How to access nested JSON in Apex?

Question

I'm new to Apex and I would appreciate some help with the following:

The code below returns the entire list from input:

public static string input ='[{"item1": 1,"item2": "2","item3": [{"child1": "11","child2": "22","child3": 33}]},{"item1": "aa","item2": "bb","item3": [{"child1": "22","child2": "33","child3": 12}]}]';

List<Object> jsonParsed = (List<Object>) JSON.deserializeUntyped(input);
System.debug(jsonParsed);

and I want to get the child of "item3", so that I can read:

"item1": "1" "child1": "11" "child2": "22" "child3": 33

I have tried the code below without success, and I get item1 but null for child 1,2 and 3.

for(Object jsonParsed : jsonParsed){
        Map<String,Object> ind = (Map<String,Object> )jsonParsed;
        System.debug('item1 = '+ ind.get('item1'));        
        System.debug('child1 = '+ ind.get('item3.child1[0]'));
        System.debug('child2 = '+ ind.get('item3.child2[1]'));
        System.debug('child3 = '+ ind.get('item3.child3[2]'));
    }

thanks."without success" meaning that i was not able to get the expected results — Jav Hens
– Jav Hens, Commented Mar 13, 2020 at 19:45
I just modified my post to give more details about what I got instead. — Jav Hens
– Jav Hens, Commented Mar 13, 2020 at 22:45

David Reed · Accepted Answer · 2020-03-14 16:55:40Z

1

Apex does not support relationship paths or expressions in the get() method like this:

    System.debug('child1 = '+ ind.get('item3.child1[0]'));

That will simply return null.

You must access each level of structure in the JSON in sequence, and if you are using deserializeUntyped() you must also cast data structures at each level (because get() returns the generic type Object):

    Map<String, Object> item3 = (Map<String, Object>)ind.get('item3');
    List<Object> child1 = (Map<String, Object>)item3.get('child1');
    Object child1Item = child1[0];

    System.debug('child1 = ' + child1Item);

It's generally much easier, where possible, to define a strongly-typed Apex class representing your JSON and deserialize into that. Your JSON is generic enough here that I don't see how to do that; you would need to look at the actual data types and keys and consider using a tool like JSON2Apex.

answered Mar 14, 2020 at 16:55

David Reed

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2 Comments

Jav Hens Over a year ago

Thank you David but I tried the sugested code and I get the followin error code: Illegal assignment from Map<String,Object> to List<Object> Would you mind to ellabotrate?

David Reed Over a year ago

@Jav I was looking at your code and didn't notice that it doesn't currently match your JSON. Please take this code as a general suggestion or pattern. You actually have several nested lists in your JSON that you need to index through as additional layers of structure. I really do recommend if at all possible going the route of typed deserialization.

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