8.10 Using Velocity For Scripting

8.10.1  Local Methods Compared to Local Macros

To be honest, the implementation is a hack for now ... but a useful one and it gets the job done.

We tend to write some complex jobs using JeeWiz/Velocity because it saves having to learn or remember another script environment. In addition, the JeeWiz environment provides significant features for scripting that help in specific ways:

1. Easy file handling: readFileAsString/Lines/XML, writeStringToFile
2. Complex string handling made easy. e.g. see the helper methods: getPieces*, CSV handling, exciseString(), ordering using TreeMap.
3. Access to Java classes for specialised processing.
4. XML process: the convert() feature for filtering and changing element tags, utilities for writing attributes and CDATA, formatXML() for easy reformatting of XML. Our (hard-won) experience is that, compared to XSL-T, JeeWiz is much faster to develop and runs dramatically faster.
5. Easy to define methods (normal JeeWiz #method()...#end)
6. divert/revert for massaging output text; easy to write reports.

8.10.2  jwscript batch job

You can implement extensions to the scheme described here by copying and amending jeewiz/external/ant1.7.0/bin/jwscript.bat (but best to keep it in the Ant directory).

8.10.3  Syntax and Operation

1. The specification. You do not need to input a model/specification to a script.
   • If you do not input a specification, "" is used; this is taken from the file jeewiz/resources/jwscript/specification/assembly.xml.
   • If you want to input a specification, specify "-x" and the file as the first arguments There is no default extension (like ".xml"). This must be an XML format file. Any valid XML file is allowed: there is no specific meta-model checking because this uses the "any" to run, which will accept any valid XML.
2. The script file. A Velocity script (by convention with a ".vs" extension) must be specified. This is what will be run! The script is copied to jeewiz/resources/jwscript/control/start.vm, which will automatically run with the top component (i.e. the root XML element) as its context.
3. Arguments Arguments (intended for the script) and Ant switches (like '-v') are specified after the scriptfile. They can be in any order. The Velocity variable $args is always defined for a script. It is an ArrayList. If no arguments are specified, $args is empty - size()==0. If arguments are specified, they are added to the ArrayList in the order they appear on the command line. The first argument is accessed by $args.get(0); the second by $args.get(1).
4. For example, currently it is not possible to use local files (i.e. in the same directory as the Velocity script file) in #parse(). These will have to be copied into the target area for the script file (i.e. make it a peer of jeewiz/resources/jwscript/control). And if you do this, you might want to change the location to your own specific subdirectory of jeewiz/examples/any rather than use the jwscript/ directory. This is straightforward to do in your own enhanced batch job.

8.10.4  Piping input

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