Get unflatten field from json object with json path

Question

I have a json object:

{
  "context": [ 
    {"name": "John", "node": [{"id": 1, "detail": "hello"}, {"id": 2, "detail": "world"}]},
    {"name": "Andy", "node": [{"id": 3, "detail": "andy"}]},
    {"name": "Dave", "node": [{"id": 4, "detail": "dave"}]},    
  ]
}

and I want to get the list of detail of each person

  [ 
    ["hello", "world"],
    ["andy"],
    ["dave"],    
  ]

I am wondering if this is even possible? I have tried many things but the array got flatten out and that is not ideal.

Answer 1

The json you provide isn't valid (so I added a name of the array):

{
  "persons": [ 
    {"name": "John", "node": [{"id": 1, "detail": "hello"}, {"id": 2, "detail": "world"}]},
    {"name": "Andy", "node": [{"id": 3, "detail": "andy"}]},
    {"name": "Dave", "node": [{"id": 4, "detail": "dave"}]},    
  ]
}

To get all details here:

$..detail

the result of it is:

[  
    "hello",
    "world",
    "andy",
    "dave"
]

tested with http://jsonpath.curiousconcept.com/ (Jsonpath 0.8.3)

Answer 2

Okay, I'm guessing your JSON should be an array of objects and not an object containing an array. If so, then this is how you could do it;

$json = <<<EOF
[
    {"name": "John", "node": [{"id": 1, "detail": "hello"},{"id": 2, "detail": "world"}]},
    {"name": "Andy", "node": [{"id": 3, "detail": "andy"}]},
    {"name": "Dave", "node": [{"id": 4, "detail": "dave"}]}
  ]
EOF;

$map = array_map(function($object) {
    return array_map(function($detail) {
        return $detail->detail;
    }, $object->node);
}, json_decode($json));

This would then give you the values in the structure you want;

[
    ['hello', 'world'],
    ['andy'],
    ['dave']
]

Answer 3

The sample JSON has one excess comma. Assuming it has been removed, the following invocation:

jq -cf '[.context[] | [.node[] | .detail]]' input.json

produces:

[["hello","world"],["andy"],["dave"]]

http://stedolan.github.io/jq is very similar to JSONpath. See "jq for JSONpath users" .