The Amber Query API resembles the JDBC PreparedStatement with
enhanced SQL and direct support for objects.
tutorialquery
resin-web.xml configuration
persistence.xml configuration
The student bean
The house bean
The course servlet
@Entity
public class House {
@Id@Column(name="id")
public long getId()
@Basic
public String getName()
@OneToMany(targetEntity=Student.class,
mappedBy="house")
public Collection getStudentList()
}
@Entity
public class Student {
@Id@Column(name="id")
public long getId()
@Basic
public String getName()
@ManyToOne@JoinColumn(name="house")
public House getHouse()
}
private void doService(PrintWriter out)
throws java.io.IOException
{
Query allHouse = _entityManager.createQuery("SELECT o FROM House o");
String sql = ("SELECT s" +
" FROM House h, IN(h.studentList) s" +
" WHERE h.id=?1 AND s.gender='M'");
Query boysInHouse = _entityManager.createQuery(sql);
List houses = allHouse.getResultList();
for (int i = 0; i < houses.size(); i++) {
House house = (House) houses.get(i);
out.println("<H3>Boys living in " + house.getName() + ":</H3>");
boysInHouse.setParameter(1, new Long(house.getId()));
List boys = boysInHouse.getResultList();
if (boys.size() == 0)
out.println("No boys are living in " + house.getName());
for (int j = 0; j < boys.size(); j++) {
Student boy = (Student) boys.get(j);
out.println(boy.getName() + "<br>");
}
}
}
}