Wednesday, 15 January 2020

Javascript in ANT

Earlier I wrote about an ANT script to scan JCA adapters files in your projects home, subversion working copy or github local repo.

In my current project we use sensors to kick-of message-archiving processes, without cluttering the BPEL process. I'm not sure if I would do that like that if I would do on a new project, but technically the idea is interesting. Unfortunately, we did not build a registry what BPEL processes make use of it and how. So I tought of how I could easily find out a way to scan that, and found that based on the script to scan JCA files, I could easily scan all the BPEL sensor files. If you have found the project folders, like I did in the JCA scan script, you can search for the *_sensor.xml files.

So in a few hours I had a basic sript. Now, in a second iteration, I would like to know what sensorActions the sensors trigger. For that I need to interpret the accompanying *_sensorAction.xml file. There for, based on the found sensor filename I need to determine the name of the sensor action file.

The first step to that is to figure out how to do a substring in ANT. With a quick google on "ant property substring", I found a nice stackoverflow thread, with a nice example of an ANT script defininition based on Javascript:
  <scriptdef name="substring" language="javascript">
    <attribute name="text"/>
    <attribute name="start"/>
    <attribute name="end"/>
    <attribute name="property"/>
       var text = attributes.get("text");
       var start = attributes.get("start");
       var end = attributes.get("end") || text.length();
       project.setProperty(attributes.get("property"), text.substring(start, end));

And that can be called like:
    <substring text="${}" start="0" end="20"   property=""/>
    <echo message="Sensor Action file: ${sensorAction.file.name1}"></echo>

The javascript substring() function is zero-based, so the first character is indexed by 0.
Not every sensor file name has the same length, the file is called after the BPEL file that it is tight too. And so to get the base name, the part without the "_sensor.xml" postfix, we need to determine the length of the filename. A script that determines that can easily be extracted from the script above:
  <scriptdef name="getlength" language="javascript">
    <attribute name="text"/>
    <attribute name="property"/>
       var text = attributes.get("text");
       var length = text.length();
       project.setProperty(attributes.get("property"), length);

Perfect! Using this I could create the logic in ANT to determine the sensorAction file name. However, I thought that it would be easier to determine the filename in Javascript all the way. Using the strength of the proper language at hand:
  <!-- Script to get the sensorAction filename based on the sensor filename. 
  1. Cut the extension "_sensor.xml" from the filename.
  2. Add "_sensorAction.xml" to the base filename.
  <scriptdef name="getsensoractionfilename" language="javascript">
    <attribute name="sensorfilename"/>
    <attribute name="property"/>
       var sensorFilename = attributes.get("sensorfilename");
       var sensorFilenameLength = sensorFilename.length();
       var postfixLength = "_sensor.xml".length();
       var sensorFilenameBaseLength=sensorFilenameLength-postfixLength;
       var sensorActionFilename=sensorFilename.substring(0, sensorFilenameBaseLength)+"_sensorAction.xml";
       project.setProperty(attributes.get("property"), sensorActionFilename);
And then I can get the sensorAction filename as follows:
    <getsensoractionfilename sensorfilename="${}" property=""/>
    <echo message="Sensor Action file: ${}"></echo>

Superb! I found ANT a powerfull language/tool already. But with a few simple JavaScript snippets you can extend it easily.
Notice by the way also the use of xslt in the Scan JCA adapters files article. You can read xml files as properties, but to do that conveniently you need to transform a file like the sensors.xml in a way that you can easily reference the properties following the element-hierarchy. This is also explained in the Scan JCA adapters files article.
I'll go further with my sensors scan script. Maybe I'll write about it when done.

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