Use WHERE clause with instances in hql - hql

Question

How to select a record from a table using WHERE clause and comparing instances (patient)
public History findHistory(Patient patient) { History model=null;
Session sesion=util.HibernateUtil.getSessionFactory().getCurrentSession();
String sql="FROM History h WHERE h.patients=" + patient;
try{
sesion.beginTransaction();
model=(History) sesion.createQuery(sql).uniqueResult();
sesion.beginTransaction().commit();
}
catch(Exception e){
sesion.beginTransaction().rollback();
}
return model;
}
That throws a queryException #1562
e.queryString="FROM entidad.Historia h WHERE h.pacientes=entidad.Paciente#3ad3a221"
e.detailMessage="unexpected char: '#'"

Answer 1

The problem with your code is that concatenating patient like you do will just append patient.toString(), which in your case is the default implementation (i.e. classname#hashcode) and it is no use for Hibernate to find out which data to retrieve in the DB.
You need to bind the parameter, first:
String sql = "FROM History h WHERE h.patients = :patient";
Then
model = (History) sesion.createQuery(sql)
.setParameter("patient", patient)
.uniqueResult();
Edit:
SQLGrammarException: could not execute query can occurs for various reason. Try to run the generated query in SqlDeveloper (or any other tool) and see what your DB says. In your case, the last part and .=? cause the error. The cross join is Harming too. I suspect your mapping is incomplete and Hibernate can't find how to join History and Patient. Try to add something like this in History entity:
#ManyToOne
#JoinColumn(name = "patient")
private Patient patient;