Hibernateday06 HQL（Hibernate Query Language）
HQL(hibernate query language) SQL(stander query language)
Hibernate的标准开发：O-->R--->M--->调用Hibernate的API
核心API: Configuration-->SessionFactory-->Session-->Transaction
|-->Query
Session内部封装Connection,提供的CRUD依赖于主键
进行非主键的查询：Query
Query query=session.createQuery(HQL);
查询employee中的所有数据
SQL: select * from employee(表名);
HQL: from Employee(类名);
根据面向对象的思想，一张表就是一个类，表和类在映射文件中对应，所以from后面是类名而不是表名。因为通过映射文件，表当中的一行数据hibernate会自动封装成对应的对象，所以HQL无须select *
查询employee表中名字叫calm的员工
SQL: select * from employee where ename='calm';
HQL: from Employee as e where e.ename='calm'
建议：在使用HQL执行条件查询时，要为类提供别名
HQL特点
1.类似于SQL
2.from 类名
3.可以有也可以没有select
4.在进行条件查询的时候要为类取别名 别名.属性名
查询集合： query.list();
单独对象：query.uninqueResult()
HQL 的基础开发
1.查询工资为300到600的员工
SQL：关键字between ....and /not between ...and
SQL: select * from t_employee where t_salary between 300 and 600;
HQL: from Employee as e where e.salary between 300 and 600;
2.查询工资为100,300,600的员工
SQL:关键字 in /not in
3.查询工资为200并且名字叫bobs
SQL:关键字 and/ or not
4.查询以xiao开头的名字
sql：关键字 like 'xiao%'
5.查询没有工资的员工
SQL:关键字 is null/ is not null
select * from t_employee where t_salary is null;
sql不能写等于null 但是hibernate可以写等于null
HQL的投射(投影)查询 Project查询，在HQL中加入了select关键字的查询
HQL from Employee --》每一行封装成一个Employee对象(通过映射文件)
List<Employee> emps=query.list()
HQL hql=select e.name,e.salary from Employee as e;
Query query=session.createQuery(hql);
没有返回一整行的数据无法封装成Employee,hibernate会将需要获得的数据用Object[]封装
List<Object[]> emps=query.list();
如果查询的是一个结果，hibernate通过query.list()封装成一个List<Object>对象。
聚合函数 sum(),max(),min(),avg(),count()
HQL 也可以使用聚合函数
sql:select max(t_salary),min(t_salary) from employee;
Hql:select e.dept.id, max(e.salary),min(e.salary),avg(e.salary)
from Employee as e group by e.dept.id;
平均工资大于300的部门的平均工资和最大工资
select e.dept.id, max(e.salary),avg(e.salary)
from Employee as e group by e.dept.id having avg(e.salary)>300;
隐式多表连接:通过关系属性的多表连接
缺点：可能有多表连接，发送多条sql语句从而降低了系统效率
查询bobs所在的部门
from Dept as d where d.emps.name='bobs'; hibernate3.2版本之前可以使用
from Dept as d join fetch d.emps as e where e.name='bobs'; hibernate3.2版本之后
如果hql中加入了join关键字，hibernate不能自动将一行数据封装成一个对象，必须加入关键字fetch
使用隐士对表连接的时候注意关系属性的类型。
没有雇员的部门 在hql当中判断集合是否为null可以使用is empty
from Dept as d where d.emps is empty
显示多表连接：通过join关键字实现多表查询，通过一条sql语句就能完成多表查询、
等值连接 inner join（Oracle9i可以省略）
SQL：select e.*,d.* from g_employee e,g_dept d where e.d_id=d.t_id;
select e.*,d.* from g_employee e inner join g_dept d on e.d_id=d.t_id;
HQL：from Employee as e inner join e.dept
因为加入了join关键词，不能封装成对象，每一行数据由Employee和Dept对象组成
List<Object[]> emps=query.list();
from Dept as d inner join fetch d.emps;
List<Dept> depts=query.list();
结果会有重复数据
Set:去重，不能保留插入数据的顺序
List:保留数据的顺序，不能去重
LinkedSet:可以保留顺序，同时可以过滤重复
List <Dept> depts=query.list();
LinkedHashSet<Dept> deptsList=new LinkedHashSet<Dept>(depts);
驱动表 left outer join 匹配表 (左外连接，保留左边表的完整性)
from Employee as e left outer join fetch e.dept
匹配表 right outer join 驱动表(右外连接,保留右边表的完整性)
注意：右外连接hibernate不提供fetch关键词
全连接 full join hibernate不支持full join
hibernate的分页
Oracle:rownum
Mysql:limit
Query query=session.createQuery("from Employee");
query.setFirstResult(0);//开始显示的记录，从0开始
query.setMaxResult(3);//设置每页的记录数
query.list();
Bulk update HQL提供的修改和删除的方法
Query 对象实现对数据的 修改和删除
SQL:update g_employee set name=xxx where xxx;
String hql="update Employee as e set e.name='xxxx' where e.id=1 ";//修改
SLQ :delete from g_employee where t_id=1;
HQL hql="delete Employee as e where e.id=1 ";//删除
query对象的修改和删除与Session提供的delete(),和update()的区别
1.Bulk update效率高
2.Bulk update不会涉及缓存
3.Bulk update不会涉及级联
4.Bulk update不更新乐观锁
1.提供实体类Dept.java和Employee.java
package com.jsu.hb.pojo;
import java.util.HashSet;
import java.util.Set;
public class Dept {
private Integer id;
private String dname;
private String dno;
private Set<Employee> emps = new HashSet<Employee>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getDname() {
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public String getDno() {
return dno;
}
public void setDno(String dno) {
this.dno = dno;
}
public Set<Employee> getEmps() {
return emps;
}
public void setEmps(Set<Employee> emps) {
this.emps = emps;
}
}
Employee.java
package com.jsu.hb.pojo;
import java.util.Date;
public class Employee {
private Integer id;
private String name;
private Date birthday;
private String email;
private double salary;
private Dept dept;
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 Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public Dept getDept() {
return dept;
}
public void setDept(Dept dept) {
this.dept = dept;
}
}
2.建表
create table g_dept(
t_id integer primary key,
t_dname varchar2(20),
t_dno varchar2(20)
)
create table g_employee(
t_id integer primary key,
t_name varchar2(25),
t_birthday date,
t_salary number(12,2),
t_email varchar2(50),
d_id integer references g_dept(t_id)
)
insert into g_dept(t_id,t_dname,t_dno) values (1,'dev','001');
insert into g_dept(t_id,t_dname,t_dno) values (2,'train','002');
insert into g_dept(t_id,t_dname,t_dno) values (3,'market','003');
insert into g_dept(t_id,t_dname,t_dno) values (4,'game','004');
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (1,'bobs',to_date('2012-1-11','yyyy-mm-dd'),'bobs@b',100.0,1);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (2,'scott',to_date('2010-10-11','yyyy-mm-dd'),'scott@b',300.0,1);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (3,'tiger',to_date('2008-2-11','yyyy-mm-dd'),'tiger@b',400.0,2);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (4,'lucy',to_date('2009-3-11','yyyy-mm-dd'),'lucy@b',600.0,2);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (5,'lily',to_date('2012-4-11','yyyy-mm-dd'),'lily@b',1000.0,3);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (6,'tom',to_date('2001-10-11','yyyy-mm-dd'),'tom@b',700.0,3);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (7,'black',to_date('2001-10-11','yyyy-mm-dd'),'black@b',200.0,null);
commit
3.提供映射文件query.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"> <hibernate-mapping package="com.jsu.hb.pojo"> <class name="Dept" table="g_dept"> <id name="id" column="t_id"> <generator class="increment"></generator> </id> <property name="dname" column="t_dname"></property> <property name="dno" column="t_dno"></property> <!-- 关系属性 --> <set name="emps" cascade="all" inverse="true"> <key column="d_id"></key> <one-to-many class="Employee"></one-to-many> </set> </class> <class name="Employee" table="g_employee"> <id name="id" column="t_id"> <generator class="increment"></generator> </id> <property name="name" column="t_name"></property> <property name="birthday" column="t_birthday" type="java.util.Date"></property> <property name="email" column="t_email"></property> <property name="salary" column="t_salary"></property> <!-- 双向关系是添加关系属性 --> <many-to-one name="dept" class="Dept" cascade="save-update" column="d_id"></many-to-one> </class> </hibernate-mapping>
4.在hibernate.cfg.xml中对映射文件进行注册
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- show_sql:是否显示hibernate执行的SQL语句，默认为false --> <property name="show_sql">true</property> <!-- show_sql:是否显示hibernate执行格式化输出的SQL语句，默认为false --> <property name="format_sql">true</property> <!-- 配置与数据库连接的参数 --> <property name="connection.driver_class">oracle.jdbc.OracleDriver</property> <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:oracle</property> <property name="connection.username">scott</property> <property name="connection.password">tiger</property> <!-- 2.自身属性相关的配置 dialect:方言 hibernate根据dialect的配置进行特定数据性能方面的调优 --> <property name="dialect">org.hibernate.dialect.Oracle9iDialect</property> <mapping resource="com/jsu/hb/pojo/query.hbm.xml"></mapping> </session-factory> </hibernate-configuration>
5.提供工具类HibernateUtil.java
package com.jsu.hb.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sf;
private static ThreadLocal<Session> tl= new ThreadLocal<Session>();
static{
try{
Configuration cfg = new Configuration();
cfg.configure();
sf=cfg.buildSessionFactory();
}catch(Exception e){
e.printStackTrace();
}
}
public static Session openSession(){
return sf.openSession();
}
public static Session getCurrentSession(){
Session session = tl.get();//先从储存的线程中查找
if(session==null){
session=openSession();
tl.set(session);
return session;
}
return session;
}
}
6.提供测试类TestQuery.java
package com.jsu.hb.test;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import com.jsu.hb.pojo.Dept;
import com.jsu.hb.pojo.Employee;
import com.jsu.hb.util.HibernateUtil;
public class TestQuery {
//hql查找所有
@Test
public void queryAll(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Employee";
Query query = session.createQuery(hql);
List<Employee> emps = query.list();
for(Employee e: emps){
System.out.println(e.getName());
}
tx.commit();
}
@Test
public void queryByName(){
String name="tom";
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Employee as e where e.name=?";
Query query = session.createQuery(hql);
query.setString(0, "tom");// 为占位符赋值，从0开始
Employee e =(Employee)query.uniqueResult();// 返回单个对象
System.out.println(e.getName()+" : "+e.getEmail()+" : "+e.getBirthday()+" : "+e.getSalary());
tx.commit();
}
@Test
public void testNull(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Employee as e where e.dept.id=null";
Query query = session.createQuery(hql);
Employee e =(Employee)query.uniqueResult();
System.out.println(e.getName());
tx.commit();
}
@Test
public void testLike(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Employee as e where e.name like'xiao%'";
Query query = session.createQuery(hql);
Employee e =(Employee)query.uniqueResult();
System.out.println(e.getName());
tx.commit();
}
@Test
public void testAggregation(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "select e.dept.id,max(e.salary),avg(e.salary),min(salary) "+
"from Employee as e group by e.dept.id having avg(e.salary)>300";
Query query = session.createQuery(hql);
List<Object[]> emps = query.list();
for(Object[] obj:emps){
System.out.println(" 最大工资为："+obj[0]+" 平均工资为： "+obj[1]+" 最小工资为： "+obj[2]);
}
}
@Test
public void testHiddenMT(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Dept as d join fetch d.emps as e where e.name='bobs'";
Query query = session.createQuery(hql);
Dept d = (Dept)query.uniqueResult();
System.out.println("部门名称："+d.getDname());
tx.commit();
}
@Test
public void testEqualsValueLinked(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Dept as d inner join fetch d.emps";
Query query = session.createQuery(hql);
List<Dept> depts = query.list();
LinkedHashSet<Dept> deptSet = new LinkedHashSet<Dept>(depts);
for(Dept d:deptSet){
System.out.println(d.getDname());
}
}
@Test
public void testLinked(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Employee as e left outer join fetch e.dept";
Query query = session.createQuery(hql);
List<Employee> emps = query.list();
LinkedHashSet<Employee> deptSet = new LinkedHashSet<Employee>(emps);
for(Employee e :deptSet){
System.out.println(e.getName());
}
}
public void testQuery() {
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
// 开发dev部门的所有员工
String hql = "from Employee as e where e.dept.dname='dev'";
Query query = session.createQuery(hql);
/* 每个员工的部门名称 */
List<Employee> emps = query.list();
for (Employee e : emps) {
System.out.println(e.getName() + " : " + e.getDept().getDname());
}
tx.commit();
}
public void testC() {
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Dept as d where d.emps.name='bobs' ";
String hql1 = "from Dept as d join fetch d.emps as e where e.name='bobs'";
String hql2 = "from Dept as d where d.emps is empty";// 不用迭代集合
Query query = session.createQuery(hql2);
Dept d = (Dept) query.uniqueResult();
System.out.println(d.getDname());
tx.commit();
}
public void queryDept() {
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql1 = "from Dept as d inner join fetch d.emps";
Query query = session.createQuery(hql1);
List<Dept> depts = query.list();
LinkedHashSet<Dept> depts1=new LinkedHashSet<Dept>(depts);
for (Dept d : depts1) {
Set<Employee> emps = d.getEmps();
for (Employee e : emps) {
System.out.println(d.getDname() + " " + e.getName());
}
}
tx.commit();
}
//hibernate分页
@Test
public void testPage(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "from Employee";
Query query = session.createQuery(hql);
query.setFirstResult(0);
query.setMaxResults(3);
List<Employee> emps =query.list();
System.out.println(emps.size());
tx.commit();
}
//修改
@Test
public void testUpdate(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "update Employee as e set e.name='haoren' where e.id=1";
Query query = session.createQuery(hql);
query.executeUpdate();
tx.commit();
}
//删除
@Test
public void testBulk(){
Session session = HibernateUtil.getCurrentSession();
Transaction tx = session.getTransaction();
tx.begin();
String hql = "delete Employee as e where t_id=8";
Query query = session.createQuery(hql);
query.executeUpdate();
tx.commit();
}
}