Merge maps with recursive nested maps in Groovy

Question

I would like to know if someone have an easy way to merge 2 deep nested maps together ?

For instance, I would like to get :

[
    "a" : "1",
    "animals" : ["cat" : "blue"]
] + [
    "b" : 2,
    "animals" : ["dog" : "red"]
] == [
    "a" : 1,
    "b" : 2,
    "animals" : [
        "cat" : "blue",
        "dog" : "red"]
]

There is someone having easy solution ?

Answer 1

You can write one for Map using recursion:

Map.metaClass.addNested = { Map rhs ->
    def lhs = delegate
    rhs.each { k, v -> lhs[k] = lhs[k] in Map ? lhs[k].addNested(v) : v }   
    lhs
}

def map1 = [
    "a" : "1",
    "animals" : ["cat" : "blue"]
]

def map2 = [
    "b" : 2,
    "animals" : ["dog" : "red"]
]

assert map1.addNested( map2 ) == [
    a: '1', 
    animals: [cat: 'blue', dog: 'red'], 
    b: 2
]