CODEWITHSUNDEEP
javaooparchitecturesoftware-design
Tristan Sparks
Tristan Sparks

Reputation: 21

How to structure complex objects with related fields which need to be initialized at the same time

I am implementing an API and I keep running into this issue, I think there is something wrong with my core design but I'm not sure what and I'm feeling overwhelmed by design principles.

Basically I'll have an object with a bunch of related fields. It is non-trivial to populate the fields with the proper info and relies on one or more external API calls using a client I pass in to the constructor, these API calls also provide information related to more than one field, thus it is desirable to populate many fields at the same time. I want to keep the constructor simple/fast and keep my object testable so I don't put any logic there, just assignments. However, what I end up doing is creating a single method to populate all the fields and calling this in all of my getters after a null check, i.e. lazily populating the object fields.

I think that this is bad because it violates the "fail-fast" principle, especially because I am using a client to call an external service, which may fail if, say, the client credentials are invalid. However, I am having trouble restructuring my code.

I've thought about extracting the client logic into a service/connector, ClothingConnector for example, however I'm not sure this would solve my problem as I still wouldn't want to call this in the constructor, and it would still be beneficial to populate many fields at once.

class Person {
    ClientToGetClothing clothingClient;

    Pants pants;
    Shirt shirt;
    Fabric shirtFabric;
    Fabric pantsFabric;

    public Person(ClientToGetClothing clothingClient) {
         this.clothingClient = clothingClient;
    }

    private void populateClothing() {
         PantsResponse pantsInfo = clothingClient.retrievePantsInfo();
         this.pants = pantsInfo.getPants();

         ShirtResponse shirtInfo = clothingClient.retrieveShirtInfo();
         this.shirt = pantsInfo.getShirt();

         // do some more things with my pants + shirt and assign results to more fields, calculate the fabric in this example

    }

    public Shirt getShirt() {
        if (shirt == null) {
            populateClothing;
        }
        return this.shirt;
    }
    // ...
}

Upvotes: 2

Views: 115

Answers (1)

Arpan Kanthal
Arpan Kanthal

Reputation: 503

Firstly, I would decouple the ClothingClient from the Person object. Have a factory do the attribute population and then return the person class. https://en.wikipedia.org/wiki/Factory_method_pattern#Java

Upvotes: 1

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