Question

Here is my class:

public class TrainLate {

private int id;
private Date startDate;
private Date endDate;
private Set<TrainSchedule> ts=new HashSet<TrainSchedule>(); 
public TrainLate(){}
public TrainLate(int id, Date startDate, Date endDate) {
    super();
    this.id = id;
    this.startDate = startDate;
    this.endDate = endDate;
}

    // setters and getters...
}

The type Date is java.sql.Date

In another class I use HQL:

String hql="SELECT new TrainLate(id,startDate,endDate) FROM TrainLate "+                "WHERE id="+String.valueOf(index);

where index is an int parameter.

Here is the “TrainLate.hbm.xml”:

<class name="classes.TrainLate">
    <id name="id">
        <generator class="native"/>
    </id>
    <property name="startDate"/>
    <property name="endDate"/>
    <set name="ts"  lazy="false" cascade="all-delete-orphan" inverse="true">
           <key column="trainLateID" />
           <one-to-many class="classes.TrainSchedule" />
          </set>  
</class>

Here is the exception:

Unable to locate appropriate constructor on class [classes.TrainLate] [SELECT new TrainLate(id,startDate,endDate) FROM classes.TrainLate WHERE id=0]

Where “classes” is the package name.

Answer 1

First: Hibernate requires your entities to have a default no argument constructor.

Second: Your hql should be: "from TrainLate t where t.id = :id".

String hql = "from TrainLate t where t.id = :id";
List<TrainLate> result = (List<TrainLate>) session.createQuery(hql).setParameter("id", 1).list();

Or even better. When you know the id of the entity you don’t need to search with hql:

TrainLate t = session.get(TrainLate.class, 1L); // I assume your id is a Long

This one returns null if the entity is not found.

or

TrainLate t = session.load(TrainLate.class, 1L); // I assume your id is a Long

This one throws an ObjectNotFoundException if the entity is not found.