exampleUseCase.md

Example UseCase

Given is a complex data structure:

{
  "id": "e97f6d09-ff23-41e8-94a2-f35f6a99eb9c",
  "productBundle": {
    "id": "886644d1-97b5-4698-b6ee-3ed18d352d95",
    "products": [
      {
        "id": "bdce24b8-d1ae-4fca-b993-e7d509129ada",
        "calculationParts": [
          {
            "id": "02f26e1b-e548-440d-8bfc-559d7c9fb1bd",
            "amount": -5,
            "information": {
              "key": "SPECIAL_DISCOUNT"
            }
          }, 
          {
            "id": "9f1f0368-29b8-40d7-a223-dfb672cc2077",
            "amount": 11,
            "information": {
              "key": "PRICE"
            }
          }
        ]        
      }
    ]
  }
}

If you want to get the CalculationPrice object with the id 02f26e1b-e548-440d-8bfc-559d7c9fb1bd you have to do something like:

private Optional<CalculationPart> findCalculationPart(Offer offer) {
      return Optional.ofNullable(offer)
          .map(Offer::productBundle)
          .map(ProductBundle::products)
          .orElse(List.of())
          .stream()
          .flatMap(product -> product.calculationParts().stream())
          .filter(calculationPart -> "02f26e1b-e548-440d-8bfc-559d7c9fb1bd".equals(calculationPart.id()))
          .findFirst();   
}

You have to go through the whole object structure to find the specific object. If you want to find other nodes or identify the object with another predicate you have to build a new method.

The object-finder library can help simplifying your code:

private Optional<CalculationPart> findCalculationPart(Offer offer) {
       Pair<String, String> location = Pair.of("id", "02f26e1b-e548-440d-8bfc-559d7c9fb1bd");
       return FindObjectUtils.find(offer, location, CalculationPart.class);   
}

To identify the object you have to define a io.github.mrtimeey.objectfinder.type.Pair which defines the matcher. The object-finder converts the object into a tree and traverses it. On each node the left side of the Pair will be checked if the path exists. If matched it checks if the node is equal with the right side of the Pair.

If you want to identify the object based on a nested structure you can change the Pair:

private Optional<CalculationPart> findCalculationPart(Offer offer) {
       Pair<String, String> location = Pair.of("information/key", "SPECIAL_DISCOUNT");
       return FindObjectUtils.find(offer, location, CalculationPart.class);   
}