Friday, 28 February 2014

Eclipse Groovy REPL script to sync a Browser with file changes (with recursive folder search via Java's WatchService)

Since I am using Eclipse to develop using AngularJS (see Creating an Eclipse UI to run AngularJS e2e tests using Karma), I needed a way to refresh the browser window every-time I made changes to any AngularJS related file (note that due to the nature of the AngularJS projects, I need the change to trigger on any change made inside the root folder and all its subfolders).

Since there didn't seem to be an easy way to do this ('auto browser refresh on file changes') in  Eclipse, I used the Eclipse Grovy REPL Scripting Environment to develop a script/macro that:
  • Based on a title of an opened eclipse editor file:
  • ... find the full path of that file, and:
  • ... create a Java WatchService that monitors the file's folder and subfolders, and:
  • ... when a StandardWatchEventKinds.ENTRY_MODIFY is received :
    • Create/Open a new Eclipse view with a browser (called Synced Browser), and:
    • ...refresh the index page 
For reference here is the groovy code for this script (gist here):

Originally I had tried to use Eclipse file change events (like on this SO thread), but that didn't work as well as the WatchService.

A next step is to create a mini UI to allow the configuration of the target files (maybe as a view added to the next version of the Groovy REPL Eclipse plugin)

Seeing it in action

Here is how to test this script:

1) create a Web project with an Html file on it:

2) run the Groovy code in the REPL window (note that the image below is using a different root file and the version of script is an older one (which didn't contain the recursive folder monitoring)):

... on execution you will see a new view (called Synced WebBrowser) show up in your current Eclipse instance.

3) make some changes on the Html file

4) and note that the Synced WebBrowser view will be refreshed automatically (it takes about 500ms to 1s for the change to be picked up (see this SO answer for why I had to use the SensitivityWatchEventModifier.HIGH setting on the WatchService))

5) if you open the TeamMentor Console, you will also see a number of log messages that help to see what is going on:

6) here is another example where I added a new Bootstrap css div:

7) which was immediately (~500ms) shown on save

8) note that the the log message shows the events being triggered and the resetting of the WatcherService:

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