Execute SQL-LIKE with List attribute - sql

Question

I have this method on my Dao class:
public List<E> search(String key, Object value) {
EntityManager entityManager = getEntityManager();
entityManager.getTransaction().begin();
List result = entityManager.createQuery("SELECT a FROM "+clazz.getSimpleName()+" a WHERE a."+key+" LIKE '"+value+"%'").getResultList();
entityManager.getTransaction().commit();
entityManager.close();
return result;
}
the sql works fine when the attribute is #Column or a #OneToOne`, but when it's something like that:
#OneToMany(fetch = FetchType.EAGER, cascade=CascadeType.ALL)
#OrderColumn
private List<Titulo> nome;
where the class Titulo has this attributes:
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Integer id;
#Column
private String idioma;
#Column(length=32)
private String conteudo;
causes this error:
message: left and right hand sides of a binary logic operator were incompatible [java.util.List(org.loja.model.categoria.Categoria.nome) : string]; nested exception is org.hibernate.TypeMismatchException: left and right hand sides of a binary logic operator were incompatible [java.util.List(org.loja.model.categoria.Categoria.nome) : string]
How I can change the method to make work for both types of attributes?

Answer 1

I manage to solve this issue with the approach below, using java reflection to detect the type of the field trying to be queried, and using a proper sql command. Don't know how efficient this can be; if anyone have a better solution to this, feel free to add another answer with it.
public List<E> search(String key, Object value) throws NoSuchFieldException {
EntityManager entityManager = getEntityManager();
entityManager.getTransaction().begin();
List result;
Field field = clazz.getDeclaredField(key);
ParameterizedType listType = (ParameterizedType) field.getGenericType();
Class<?> classElement = (Class<?>) listType.getActualTypeArguments()[0];
String nome = classElement.getSimpleName();
Field field2[] = classElement.getDeclaredFields();
String attr = field2[field2.length - 1].getName();
if(field != null) {
if(field2 != null) {
result = entityManager.createQuery("SELECT a FROM "+clazz.getSimpleName()+" a, "+nome+" b WHERE b."+attr+" LIKE '"+value+"%'").getResultList();
} else {
result = entityManager.createQuery("SELECT a FROM "+clazz.getSimpleName()+" a, "+nome+" b WHERE b LIKE '"+value+"%'").getResultList();
}
} else {
result = entityManager.createQuery("SELECT a FROM "+clazz.getSimpleName()+" a WHERE a."+key+" LIKE '"+value+"%'").getResultList();
}
entityManager.getTransaction().commit();
entityManager.close();
return result;
}
UPDATE
I got one issue with the code above: in the first query (of the three in the if/else), it's always returned all the elements of the table, almost if the LIKE was being ignored.