Hibernate学习笔记----HQL(2)

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分页查询

/** * 分页查询 */public void testPageQuery(){String hql = "FROM Employee";Query query = session.createQuery(hql);//查询第3页的内容int pageNo = 3;int pageSize = 5;List<Employee> employees = query.setFirstResult((pageNo - 1) * pageSize).setMaxResults(pageSize).list();System.out.println(employees);/** * setFirstResult(int firstResult):设定从那一个对象开始检索，参数firstResult * 表示这个对象在查询结果中的索引位置，索引位置的起始值为0，默认情况下，Query从查询结果中的第一个对象开始检索 *  * setMaxResult(int maxResult):设定一次最多检索出的对象的数目，在默认情况下Query和Criteria接口检索出查 * 询结果中的所有对象。 */}

命名化查询

//命名查询，查询语句写在hbm.xml里面，便于维护public void testNamedQuery(){Query query = session.getNamedQuery("salaryEmps");List<Employee> employees = query.setDouble("minSal", 600)   .setDouble("maxSal", 6000).list();System.out.println(employees);}

Employee.hbm.xml

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><!-- Generated 2016-7-24 23:26:24 by Hibernate Tools 3.5.0.Final --><hibernate-mapping>    <class name="cn.limbo.hibernate.entities.Employee" table="EMPLOYEES">        <id name="id" type="java.lang.Integer">            <column name="ID" />            <generator class="native" />        </id>        <property name="name" type="java.lang.String">            <column name="NAME" />        </property>        <property name="email" type="java.lang.String">            <column name="EMAIL" />        </property>        <property name="salary" type="double">            <column name="SALARY" />        </property>        <many-to-one name="department" class="cn.limbo.hibernate.entities.Department" column="DEPARTMENT_ID">        </many-to-one>    </class>    <span style="color:#ff0000;"><query name="salaryEmps"><![CDATA[From Employee e WHERE e.salary > :minSal AND e.salary < :maxSal]]></query></span></hibernate-mapping>

属性投影检索

/** * 属性投影检索 */public void testFieldQuery(){String hql = "SELECT e.email,e.salary,e.department FROM Employee e WHERE e.department = :department";Query query = session.createQuery(hql);Department department = new Department();department.setId(13);//一条记录查询出来的结果是一个Object数组List<Object[]> result = query.setEntity("department", department).list();for(Object [] objects : result){System.out.println(Arrays.asList(objects));}}@Test/** * 升级版属性投影检索，推荐使用这个方法，但是必须保证实体类一定要有一个匹配的构造器 */public void testFieldQuery2(){String hql = "SELECT new Employee(e.email,e.salary,e.department)"+ "FROM Employee e "+ "WHERE e.department = :department";Query query = session.createQuery(hql);Department department = new Department();department.setId(13);//返回的是一个Employee的集合List<Employee> result = query.setEntity("department", department).list();for(Employee emp : result){System.out.println(emp.getId() + " " + emp.getEmail() + " " + emp.getSalary() + " " + emp.getDepartment());}}

报表查询(使用Group By，max等函数)

public void testGroupBy(){String hql = "SELECT min(e.salary) , max(e.salary) "+ "FROM Employee e "+ "GROUP BY e.department "+ "HAVING min(salary) > :minSal";Query query = session.createQuery(hql);query.setDouble("minSal", 600);List<Object[]> result = query.list();for(Object[] objects : result){System.out.println(Arrays.asList(objects));}}

有一个问题

当时我测试的时候出现了stackoverflow的的错误，这是我看到的资料，挺详细的

解决方法

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