@Entity
@Table(name = "person")
public class Person {
    @Id
    private int id;
...
    @Convert(converter = HashMapConverter.class)
    private Map<String, Object> attributes = new HashMap<>();
...
}

public class HashMapConverter implements AttributeConverter<HashMap<String, Object>, String> {

    private final ObjectMapper mapper = new ObjectMapper();

    @Override
    public String convertToDatabaseColumn(HashMap<String, Object> stringObjectHashMap) {
        try {
            return mapper.writeValueAsString(stringObjectHashMap);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public HashMap<String, Object> convertToEntityAttribute(String string) {
        try {
            return mapper.readValue(string, new TypeReference<>() {});
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}