Hibernate Restrictions.isEmpty() is not working

Question

I am trying to learn hibernate. Right now I am studying criteria query. Here I have got trouble with Restrictions.isEmpty(). Can anyone please help me on this please ? Here are my attempts below ::

In my method >>>

Criteria cr = session.createCriteria(EmployeeCriteria.class);
        cr.add(Restrictions.isEmpty("salary"));
        List results = cr.list();           
        for (Iterator iterator = results.iterator(); iterator.hasNext();) {
            EmployeeCriteria employee = (EmployeeCriteria) iterator.next();
            System.out.println("#####  - Employee #" + employee.getId() + " - #####");
            System.out.println("===============================");
            System.out.print("Employee ID: " + employee.getId());
            System.out.print(" ||  First Name: " + employee.getFirstName());
            System.out.print(" ||  Last Name: " + employee.getLastName());
            System.out.println(" ||  Salary: " + employee.getSalary());
        }

And it's giving this error >>>

org.hibernate.MappingException: Property path [criteria.EmployeeCriteria.salary] does not reference a collection
at org.hibernate.criterion.AbstractEmptinessExpression.getQueryableCollection(AbstractEmptinessExpression.java:84)
at org.hibernate.criterion.AbstractEmptinessExpression.toSqlString(AbstractEmptinessExpression.java:63)
at org.hibernate.loader.criteria.CriteriaQueryTranslator.getWhereCondition(CriteriaQueryTranslator.java:380)
at org.hibernate.loader.criteria.CriteriaJoinWalker.<init>(CriteriaJoinWalker.java:113)
at org.hibernate.loader.criteria.CriteriaJoinWalker.<init>(CriteriaJoinWalker.java:82)
at org.hibernate.loader.criteria.CriteriaLoader.<init>(CriteriaLoader.java:92)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1697)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)

MY EmployeeCriteria POjo

    import javax.persistence.*;

@Entity
@Table(name = "employee_criteria")
public class EmployeeCriteria {
   @Id @GeneratedValue
   @Column(name = "id")
   private int id;

   @Column(name = "first_name")
   private String firstName;

   @Column(name = "last_name")
   private String lastName;

   @Column(name = "salary")
   private int salary;  

   public EmployeeCriteria() {}
   public int getId() {
      return id;
   }
   public void setId( int id ) {
      this.id = id;
   }
   public String getFirstName() {
      return firstName;
   }
   public void setFirstName( String first_name ) {
      this.firstName = first_name;
   }
   public String getLastName() {
      return lastName;
   }
   public void setLastName( String last_name ) {
      this.lastName = last_name;
   }
   public int getSalary() {
      return salary;
   }
   public void setSalary( int salary ) {
      this.salary = salary;
   }
}

Answer 1

isEmpty() is a method for lists. You are checking salary, which probably isn't a list, but more like a float or something. Use something like criteria.add(Restrictions.ne("salary","")); or criteria.add(Restrictions.isNotNull("salary")); instead.