标签：
HQL：Hibernate Query Language
HQL有几个特点：
package test.hibernate.hbmHQL;
import java.util.HashSet;
import java.util.Set;
public class Department {
private Integer id;
private String name;
private Set<Employee> employees = new HashSet<Employee>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Employee> getEmployees() {
return employees;
}
public void setEmployees(Set<Employee> employees) {
this.employees = employees;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return "[employee:id=" + id + ",name=" + name + "]";
}
}
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="test.hibernate.hbmHQL">
<class name="Employee" table="employee_hql">
<id name="id" type="integer" column="id">
<generator class="native" />
</id>
<property name="name" />
<many-to-one name="department" class="Department" column="departmentId"></many-to-one>
</class>
<!-- <query name="queryByIdRange"> FROM Employee e WHERE e.id BETWEEN ?
AND ? </query> -->
<!-- <query name="queryByIdRange"> FROM Employee e WHERE e.id BETWEEN :idMin
AND :idMax </query> -->
<query name="queryByIdRange">
<!--这里<小于号会被看成特殊字符而报错，用<![CDATA[...]]>包起来表示没有特殊字符 -->
<![CDATA[FROM Employee e WHERE e.id >= :idMin AND e.id <= :idMax]]>
</query>
</hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="test.hibernate.hbmHQL">
<class name="Department" table="department_hql">
<id name="id" type="integer" column="id">
<generator class="native" />
</id>
<property name="name" />
<set name="employees" cascade="all">
<key column="departmentId"></key>
<one-to-many class="Employee" />
</set>
</class>
</hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="test.hibernate.hbmHQL">
<class name="Employee" table="employee_hql">
<id name="id" type="integer" column="id">
<generator class="native" />
</id>
<property name="name" />
<many-to-one name="department" class="Department" column="departmentId"></many-to-one>
</class>
<!-- <query name="queryByIdRange"> FROM Employee e WHERE e.id BETWEEN ?
AND ? </query> -->
<!-- <query name="queryByIdRange"> FROM Employee e WHERE e.id BETWEEN :idMin
AND :idMax </query> -->
<query name="queryByIdRange">
<!--这里<小于号会被看成特殊字符而报错，用<![CDATA[...]]>包起来表示没有特殊字符 -->
<![CDATA[FROM Employee e WHERE e.id >= :idMin AND e.id <= :idMax]]>
</query>
</hibernate-mapping>
package test.hibernate.hbmHQL;
import java.util.Arrays;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.junit.Test;
public class App {
private static SessionFactory sessionFactory = new Configuration()//
.configure()//
.addClass(Department.class)// 添加Hibernate实体类（加载对应的映射文件）
.addClass(Employee.class)//
.buildSessionFactory();
@Test
public void testSave() throws Exception {
Session session = sessionFactory.openSession();
session.beginTransaction();
// --------------------------------------------
// 构建对象
for (int i = 1; i <= 10; i++) {
Department department = new Department();
department.setName("部门_" + i);
session.save(department);
}
for (int i = 1; i <= 20; i++) {
Employee employee = new Employee();
employee.setName("员工_" + i);
employee.setDepartment(null);
session.save(employee);
}
// --------------------------------------------
session.getTransaction().commit();
session.close();
}
// 获取
@Test
public void testHQL() throws Exception {
Session session = sessionFactory.openSession();
session.beginTransaction();
// ===========================================
// 获取数据
String hql = null;
// hql = "FROM Employee";//HQL中查询select可以省略，但不能用select *
// hql = "FROM Employee AS e";
// hql = "FROM Employee e";//使用别名，as关键字可以省略
// hql = "FROM Employee e WHERE e.id < 30 AND e.id > 25";
// hql = "FROM Employee e WHERE e.id < 30 ORDER BY e.id DESC";
// 有多个排序条件，先按前面的排
// hql =
// "FROM Employee e WHERE e.id < 30 ORDER BY e.id DESC,e.name ASC";
// hql = "select e.name FROM Employee e";
// hql = "select e FROM Employee e";//相当与"FROM Employee e"
// hql = "select e.id,e.name FROM Employee e";//返回一个Object数组
// hql = "select new Employee(e.id,e.name) FROM Employee e";
// // 返回对象数组,要求类中有id、name两个参数的构造函数
// // List list = session.createQuery(hql).list();
Query query = session.createQuery("FROM Employee WHERE id=200");
// // 分页
query.setFirstResult(0);// 从第一条记录开始查询，与具体的id无关
query.setMaxResults(5);
Employee employee = (Employee) query.uniqueResult();
System.out.println(employee);// 如果下标越界，查询的结果返回null
// List list = query.list();
// 方法链的形式
// List list = session.createQuery(//
// "select e.id,e.name FROM Employee e")//
// .setFirstResult(0)//
// .setMaxResults(10)//
// .list();//
// for (Object obj : list) {
// if (obj.getClass().isArray()) {
// System.out.println(Arrays.toString((Object[]) obj));
// } else {
// System.out.println(obj);
// }
//
// }
// ==========================================
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL2() throws Exception {
Session session = sessionFactory.openSession();
session.beginTransaction();
// ===========================================
String hql = null;
// 聚集函数：count()、max()、min()、avg()、sum()
// hql="SELECT COUNT(*) FROM Employee";
// Long result=(Long)session.createQuery(hql).uniqueResult();
// System.out.println(result);
// hql = "SELECT MAX(id) FROM Employee";
// Number result = (Number) session.createQuery(hql).uniqueResult();
// System.out.println(result.getClass());// 返回结果类型
// System.out.println(result.intValue());
// System.out.println(result.longValue());
// 分组group by、order by、having
// hql =
// "SELECT e.name,COUNT(e.id) FROM Employee e WHERE id <= 30 GROUP BY name";
// 过滤，只显示数量大于2的组(不能用where代替，因为分组在查询之后)
// hql="SELECT e.name,COUNT(e.id) FROM Employee e WHERE id <= 30 GROUP BY name HAVING COUNT(e.id) > 2";
// hql = "SELECT e.name,COUNT(e.id) AS c " + //
// "FROM Employee e " + //
// "WHERE id <= 30 " + //
// "GROUP BY e.name " + //
// "HAVING COUNT(e.id) = 2 " + // having子句不能使用列别名
// "ORDER BY c ASC";// order by 子句可以使用列别名
// List list = session.createQuery(hql).list();
// for (Object obj : list) {
// if (obj.getClass().isArray()) {
// System.out.println(Arrays.toString((Object[]) obj));
// } else {
// System.out.println(obj);
// }
// }
// hql =
// "SELECT e.id,e.name,d.name FROM Employee e JOIN e.department d";
// hql =
// "SELECT e.id,e.name,d.name FROM Employee e INNER JOIN e.department d";
// 左外连接，OUTER关键字可以省略
// hql =
// "SELECT e.id,e.name,d.name FROM Employee e LEFT OUTER JOIN e.department d";
// hql =
// "SELECT e.id,e.name,d.name FROM Employee e RIGHT JOIN e.department d";
// hql = "SELECT e.id,e.name,e.department.name FROM Employee e";
// List list = session.createQuery(hql).list();
// for (Object obj : list) {
// if (obj.getClass().isArray()) {
// System.out.println(Arrays.toString((Object[]) obj));
// } else {
// System.out.println(obj);
// }
// }
// 使用参数查询
// 方式一：使用?占位
// hql = "FROM Employee WHERE id=?";
// List list = session.createQuery(hql)//
// .setParameter(0, 23)//
// .list();
// hql = "FROM Employee WHERE id BETWEEN ? AND ?";
// List list = session.createQuery(hql)//
// .setParameter(0, 22)// 设置参数，第一个参数的索引为0
// .setParameter(1, 30)//
// .list();
// for (Object obj : list) {
// if (obj.getClass().isArray()) {
// System.out.println(Arrays.toString((Object[]) obj));
// } else {
// System.out.println(obj);
// }
// }
// 方式二：使用变量名
// hql = "FROM Employee e WHERE id BETWEEN :idMin AND :idMax";
// List list = session.createQuery(hql)//
// .setParameter("idMin", 22)//
// .setParameter("idMax", 30)//
// .list();
// for (Object obj : list) {
// if (obj.getClass().isArray()) {
// System.out.println(Arrays.toString((Object[]) obj));
// } else {
// System.out.println(obj);
// }
// }
// 当变量是集合时，可以使用IN，参数设置用ParameterList
// hql = "FROM Employee WHERE id IN (:ids)";
// List list = session.createQuery(hql)//
// .setParameterList("ids", new Object[] { 23, 26, 27, 28, 30 })//
// .list();
// 使用命名查询
// Query query = session.getNamedQuery("queryByIdRange");
// query.setParameter(0, 25);
// query.setParameter(1, 30);
// List list = query.list();
// Query query = session.getNamedQuery("queryByIdRange");
// query.setParameter("idMin", 25);
// query.setParameter("idMax", 30);
// List list = query.list();
/*
* update与delete,不会通知Session缓存，如要获取数据库
* 更新后的数据可以用refresh
*/
// int result = session.createQuery(//
// "UPDATE Employee e SET e.name=? WHERE id < 30")
// .setParameter(0, "张小姐")//
// .executeUpdate();
int result = session.createQuery(//
"DELETE Employee e WHERE id < ?")// delete子句里from可以省掉
.setParameter(0, 30)//
.executeUpdate();
System.out.println("result=" + result);
// for (Object obj : list) {
// if (obj.getClass().isArray()) {
// System.out.println(Arrays.toString((Object[]) obj));
// } else {
// System.out.println(obj);
// }
// }
// ===========================================
session.getTransaction().commit();
session.close();
}
}
部分截图
内连接
左外连接
右外连接
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原文地址：http://blog.csdn.net/lindonglian/article/details/46975391
