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A Simple Introduction to Web Services Using Flickr Andrew Mertz Associate Professor of Computer Science Department of Mathematics and Computer Science Eastern Illinois University Charleston, IL 61920 [email protected] Many programs use web services to store and access data. Such programs can take advantage of the fact that often web applications/sites provide developer APIs to programmatically access their services. While introductory Computer Science classes usually do not include web services as a central topic, giving a high level overview of them can provide an engaging, relevant, and familiar way of expanding on GUI design, networking, threading, parsing, and the like. This discussion will focus on building a simple client for retrieving public images from Flickr. Flickr (www.flickr.com) is a photo and video sharing site that also functions as an online community. With more than a million pictures uploaded daily and free accounts including one terabyte of storage, many students are already familiar with Flickr or similar web services. Like many such services, Flickr provides a nice set of APIs that developers can access (www.flickr.com/services/api/) and provides API keys on request. The sample client (implemented in Java, but adaptable to other languages) allows users to: enter search strings in a text field, view results of a search as a list image thumbnails, and select a thumbnail image to load a larger version in the primary panel. To this end students see how to: encode URLs, parse JSON (or XML depending on preference), use threads to keep the program responsive, indicate to the user that a long operation is in progress, work with JLists, and read responses from the network (noting how similar it is to reading from a file). When completed the students have a program they are often eager to show others and extend. Thus, there are natural follow-up assignments using Flickr APIs other than search (such as comments or favorites), to use other services such as Google Static Maps, or to combine different services into something new.
