04Hibernate query

• Query object query
• Criteria object query
• SQLQuery object query

1. Query object

• Using the query object, you don't need to write SQL statements, but you need some hql statements

1. hql: hibernate query language, hibernate provides query language, hql statement is very similar to SQL statement;
2. Difference between hql and SQL statement
   • Manipulate tables and fields with SQL
   • Manipulate entity classes and properties using hql

• query all using hql　
  • from entity class name
• Use of the Query object

1. Create a Query object;
2. Call the method in the Query object to query the result
   

    1     public void testQuery() {
    2          SessionFactory sessionFactory = null;
    3          Session session = null;
    4          Transaction tx = null;
    5          try {
    6              sessionFactory = HibernateUtils.getSessionFactory();
    7              session =HibernateUtils.getCurrentSession();
    8              
    9              tx = session.beginTransaction();
   10              
   11              //1、创建query对象
   12              Query query = session.createQuery("from User");
   13              //2.得到查询结果 
   14              List<User> list = query.list();
   15              for (User user : list) {
   16                 System.out.println(user);
   17             }
   18              tx.commit();
   19              
   20          }catch(Exception exception) {
   21              exception.printStackTrace();
   22              tx.rollback();
   23          }finally {
   24              
   25          }
   26     }

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