Web Services Simulator
The value of simulation for ensuring the smooth implementation of IT projects is clear
. With that said, a Web Services Simulator is an indispensible tool that can be put to a variety of uses during all the phases of SOA implementation. I want to illustrate the several uses of such a simulator while describing a valid use case. There were two separate teams responsible for implementing the Front End Portal Layer and the web services layer for exposing the backend Legacy Interfaces. The Portal team had all the wireframes ready for implementationsay by July. However, the wireframes and screen transitions could not be tested without the actual web services that supported each screen. The team that was responsible for implementing the web services could deliver the first service by October at the earliest. Hence the resulting time lag of nearly 3 months where the Portal team would not be able to proceed with their work.
Solution Options:
It was decided to use a web services simulator to simulate the exact functions of a web services backend. A couple of commercial products were evaluated, but they would not fit the bill due to the following:
- The development license per seat was quite cost prohibitive especially given there were 10-12 developers in the team
- The out of box functionality provided by the tools did not exactly suit the client's needs and a lot of customization would still be required
- The XML payloads were quite large and complex in nature and automated tools were needed for generating these.
Given these roadblocks, it was decided to build a custom Simulator Framework and the tools needed to generate the sample XML payloads.
Web Services Invocation Framework
The web services invocation framework was built as a separate framework to enable easy invocation of services from the client side by any client. In this particular case, the client was the Portal.
The following factors influenced the design of the web services client invocation framework.
- The details of the actual web services should be abstracted out from the user.
- Any client should be able to invoke a given web service using the simplest mechanism possible; for instance, a web service can be invoked by just using this one line command:
Object response = wsFramework.execute(ws.USER_ADDRESS, insReq);
- The framework should be so generic that other application components such as Exception Handling, Auditing, Messaging, Input/Output(File,DB) etc. would easily be pluggable into the existing framework alongside the web services components.
The web services simulator was designed and implemented based on the design of this invocation framework. Here are some of the salient features of the web services invocation framework:
- The invocation framework is a very generic framework and is driven through configuration files.
- Any new service to be invoked will not need any code change to the core framework itself. The service is added as a new definition to the XML configuration file.
- The framework itself uses open source web services libraries like Axis2 and JAX-WS to do the actual service invocation.
- The framework classes wrap around these underlying open source libraries and provide all the necessary input parameters such as input payload, authentication data etc.
The framework had several other components incorporated into it such as Exception Handling, Auditing, File and DB Access.
Web Services Accelerators and Tools
Infogain has a very rich library of such tools that are provided, in most cases, free of cost to the clients and are used as Accelerators to jump start and reduce the implementation cycle times for an SOA implementation. Some of the tools described in this article are the web services and J2EE application framework, the web service simulator and the XML file generation tools.
Web Services Simulator
By: tajinder
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