I only recently encountered the Jenkinsfile format. Previously I had used the clunky Jenkins UI or the cleaner Circle CI options.
Some of my colleagues had described it as using a special Groovy declarative syntax. It is in fact simply Groovy code using some neat tricks.
Groovy allows a closure (what other languages may call a lambda) to be used as a function parameter:
def block(Closure closure) {
closure.call()
}
This can then be used as follows:
block( { print (‘hello’) } )
Groovy allows the closure to be moved outside the brackets as a code block:
block() {
print ‘hello’
}
Here I have started to use the groovy trick of dropping brackets. In fact you can also drop the leading brackets:
block {
print ‘hello’
}
This is beginning to look like the pipeline or stage steps from a Jenkinsfile.
You can even add parameters:
def wrap(marker, Closure closure{
println marker
closure.call()
println marker
}
// Which can be used as:
wrap (‘name’) {
// something …
}
Jenkinsfiles are code pretending to be config, with the added benefit of being able to become code again when needed.
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