GGTS: Clean up Grails 2.0 output

Ted VinkeMarch 3rd, 2015Last Updated: February 27th, 2015

0 139 1 minute read

Have you ever had in Groovy/Grails Tool Suite (GGTS) that console output, by a running Grails application, which is exactly the same as the previous output, just isn’t displayed?

This can often be seen with println statements for debug-purposes e.g. in a Controller, which you think should output some line to the console every time, but simply doesn’t.

class TestController {
	def index() { 
		println "index called"
	}
}

When http://localhost:8080/test/test/index is invoked repeatedly in the browser, you just keep seeing only the first occurence.

....index called

When the same message repeatedly is sent to the console a certain convenience feature of GGTS swallows some output – if it looks the same. It has to do with the – since Grails 2.0 introduced – ANSI codes to make some output to the console coloured or re-appear on the same line.

Kris de Volder gives a nice example in JIRA issue STS-3499 about how multiple lines such as

Resolving Dependencies.
Resolving Dependencies..
Resolving Dependencies...
Resolving Dependencies....

are supposed to ‘rewrite over themselves’ on ANSI-supported consoles, so you’d only see

Resolving Dependencies...<increasing periods>

on the same line.

Output in the GGTS non-ANSI-enabled console is stripped from these codes – which would result in additional output which some people find unpleasant. So GGTS uses a workaround – which is enabled by default – and strips the beginning of the output which matches previous output and only print the remainder.

So if you were wondering why

class BootStrap {
	def init = { servletContext ->
		['A', 'B', 'B'].each { println it }
	}
}

would only print

|Running Grails application
A
B
|Server running. Browse to http://localhost:8080/test

instead of

|Running Grails application
A
B
B
|Server running. Browse to http://localhost:8080/test

you know now this is not a bug :-)

You have to disable the option ‘Clean Grails 2.0 output‘ in the GGTS preferences under Groovy > Grails > Grails Launch to prevent this swallowing-behaviour.