Task class generating events

public class LoginEventGenerator extends TimerTask {

IEvent eventPublisher;

public void setEventPublisher(IEvent eventPublisher) {
this.eventPublisher = eventPublisher;

public void run() {
System.out.println("login event published");
eventPublisher.login("Logged In");


3. Pam-proxy bundle is a bundle which listens to the event using OSGi refered pub-sub-channel

When the message is obtained it makes a spring remoting call uisng remoting adaptors

Consumed OSGi service

<osgi:reference id="loginAnnouncementsChannel"

Activator which makes a remoting call when message is put on a channel

<si:service-activator input-channel="loginAnnouncementsChannel"

Channel which gets the spring remoting response
<si:channel id="responseChannel" />

Activator listening on the response
<si:service-activator input-channel="responseChannel"
method="handleResponse" />

ProxyFactory bean for making spring remoting call
<bean id="exampleService"
class="org.springframework.remoting.httpinvoker.HttpInvokerProxyFactoryBean" >
< property name="serviceUrl" value="http://localhost:8088/test/pamService" />
< property name="serviceInterface" value="com.pam.external.IExampleService" />

Response handler for the spring remoting call
<bean id="responseHandler" class="com.pam.proxy.sample.ResponseHandler" />

All the above bean can be avoided and instead we can use http-invoker inbound and outbound adaptors as explained in spring integration reference guide.

But i did not want the spring remoting hosting side to be unaware of spring integration.

Also i did not want to put any java code in the pam-proxy bundle.

4. Pam web bundle publishing a spring remoting service

<bean id="exampleProxy" class="com.pam.ExampleService" />

<bean name="/pamService"
<property name="service" ref="exampleProxy" />
<property name="serviceInterface" value="com.pam.external.IExampleService" />

Source Code Location :

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