Tutorials : Deliver On-the-Fly Mapping Services to Your Rich Desktop Java Application, Part 1 :

Generation of a Tile URL Using Rhino

The SwingX-WS project provides the TileFactoryInfo class, which you'll extend in the XMLTileFactoryInfo class. Once again, click here for a complete link to the XMLTileFactoryInfo class and all its supporting code. While the SwingX-WS project's TileFactoryInfo class has a general purpose getTileUrl method, this method is not adequate for all situations. Increasing the generality of this class is one option, but you'd still be faced with the issue of how to stay current with the inevitable explosion of free mapping services without recompiling your client's Java code. That problem is solved if you configure the TileFactoryInfo class from your XML and execute the BuildURLFunction element's JavaScript in Java.

Java SE 6 includes the Scripting for the Java Platform API, which you could have used, and Java SE scripting is based on Mozilla's Rhino. However, in order to maintain backward compatibility with Java SE 5, you'll instead use Mozilla's Rhino directly. Listing 4 shows exactly how to compile and call the Javascript.

In Listing 4, the buildURLFunctionJS member is the Java representation of your JavaScript and it is compiled only if necessary. Next, the JavaScript call is executed. An unchecked exception will be thrown if the script cannot be compiled or if there is a problem with the call. Errors, if they occur, indicate that the JavaScript has problems and the programmer should review the BuildURLFunction element in the XML.

You now have an XML data configuration that describes how to request a tile from a tile server. You have a way to parse the XML and also a way to execute the BuildURLFunction element's JavaScript function in your Java code. Altogether, you have a way to stay current with the inevitable explosion of free mapping services without recompiling your client's Java code.

I've made the code for Part 2 of this series available as an Eclipse project. Depending on your Eclipse environment, you may need to change the build path to use a specific jdk1.5+ installed on your system. Alternately, there is an Ant build.xml file to build and run the project.

If you already have your own rich Java mapping client, then the code in Part 2 of this series will be a good starting point for adding the dynamic delivery of mapping services mechanism to your existing application. In the final part of this series, you'll build on this code and use the SwingX-WS project to complete your rich Java application.

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