CODEWITHSUNDEEP
java-8jacksonoption-type
Julio
Julio

Reputation: 439

Accessing internal json field with optional checking null

I have a json like this:

{
    "name": "car",
      "attributes": {
        "lon": 13,
        "lat": 15
    }
}

Sometimes some attributes can be null.

Optional<Attributes> op = Optional.ofNullable(json);

if (op.isPresent()) {
    Optional<Integer> opI = Optional.ofNullable(op.get().getLon());
   opI.ifPresent(....);
}

How can avoid using Optional in many lines, is there a safe way to reduce it. Imagine you have a json like this.

{"object1": {
    "object2": {
       "object3": {
           "object4: {

and you need to access to object4 but checking if some of the previous objects are null, with my approach using optional. It wouldn't be the best and more elegant solution.

What can I do it in an elegant way using optional and reducing the code?

Upvotes: 1

Views: 401

Answers (1)

ernest_k
ernest_k

Reputation: 45329

You just use Optional.map, which skips the code you give it when the optional is empty

Integer lon = Optional.ofNullable(json).map(Attributes::getLon).orElse(null);

You can chain any number of intermediate map() calls on successive optionals. map() will skip the call to the function you give it if the optional is empty.

So, for your other case:

var object4 = Optional.ofNullable(mainObject)
                  .map(MainObject::getObject1)
                  .map(Object1:getObject2)
                  .map(Object2:getObject3)
                  .map(Object3:getObject4)
                  .orElse(null); //set object4 to null if anything was missing

Important to keep in mind (from the linked JavaDocs):

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise return an empty Optional.

So if any getObjectN returns null, the resulting optional will be empty.

Upvotes: 1

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