Hibernate - Criteria API

Criteria API is the preferred way of doing Queries in Hibernate.

Let us write a DAO method which uses Criteria API to get Users by their first and last names.

Update UserDAO.java, like this:

 package org.confucius;   
     
 import java.util.ArrayList;  
 import java.util.List;  
   
 import org.hibernate.Criteria;  
 import org.hibernate.Query;  
 import org.hibernate.Session;   
 import org.hibernate.Transaction;   
 import org.hibernate.criterion.Restrictions;  
     
 public class UserDAO {   
        
      // Criteria with Restrictions  
      public static List<User> getUsers (String firstName, String lastName) throws Exception{  
             List<User> users = new ArrayList<User>();  
             Session session = HibernateUtil.getSessionFactory().openSession();   
             Transaction tx = session.beginTransaction();   
         
             try {   
                  Criteria criteria = session.createCriteria(User.class);  
                    
                  criteria.add(Restrictions.eq("firstName", firstName));  
                  criteria.add(Restrictions.eq("lastName", lastName));  
   
                  users = (List<User>) criteria.list();  
                    
                  tx.commit();   
             }   
             catch (Exception e){   
                  tx.rollback();        
                  throw e;   
             }   
           
             session.close();   
          return users;  
      }  
        
        
   // HQL with parameters  
   public static List<User> getUsers (String firstName) throws Exception{   
        List<User> users = new ArrayList<User>();  
        Session session = HibernateUtil.getSessionFactory().openSession();   
        Transaction tx = session.beginTransaction();   
    
        try {   
             Query query = session.createQuery("from User where firstName = :firstName");  
             query.setParameter("firstName", firstName);  
             users = (List<User>) query.list();  
             tx.commit();   
        }   
        catch (Exception e){   
             tx.rollback();        
             throw e;   
        }   
      
        session.close();   
     return users;  
   }   
   
   // HQL with no parameters  
      public static List<User> getUsers () throws Exception{   
             List<User> users = new ArrayList<User>();  
             Session session = HibernateUtil.getSessionFactory().openSession();   
             Transaction tx = session.beginTransaction();   
    
             try {   
                  Query query = session.createQuery("from User");  
                  users = (List<User>) query.list();  
                  tx.commit();   
             }   
             catch (Exception e){   
                  tx.rollback();        
                  throw e;   
             }   
      
             session.close();   
     return users;  
   }   
        
   
   // Getting an object given its Id  
      public static User getUser (long userId) throws Exception{   
            User user = null;  
            Session session = HibernateUtil.getSessionFactory().openSession();   
            Transaction tx = session.beginTransaction();   
    
              try {   
                   user = (User) session.get(User.class, userId);  
                   tx.commit();   
              }   
              catch (Exception e){   
                   tx.rollback();        
                   throw e;   
              }   
      
              session.close();   
              return user;  
    }   
      
      
      // Persist  
      public static void persist (User user) throws Exception{   
            Session session = HibernateUtil.getSessionFactory().openSession();   
            Transaction tx = session.beginTransaction();   
     
            try {   
                 session.persist(user);   
                 tx.commit();   
                
            } catch (Exception e){   
                 tx.rollback();   
                 throw e;   
            }   
       
            session.close();   
    }   
 }   

Update your TestPersistence.java to use this new DAO method, like this:

 package org.confucius;   
   
 import java.util.Iterator;  
 import java.util.List;  
   
   
 public class TestPersistence {   
     
   public static void main(String[] args) {    
           try {  
                List<User> users = UserDAO.getUsers("Joe", "Trumpet");  
                for (Iterator<User> iter = users.iterator(); iter.hasNext();)  
                     System.out.println(iter.next());  
                  
           } catch (Exception e) {  
           e.printStackTrace();  
           }  
    }    
 }  
   

R-click on the TestPersistence.java file in your Eclipse Navigator view.
Select Run As->Java Application

You will see Joe Trumpet and details about his Cart printed to the console.