HQL查询语言的使用介绍

HQL查询依赖于Query类，每个Query实例对应一个查询对象，使用HQL查询按如下步骤进行：

1.获取Hibernate Session对象
2.编写HQL语句
3.以HQL语句作为参数，调用Session的createQuery方法创建查询对象
4.如果HQL语句包含参数，则调用Query的setXxx方法为参数赋值
5.调用Query独享的list()或uniqueResult()方法返回查询结果列表

简单的例子：

    private static final SessionFactory sessionFactory;

    static {
        sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
    }

    public static Session getOpenSession() {
        return sessionFactory.openSession();
    }

    public static Session getCurrentSession() {
        return sessionFactory.getCurrentSession();
    }
}
@Entity
public class Employee {

    private Integer id;
    private String name;
    private Integer age;

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Basic
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Basic
    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String toString() {
        return "id:" + id + "   " + "name:" + name +  "   " + "age:" + age;
    }
}
@SuppressWarnings("all")
public class HQLDemo {

    @Test
    public void testHQL() {
        Session session = HibernateUtil.getOpenSession();
        List<Employee> employeeList = session.createQuery("from Employee as e").list();
        for(Employee e : employeeList)
            System.out.println(e);
    }

    @Test
    public void testHQLHasParameter() {
        Session session = HibernateUtil.getOpenSession();
        List<Employee> employeeList = session.createQuery("from Employee as e where e.name = :personName").setString("personName", "xujianguo").list();
        for(Employee e : employeeList)
            System.out.println(e);
    }
}