Generate a type from a Java DTO type with many fields being null and have all getters as Optional<T>

Question

I am currently working with a Java DTO class (written by others) that has almost 300 fields where many of these end up being null. What I see in the codebase are lots of null checks and more recently I have been using Optional.ofNullable to work around this (given I come from a functional background) and find that easier to work with.

However, I would like to avoid having to remember to do that everywhere I need to access one of those fields and possibly return a different kind of object where the return type is always of Optional<T>.

There is a similar post here about the problem in Python but I would be interested in what can also be done in Java. I can of course just live with it or generate a separate class with optional getters myself but was interested if anyone has any smarter approaches or good design patterns to use for such cases.

In my case when a field is null the most common scenario is not to throw a exception but to use some fallback mechanism or default value which is why the Optional class works nicely.

Answer 1

I finally had some time to come back to this and what I ended doing in the end was to use some basic templating to generate a new class from the original one, returning Optional<T> get methods as shown below.

  public class WithOptionalGettersClass {
    private final class WithNullableGettersClass nullFields;

    public WithOptionalGettersClass(WithNullableGettersClass nullFields) {
      this.nullFields = nullFields;
    }

    public Optional<String> getName() {
      return Optional.ofNullable(this.nullFields.getName());
    }

    public Optional<String> getComment() {
      return Optional.ofNullable(this.nullFields.getComment());
    }

    public Optional<LocalDate> getDate() {
      return Optional.ofNullable(this.nullFields.getDate());
    }
    
    // With many more such getOptionalXXX methods below

If one wants to take this further then this "auto-generation" of the new class with optional getters could be integrated into the relevant build pipeline.

I hope others find this useful.