Web Service to Grid Service

The Globus Toolkit 3.0 (GTK3.0) provides a number of tools that can be used to convert an existing implementation of a Web Service into a Grid Service. For this purpose only a JAR of all the classes implementing the Web Service is required. In addition to the implementation code, an antfile must be created to use the tools provided in GTK3.0.

As an illustration, we shall use calculator.jar and build.xml. calculator.jar consists of the following classes:
The conversion of an existing Web Service to a Grid Service can be done as follows:

Step 1: Generate Grid Service Code

Existing Java code of a Web Service can be exposed as a Grid Service by compiling and archiving it into a JAR file. This JAR file is run through the createBottomUpGridService tool in GTK3.0 to automatically generate the stubs, the service locators, the deployment descriptor fragment, and an operation provider that delegates its calls into the existing Java code.

For example, in build.xml we have the target named createBottomUpGridService which in turn calls the createBottomUpGridService tool within build-tools.xml in GTK3.0. Then the command
[purshah@danube mytry]$ ant createBottomUpGridService
is used which generates the output shown in build_output1.txt.

Step 2: Create a Grid Service Archive (GAR)

A gar target is available within build-tools.xml in GTK3.0 to archive all generated components into an archive file that serves as the unit of deployment.

For example, in build.xml, we have a target named bottomUpGar which in turn calls the gar tool within GTK3.0. Then the command
[purshah@danube mytry]$ ant bottomUpGar
is used and the corresponding output is shown in build_output2.txt.

Step 3: Deploy the Service

The deploy target provided in GTK3.0 (not in the build.xml that we have written) is used to deploy the GAR that is generated in the previous step into a Grid Service hosting environment.

In <gtk3.0> the following command line call must be made: ant deploy -Dgar.name=<path to GAR created in previous step>

For example, in order to deploy our Grid Service, the following command is used
[purshah@danube test_install_dir]$ ant deploy -Dgar.name=/home/purshah/test_install_dir/mytry/calculator/CalculatorService.gar
and the corresponding output is shown in build_output3.txt.

Step 4: Check the new Grid Service

In order to check the new Grid Service, start the container using ant startContainer in <gtk3.0>. It should list the Grid Service that was deployed in the previous step.

Step 5: Creating a Client

In order to create a client for this Grid Service, steps to be followed are similar to the steps taken to create a client for the sample Grid Services in GTK3.0. These steps are described here.

For example, a CalcAdder client for the Calculator Service is created. The use of this client is shown below:

[purshah@danube client]$ java org.globus.ogsa.client.CreateService http://localhost:8080/ogsa/services/services/DefaultNamespace/CalculatorImplProviderFactoryService calc1
Termination Time: infinity
Created service with reference:
<definitions name="CalculatorImpl" targetNamespace="http://DefaultNamespace/service" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:calculatorimplbinding="http://DefaultNamespace/bindings" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"><import location="http://156.56.104.61:8080/schema/services/CalculatorImpl_bindings.wsdl" namespace="http://DefaultNamespace/bindings"/><service name="CalculatorImplService" xmlns:gsdl="http://ogsa.globus.org/"><gsdl:instanceOf handle="http://156.56.104.61:8080/ogsa/services/services/DefaultNamespace/CalculatorImplProviderFactoryService/calc1" xmlns=""/><gsdl:instanceOf handle="http://156.56.104.61:8080/ogsa/services/instance" xmlns=""/><port binding="calculatorimplbinding:CalculatorImplSOAPBinding" name="CalculatorImplPort"><soap:address
location="http://156.56.104.61:8080/ogsa/services/services/DefaultNamespace/CalculatorImplProviderFactoryService/calc1"/></port></service></definitions>
[purshah@danube calculator]$ java client.CalcAdder http://localhost:8080/ogsa/services/services/DefaultNamespace/CalculatorImplProviderFactoryService/calc1 1 2
Sum:3
[purshah@danube calculator]$ java client.CalcAdder http://localhost:8080/ogsa/services/services/DefaultNamespace/CalculatorImplProviderFactoryService/calc1 1 4
Sum:5


For additional details on the use of tools within Globus Toolkit 3.0 to create Grid Services please refer this guide.