JPA Store object as string identifier only

Question

Let’s say we have a User

@Entity
class User {
    String name;
    …
    ExternalSystemObject eso;
    …
}

Is there an easy way to store the ExternalSystemObject as it’s identifier only (e.g. a column eso_id: String for example) and provide a mapper to map the ID back to an object when retrieving the data?

Obviously I can define the field as String in the model but that would involve creating another object to represent the original required data model.

I thought that is a simple commonly desired behaviour but couldn’t find anything in the documentation.

SD. · Accepted Answer · 2022-03-20 18:44:49Z

1

Found a way to do that using a javax.persistence.Converter;.

@Converter
public class ExternalSystemObjectConverter implements AttributeConverter<ExternalSystemObject, String> {

    @Override public String convertToDatabaseColumn(ExternalSystemObjectConverter eso) {
        return eso.getId();
    }

    @Override public ExternalSystemObjectConverter convertToEntityAttribute(String dbData) {
        // retrieve or build eso
        return eso;
    }
}

edited Mar 20, 2022 at 18:44

answered Mar 20, 2022 at 18:36

SD.

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