read dynamic json files in java and merge them

I am struggling with json-parsing in java.
Is there a possibility to generate a representation of a random, not standardised json file in java? I tried to use gson but I didn't really understood if and how that might be possible.

So the jsonFile could look like this:

{ 
 "id":16875,
 "position":[1,2,5,7],
 "metadata":{
     "color":"blue",
     "id": "84779jh",
     "more":{ "some":"randomdata","absolutly":"noStructure"}
}

any key-value pairs are possible and the json file can be nested as much and as deep as it wants to. I need to get something like a java object out of it to be able to merge it with another json file. I just need the metadata part, the rest can be ignored.

So anybody any ideas how I could make that work? I would appreciate any helps :)

the json above merged with (this is the parent node, so we keep his id and position and just merge the metadata)

  { 
   "id":16zut,
   "position":[1,2,5,7],
   "metadata":{
     "color":"green",
     "id": "84ergfujh",
     "more":{ 
        "some":"randomdata",
        "even":"more",
        "absolutly":"noStructure"
     },
     "tags":[1,2,3,4,6,8,f7,h,j,f]
   }

would be:

  { 
   "id":16zut,
   "position":[1,2,5,7],
    "metadata":{
    "color":["blue", "green"],
    "id": ["84779jh","84ergfujh]",
    "more":{ "some":"randomdata","absolutly":"noStructure","even":"more"}
    "tags":[1,2,3,4,6,8,f7,h,j,f]
  }

Thanks in advance and have a nice day.

Solution

I got my problem solved and i am grateful thank you guys helped me with it. So let me share:

I read the 2 jsons both as a tree (i am using Jackson):

   ObjectMapper mapper = new ObjectMapper();
   JsonNode parent = mapper.readTree(new File(path)); 
   JsonNode child= mapper.readTree(new File(path));

And the merge logic isn't done yet but the basic concept is:

 Iterator<String> pIt = parent.fieldNames();
    while(pIt.hasNext())
    {
        String tempkey = pIt.next();

        if(child.path(tempkey) != null)
        {
            merged.put(tempkey,child.path(tempkey));

        }
        else{
                merged.put(tempkey,parent.path(tempkey) );
        }

    }

    try {
        String jsonString = mapper.writeValueAsString(merged);
        System.out.println(jsonString);
    } catch (JsonProcessingException e) {...}

If you think it is a dumb solution, i am open for other ideas...
But i think it might work for my needs.

greetings and thanks :)