Removing a Given Key from a Groovy Map

Question

I'm sure this is a very simple question, but I'm very new to Groovy and it's something I've been struggling with for awhile now. I have an HttpServletRequest and I need to do something with it's parameters. However, I want to exclude exactly 1 parameter.

Previously, I was using

req.getParameterMap

However, to remove the one value, I'm trying something along the lines of

def reqParams = req.getParameterMap?.remove('blah');

I know that the above does not quite work, but that's the psuedo-code for what I'm trying to achieve. I really need the new Map and the original req.getParameterMap() Objects to look exactly the same except for the one missing key. What's the best way to achieve this? Thanks!

Solution 1

req.getParameterMap returns an immutable map which cannot be modified. You need to create a new map, putAll from the parameter map and remove the required key you do not want.

def reqParams = [:] << req.getParameterMap()
reqParams.remove('blah')

You have your new map as reqParams (without the undesired key value pair) and the original parameter map.

Solution 2

You can use findAll function, somethig like:

def map = req.getParameterMap().findAll {it.key != 'blah'}

Comments

[Mr. Cat]

Do you use grails or just add groovy support to your java app?

[JToland]

Just being used within a java app.

[Mark Florence]

I like this answer much better as it is easily generalized (for example) to remove all keys beginning with blah, as in: def map = req.getParameterMap().findAll {!it.key.startsWith('blah')}

[Renato]

Nice, but it's a real pitty they didn't make map - key work also :D (notice that map - [key: 'value'] works but you need to know the value, not just the key)