How to update only Non Null Json fields of a Object in an Existing Json Object in Android

Question

Suppose, we have a User JSON response:

{
    "name": "Jack",
    "age": 28,
    "address": "Some address",
    "occupation": "Employee",
    "gender":"male"
}

With some network calls, we got another JSON response:

{ "age":"27", "address":"Some new address" }

Now, the requirement is to update the existing object with the updated fields. For e.g:

{
    "name": "Jack",
    "age":"27",
    "address":"Some new address",
    "occupation": "Employee",
    "gender":"male"
}

Notice that age and address was changed. This can be done by making null checks for small user object but doesn't look smart enough for some object like Product that will have more than 100 fields.

Looking for an efficient way to do it in Java/Kotlin.

Possible duplicate of [How to join two JavaScript Objects, without using JQUERY](https://stackoverflow.com/questions/21450060/how-to-join-two-javascript-objects-without-using-jquery) — Ctznkane525, Apr 10 '19 at 19:56
I am not looking for solution in JavaScript but in Java or kotlin — codepeaker, Apr 10 '19 at 20:10
@codepeaker Start by breaking this into several smaller pieces. First you need to parse the JSON response. Then you need to determine how you represent the object in Kotlin. Then you need to update the individual fields in that representation. — Code-Apprentice, Apr 10 '19 at 20:11
@Alexander That will be one of the way, but Incorporating DB in an app won't be a good idea for the sake of solution — codepeaker, Apr 10 '19 at 20:13
Traversing through individual fields won't be maintainable in the long run — codepeaker, Apr 10 '19 at 20:15
Possible duplicate of [Helper in order to copy non null properties from object to another ? (Java)](https://stackoverflow.com/questions/1301697/helper-in-order-to-copy-non-null-properties-from-object-to-another-java) — Michał Ziober, Apr 10 '19 at 20:19

score 1 · Answer 1 · answered Apr 10 '19 at 20:34

You can use a HashMap for it, let the value name be a key, and the value will be a value ))) :

HashMap<String, String> hashMap = new HashMap<String, String>(); 


    hashMap.put("name", "Jack"); 
    hashMap.put( "age", "27");

Now, if you need to update values, just add it with the same key:

 hashMap.put( "age", "67");

Now you just need to iterate through your hashMap and get all values back, it could be like this:

 Iterator it = hashMap.entrySet().iterator();
 while (it.hasNext()) {
    Map.Entry pair = (Map.Entry)it.next();
    System.out.println(pair.getKey() + " = " + pair.getValue());
    it.remove();
 }

And no dataBase, as you can see )))

score 1 · Answer 2 · answered Apr 10 '19 at 20:37

A JSONObject is essentially just a map of keys/values. Assuming you only care about one level deep, a trivial approach here would be to just map the key/values from the second object (where the values are not null) to the current object.

This could be defined as an extension function on JSONObject, such as:

fun JSONObject.mergeWith(other: JSONObject): JSONObject = apply {
    other.keys()
        .asSequence()
        .associateWith(other::get)
        .filterValues { it != null }
        .forEach { (key, value) -> this.put(key, value) }
}

For example:

val firstJson = JSONObject().apply {
    put("x", 1)
    put("y", "1")
}

val secondJson = JSONObject().apply {
    put("x", 2)
    put("y", null)
}

val mergedJson = firstJson.mergeWith(secondJson) // contains x = 2, y = "1"

Plus 1 Seems fine but I have to convert JSONObject to User object which I think is a overhead. — codepeaker, Apr 12 '19 at 09:47
Alternatively I converted the class members to field array and merged both the object with null check. — codepeaker, Apr 12 '19 at 09:56

How to update only Non Null Json fields of a Object in an Existing Json Object in Android

2 Answers2