Chapter 14: Web Services and Servlet Agents

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Overview

Most of this book has focused on how we can use servlets as web server components that provide services to clients. For example, a servlet might be responsible for the presentation of information to a client, perhaps by generating HTML that is rendered by a browser. We've also seen how servlets can act as clients to data sources that contain information that the servlet needs to build its response.

In this chapter we're going to look at how servlets can act as clients to web services. Then we'll look at how we can use such servlets to act as agents on our behalf. For example, a servlet agent could execute a web service on a regular basis in order to update an internal table of exchange rates.

In particular, we'll look at how we can:

• Generate and consume the messages used by web services

• Create and deploy web services using Apache SOAP

• Invoke web services and retrieve information from them

• Create servlet agents that can collect, cache, and aggregate information from web services

To do justice to web services and their associated technologies would require a book of its own. We're going to stick to looking at how web services are tools to be used by servlets. A more general discussion of how to create and use web services can be found in Professional Java Web Services (ISBN: 1-861003-75-7).

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