package example;
import java.io.PrintWriter;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.persistence.*;
/**
* The QueryServlet just displays the values.
*/
public class QueryServlet extends HttpServlet {
@PersistenceContext(name="example")
private EntityManager _manager;
/**
* Illustrates how to interact with the Course EJB
*/
public void init()
throws ServletException
{
Student student = null;
try {
student = _manager.find(Student.class, new Long(1));
if (student != null)
return;
} catch (Exception e) {
}
_manager.getTransaction().begin();
try {
_manager.persist(new Student("Harry Potter"));
_manager.persist(new Prefect("Ron Weasley"));
_manager.persist(new Prefect("Hermione Granger"));
} finally {
_manager.getTransaction().commit();
}
}
/**
* Illustrates how to interact with the Course EJB
*/
public void service(HttpServletRequest req, HttpServletResponse res)
throws java.io.IOException, ServletException
{
PrintWriter out = res.getWriter();
res.setContentType("text/html");
out.println("<h3>Students</h3>");
Query query = _manager.createQuery("SELECT o FROM Student o");
for (Object student : query.getResultList()) {
out.println(student + "<br>");
}
}
}