The @Builder doesnt provide a protected Builder class by default for encapsulating any build time constraint handling

[VMurthy]

Hi All

I have a small issue with the @Builder which i would like to understand if there are otherways to do this.
Currently @Builder provides a public class <ClassName>Builder. However it exposes the Default Builder class to Public too early in my opinion. Rather they could provide a level to be specified

For eg in the below class: If i dont want to provide a dfault value for runningSum and dont want a public setter; i cannot do that as the public class HasPathSumVisitorBuilder is already wide open to public and clients will use that.
If instead ; an option to set the default Builder (level=AccessLevel.PROTECTED) is given; then my own extension Builder class will be the sole point of contact and that way i can add constraints handling without exposing the default builder.

I know we could completely write the Builder class by ourselves; however the point i am noting here is; the default builder takes care of 80% of mundane code; its just that this little bit done during build() time is what i would like to add with a nice encapsulation.

Should this be raised as a feature.

thanks
Murthy
@Log4j2
@Data(staticConstructor = "of")
@Accessors(fluent = true)
@EqualsAndHashCode(callSuper = false)
@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
@Builder
public class HasPathSumVisitor implements Visitor<Integer> {
    static final Logger log = LogManager
            .getLogger(StringFormatterMessageFactory.INSTANCE);
   
    Integer targetSum;
    @Getter AtomicInteger runningSum;

    @Data(staticConstructor = "builder")
    public static class Builder extends HasPathSumVisitorBuilder {
        @Override public HasPathSumVisitor build() {
            Assert.notNull(super.targetSum,
                    "Please make sure to set the targetSum");
            //Just set runningSum to default if its null.
            if(super.runningSum==null)super.runningSum= new AtomicInteger(super.targetSum);
            Assert.state(super.runningSum.get() == super.targetSum,
                    " Running Sum cannot be different than targetSum");
            return super.build();
        }
    }
.....
}

[Reinier Zwitserloot]

Lombok doesn't generate what is already there. So, just write something like:

@Builder

public class Foo {

    private class FooBuilder {}

    private FooBuilder build() { return new FooBuilder(); }

}

this means lombok will fill your FooBuilder class (with, note, public methods, and private fields!), and it won't generate the build() method as it's already there.