Linux
In today's economy, many companies are looking for ways to cut costs while still offering an exceptional customer experience by using the Linux operating system. Although it has been around for almost 10 years, Linux only started to really get some serious consideration in the past few years. Looking beyond its unbeatable license agreement, some speculate that Linux's recent surge in popularity stems from its attractiveness as a great alternative method for developing different types of applications – including Web services.

As you start preparing your Web services development environment, carefully consider your installation needs before choosing a Linux distribution. Each distribution provides different package formats (e.g., .zip, .deb, .jar, and .tar files), and not every software package is readily available for every Linux distribution. In some cases only older versions of a given package might be available. The package type you choose can impact your ease of installation and configuration.

Among the many distributions of Linux, the top three are:

Web Services
The next time someone asks you what a Web service is, you can explain that it is simply a self-contained software component that sends and receives XML data across the Internet. Web services typically use two XML standards: Simple Object Access Protocol (SOAP) to define the XML message, and Web Services Description Language (WSDL) to describe the Web service interface.

In a simple Web services scenario, an application sends a request to a service at a given URL using SOAP over HTTP. The service receives the request, processes it, and returns a response. Take the example of a weather forecast service, shown in Figure 1. The weather forecast service requests the current weather of a specified location, and the Web service response returns the forecast. This is the simplest form of a Web service because the response is sent almost immediately, and the request and response are both parts of the same method call.

Now let's look at a more realistic scenario. ABC Company contracts with a software consulting firm to develop an order entry application for them. The order entry application needs to communicate with a parts information system on a mainframe to access information when orders are entered. In order to perform the integration with the mainframe, ABC Company has its developers create a software component that exposes data on the mainframe as a Web service. The software consulting firm then creates the order entry application to access the mainframe via this Web service.

In this scenario, the Web service provides the following benefits:

Starting to see some of the possibilities that Web services offer? If any of the follow- ing situations sound familiar, consider putting Web services into action in your own organization:

Web Services on Linux
Because you can now choose from numerous Linux-compatible tools to help you, developing Web services on Linux should no longer sound so scary (see Figure 2). Ready to get started? To get your Web services designed and running, you need to choose:

Selecting a Web Services Platform
Remember that Web services are simply components that send and receive XML data across the Internet. Encoding and decoding data between the SOAP format and the underlying business objects is what makes Web services development difficult. While a SOAP processing engine or a SOAP server can be written from scratch, it is better to invest in a Web services platform to manage the Web services. Essentially, a SOAP server is an XML processor and an HTTP server (see Figure 3).

Before you select your Web services platform, become familiar with the requirements for a Web services platform. These include:

Before we look at specific Web services platforms, you should also know that Web services development requires three basic steps. These are:

1. Create the Web services interface
2. Package and deploy the Web service
3. Invoke the Web service

Here are two popular Web services platforms:

Monitoring the Service
Both Axis and BEA incorporate tools to help you monitor your Web services. Axis provides the tcpmon utility class that listens for connections on a given port on the local host and forwards incoming messages to another port on another server. By inserting itself between the two ports, tcpmon shows you all incoming and outgoing SOAP messages. Similarly, WebLogic Workshop provides you with a view of the SOAP messages. The two approaches differ in that the Apache Axis utility makes you configure tcpmon, while WebLogic Workshop embeds this capability within its user interface.

Testing the Service
When testing a Web service, you must have well-designed tests – especially if the service will be distributed and leveraged by other divisions, customers, suppliers, and partners. And testing a Web service presents a particular challenge because it lacks a user interface. Unlike Web-based applications that contain a presentation layer, Web services typically expose an XML request/response interface. Fortunately, you can choose from among several automated testing tools to help simplify your Web services testing process on Linux.

A couple of the tools that we evaluated and recommend include:

Managing the Service
In order to get the most out of Web services, you must be able to actively manage and control the new capabilities that come along with them. HP OpenView offers application management for most software running today. The new Web Services Management Engine (WSME) is already available for capturing Web services transactions, actively managing Web services over WSDL/SOAP, and enabling provisioning, user profile registration, realtime SLA enforcement, access control, subscription management and metering for prepaid billing. WSME can be deployed either as an endpoint on a Web service platform, or as a control point in front of a farm of Web service platforms. WSME can also natively manage J2EE or .NET Web services deployed behind or beyond the firewall.

Looking forward, new manageability needs will continue to grow, as will the need for different operating environments such as Linux, hp-ux, and Windows to coexist in the same Internet infrastructure. As a result, organizations will demand tools that provide increasingly tight, integrated management for these components in order to achieve optimum costs and increase service levels at the same time.

See Table 1 for a list of the tools available for Web services development along with the versions of Linux that each supports.

Conclusion
Web services offer solutions to deal with the changes, flexibility needs, and firewall issues that your organization faces. Building your Web services on Linux makes sense; now you have an overview of a wide variety of tools to help develop, monitor, and test your Web services. Put the best practices outlined in this paper to use and see how Web services can help your organization design sound integration tasks and transform its business processes.