How to write complex QueryDSL queries with attribute maps

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In this article, I’ll show you how to write queries to JPA entities with attribute maps (fields marked with @ElementCollection) using QueryDSL.

Note that this is not a guide on how to structure your entity model. In most cases, you don’t even need a set of arbitrary attributes in your entity. But when you do (due to different reasons — legacy data structures, additional flexibility etc.), then the queries can get really tricky.

Suppose we have the following User entity with a map of arbitrary attributes:

@Entity
public class User implements Serializable {
    @Id
    @GeneratedValue
    private Long id;
    @ElementCollection
    @MapKeyColumn(name = "key")
    @Column(name = "value")
    private Map<String, String> attributes = new HashMap<>();
    // getters and setters skipped
}

We create an entity and persist it:

Map<String, String> attributes = new HashMap<>();
attributes.put(“name”, “Mary”);
attributes.put(“birthDate”, “18–10–1983”);
attributes.put(“personalNumber”, “42”);
User user = new User();
user.setAttributes(attributes);
entityManager.persist(user);