How to query for a M:N relationship using enums with CriteriaBuilder

Question

I am curently working on a Company entity which contains a List of Area enum values. These are the areas, the company is working in. They are mapped as `@ElementCollection`. ``` @Entity public class Company { @ElementCollection @CollectionTable(name = "company2area") @Enumerated(EnumType.STRING) private List areas = new ArrayList(); ... } ``` Area is a simple enum, containing the available areas. ``` public enum Area { ASIA, AMERICA, EUROPE; } ``` I tried to query for all companies that are currently working in ASIA and AMERICA like this: ``` CriteriaQuery query = this.entityManager.getCriteriaBuilder() .createQuery(Company.class); query.where(query.from(Company.class) .get("areas") .in(Arrays.asList(Area.ASIA, Area.AMERICA))); List result = entityManager.createQuery(q) .getResultList(); ``` But all I got is an exception: ``` Caused by: java.lang.IllegalArgumentException: Parameter value [ASIA] did not match expected type [java.util.Collection] at org.hib…

Accepted Answer

It works, if I join the tables explicitly:

```
query.where(query.from(Company.class)
    .join("areas", JoinType.INNER)
    .in(Arrays.asList(Area.ASIA, Area.AMERICA)));
```

As far as I thought, both ways should result in the same query as inner join is the default, but obviously, only this one here works.

How to query for a M:N relationship using enums with CriteriaBuilder

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