JPA Specification, using like againt List<String>

Question

I'm having a problem to use like on List field.

Entity class:

@Entity
public class ToSearch{

    @Convert(converter = CollectionConverter.class)
    private List<String> myList;

    //... OTHER FIELDS ...

}

The converter class:

public class CollectionConverter implements AttributeConverter<List<Object>, String> {

    private ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public String convertToDatabaseColumn(List<Object> object) {
        try {
            return objectMapper.writeValueAsString(object);
        } catch (JsonProcessingException e) {
            return "";
        }
    }

    @Override
    public List<Object> convertToEntityAttribute(String data) {
        try {
            return objectMapper.readValue(data, new TypeReference<List<Object>>() {
            });
        } catch (Exception e) {
            return null;
        }
    }
}

And a simple specification:

predicates.add(criteriaBuilder.like(criteriaBuilder.lower(root.get("myList")), "%"+ term + "%")));

My goal is simple, just search a term string, treating this as a simple String.

In fact, in database, myList is a String and like search works fine.

But... When I execute this...

Parameter value [%BLA%] did not match expected type [java.util.List (n/a)]

Any ideas?

Answer 1

Finally, as the error says, I need to change the field I'm searching for to a compatible kind of data.

criteriaBuilder.like(criteriaBuilder.lower(root.get("myList").as(String.class)), "%" + term + "%")));

Doing this, JPA treats myList as a string, there is no incompatible types any more.