Web applications and web services - OSGi in Action

Java Reference

In-Depth Information

CONFIGURING THE DISTRIBUTION PROVIDER FOR DISCOVERY

The Remote Services specification doesn't explicitly define how discovery is imple-

mented, only how it should behave. The Apache CXF Distributed OSG i implementa-

tion provides discovery based on the Apache Hadoop Zookeeper project ( http://

hadoop.apache.org/zookeeper/ ) , but its usage is beyond the scope of this topic.

Luckily, Apache CXF Distributed OSG i also provides a static version of discovery based

on the Remote Services Admin Endpoint description from the R4.2 Enterprise specifi-

cation. With this approach, the discovery process is directed by XML files contained in

bundles installed in the framework. The following listing shows the XML that

describes the StockProvider service, which is nearly identical to the configuration for

publishing the service.

Listing 15.12 XML discovery file for the StockProvider service for Apache CXF

<service-descriptions xmlns="http://www.osgi.org/xmlns/sd/v1.0.0">

<service-description>

org.apache.cxf.ws

</property>

http://localhost:9090/stockprovider

</property>

</service-description>

</service-descriptions>

For this example, package this file in OSGI-INF /remote-service/remote-services.xml of

a new bundle called stockprovider-client-1.0.jar. You define the interface that the dis-

covered service will provide B . Then you provide the configuration entries needed by

the distribution provider to bind to the remote service into the OSG i service registry C .

In this example, this new bundle is purely for configuring the discovery process, so it

only contains this XML file.

That's all there is to it. The service is automatically published into the OSG i service

registry; you can look it up and invoke methods on it, which results in remote method

invocations being sent using SOAP to the server proxy created in the remote JVM .

You now know how to provide and consume remote services. Let's wrap up this

example by seeing how to use this service in the stock-watcher application.

Defines

provided

service

interface B

Specifies configuration

information C

USING YOUR WEB SERVICE

It's time to see the updated stock-watcher application in action. Go into the

chapter15/webservice/ directory of the topic's companion code. Type ant to build

the example and java -Dorg.osgi.service.http.port=8081 -jar launcher.jar

bundles/ to execute it. Doing so starts the remote StockProvider service.

Now you need to start the stock-watcher application. In a separate command shell,

go into the chapter15/webservice-client/ directory of the companion code. Type ant

to build the application and java -jar launcher.jar bundles/ to start it. Browse to

OSGi in Action

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