Case insensitive isMember in loop - JPA criteria api - jpa

Question

I created the following predicate that matches a given set of string e.g. "a,b,c" against an column containing an #ElementCollection Set<String>.
I want all entries that contain "a" or "b" or "c". E.g. all these entries/set match:
a //because of a
b,d //because of b
c,f,g //because of c
I have a predicate that is working - i only need to make it case insensitive (don't want to change the data base):
private Predicate matchStringSet(Set<String> set, SetAttribute<DeliveryModeEntity, String> attribute,
CriteriaBuilder criteriaBuilder, Root<DeliveryModeEntity> deliveryMode) {
List<Predicate> matchEach = new ArrayList<>();
for (String string : set) {
matchEach.add(criteriaBuilder.isMember(string.toLowerCase(), deliveryMode.get(attribute)));
}
return criteriaBuilder.or(matchEach.toArray(new Predicate[] {}));
}
How to make deliveryMode.get(attribute) use lower case or how to make this case insensitive.
I tried to use a join as mentioned here: https://stackoverflow.com/a/10225074/447426
but this is not working within a for loop - it will create a join per string in set.

Answer 1

I have a similar entity, Widget, having tags:
#ElementCollection
#Column(name = "tag")
private List<String> tags = new ArrayList<>();
With what you have, to find all widgets having given tags use:
private Predicate matchTags(List<String> tags, Root<Widget> root, CriteriaBuilder cb) {
List<Predicate> predicates = new ArrayList<>();
for (String tag : tags) {
predicates.add(cb.isMember(tag, root.get(Widget_.tags)));
}
return PredicateReducer.OR.reduce(cb, predicates); // cb.or(predicates.toArray(new Predicate[0]));
}
To find all Widgets having given tags in a case-insensitive way, first join the tags and then perform a like search:
private Predicate matchTagsCaseInsensitive(List<String> tags, Root<Widget> root, CriteriaBuilder cb) {
List<Predicate> predicates = new ArrayList<>();
Join<Widget, String> joinedTag = root.join(Widget_.tags);
for (String tag : tags) {
predicates.add(cb.like(cb.lower(joinedTag), tag.toLowerCase()));
}
return PredicateReducer.OR.reduce(cb, predicates); // cb.or(predicates.toArray(new Predicate[0]));
}
Edit: Adding PredicateReducer
I find myself AND-ing or OR-ing predicates often, so wrapped those operations into an enum:
public enum PredicateReducer {
AND {
#Override
public Predicate reduce(CriteriaBuilder cb, List<Predicate> predicates) {
return cb.and(predicates.toArray(new Predicate[0]));
}
},
OR {
#Override
public Predicate reduce(CriteriaBuilder cb, List<Predicate> predicates) {
return cb.or(predicates.toArray(new Predicate[0]));
}
};
public abstract Predicate reduce(CriteriaBuilder cb, List<Predicate> predicates);
public Predicate reduce(CriteriaBuilder cb, Predicate... predicates) {
return reduce(cb, Arrays.asList(predicates));
}
}