1. HQL语法
1.1 基本语法
- 查全部
@Test
public void testFunc01() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " from Customer";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list);
transaction.commit();
session.close();
}
- 排序
// 升序
String hql = " from Customer order by cust_id asc ";
// 降序
String hql = " from Customer order by cust_id desc ";
- 条件查询
// 条件查询
@Test
public void testFunc03() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " from Customer where cust_id = ?";
Query query = session.createQuery(hql);
query.setParameter(0, 3l);
List list = query.list();
System.out.println(list);
transaction.commit();
session.close();
}
@Test
public void testFunc04() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " from Customer where cust_id = :cust_id";
Query query = session.createQuery(hql);
query.setParameter("cust_id", 1l);
List list = query.list();
System.out.println(list);
transaction.commit();
session.close();
}
- 分页查询
// 分页
@Test
public void testFunc05() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " from Customer";
Query query = session.createQuery(hql);
// 相当于 sql 中的 limit ?, ?
query.setFirstResult(1);
query.setMaxResults(1);
List list = query.list();
System.out.println(list);
transaction.commit();
session.close();
}
- 聚合查询
// sum 总条数
String hql = "select count(*) from Customer ";
// 求和
String hql = "select sum (cust_id) from Customer ";
// 求平均值
String hql = "select avg (cust_id) from Customer ";
// 求最大值
String hql = "select max (cust_id) from Customer ";
// 求最小值
String hql = "select min (cust_id) from Customer ";
Query query = session.createQuery(hql);
Number number = (Number) query.uniqueResult();
System.out.println(number);
- 投影查询
// 投影查询
@Test
public void testFunc07() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " select cust_name from Customer ";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list);
transaction.commit();
session.close();
}
@Test
public void testFunc08() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " select new Customer(cust_id, cust_name) from Customer ";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list);
transaction.commit();
session.close();
}
1.2 HQL多表查询
- 内连接
// 内连接：将连接两端的对象分别返回，放到数组中
@Test
public void testFunc09() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " from Customer c inner join c.linkMen";
Query query = session.createQuery(hql);
List list = query.list();
for (Object[] arr : list) {
System.out.println(Arrays.toString(arr));
System.out.println("---------");
}
System.out.println(list);
transaction.commit();
session.close();
}
- 迫切内连接：帮我们进行封装，返回值就是一个对象
// 迫切内连接
@Test
public void testFunc10() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql = " from Customer c inner join fetch c.linkMen";
Query query = session.createQuery(hql);
List list = query.list();
for (Customer customer : list) {
System.out.println(customer);
System.out.println("---------");
}
transaction.commit();
session.close();
}
- 左外连接
@Test
//HQL 左外连接 => 将连接的两端对象分别返回.放到数组中.
public void testFunc11(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
String hql = " from Customer c left join c.linkMen ";
Query query = session.createQuery(hql);
List list = query.list();
for(Object[] arr : list){
System.out.println(Arrays.toString(arr));
}
//----------------------------------------------------
tx.commit();
session.close();
}
- 右外连接
@Test
//HQL 右外连接 => 将连接的两端对象分别返回.放到数组中.
public void testFunc12(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
String hql = " from Customer c right join c.linkMen ";
Query query = session.createQuery(hql);
List list = query.list();
for(Object[] arr : list){
System.out.println(Arrays.toString(arr));
}
//----------------------------------------------------
tx.commit();
session.close();
}
2. Criteria查询（QBC）
- 基本查询
@Test
public void testFunc01() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
Criteria criteria = session.createCriteria(Customer.class);
List list = criteria.list();
System.out.println(list);
transaction.commit();
session.close();
}
- 条件查询
@Test
public void testFunc02() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
Criteria criteria = session.createCriteria(Customer.class);
// 体贴写法
criteria.add(Restrictions.idEq(1l));
// 通用条件
criteria.add(Restrictions.eq("cust_id", 1l));
Customer customer = (Customer) criteria.uniqueResult();
System.out.println(customer);
transaction.commit();
session.close();
}
- 分页查询 - 和HQL一样
@Test
public void testFunc03() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
Criteria criteria = session.createCriteria(Customer.class);
criteria.setFirstResult(1);
criteria.setMaxResults(1);
List list = criteria.list();
System.out.println(list);
transaction.commit();
session.close();
}
- 排序
@Test
public void testFunc04() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
Criteria criteria = session.createCriteria(Customer.class);
// 升序
criteria.addOrder(Order.asc("cust_od"));
// 降序
criteria.addOrder(Order.desc("cust_od"));
List list = criteria.list();
System.out.println(list);
transaction.commit();
session.close();
}
- 聚合函数查询
@Test
public void testFunc05() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
// 行数
Criteria criteria = session.createCriteria(Customer.class);
criteria.setProjection(Projections.rowCount());
System.out.println(criteria.list());
transaction.commit();
session.close();
}
3. 离线查询对象
// 离线查询
@Test
public void testFunc06() {
// web层
DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Customer.class);
// service层
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
// dao层
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
List list = criteria.list();
System.out.println(list);
transaction.commit();
session.close();
}
4. 查询优化-策略
4.1 类级别加载策略
@Test
// get方法 : 立即加载.执行方法时立即发送sql语句查询结果
public void testFunc01(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
// 在这句执行sql查询操作
Customer c = session.get(Customer.class, 1l);
System.out.println(c);
//----------------------------------------------------
tx.commit();
session.close();
}
@Test
// load方法(默认):是在执行时,不发送任何sql语句.返回一个对象.使用该对象时,才执行查询.
// 延迟加载: 仅仅获得没有使用.不会查询.在使用时才进行查询.
// 是否进行延迟加载: 可以通过在class元素上配置lazy属性来控制.
//lazy:true 加载时,不查询.使用时才查询，使用代理对象Customer$$来完完成数据库查询
//lazy:false 加载时立即查询.
public void fun2(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
Customer c = session.load(Customer.class, 1l);
//----------------------------------------------------
tx.commit();
session.close();
System.out.println(c);
}
// 配置文件
4.2 关联级别查询策略
- 集合策略
也就是根据Customer来获取LinkMan
配置文件Customer.hbm.xml
//关联级别 延迟加载 & 抓取策略
public class Demo {
//集合级别的关联
//fetch:select 单表查询
//lazy:true 使用时才加载集合数据.
@Test
public void fun1(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
Customer c = session.get(Customer.class, 2l);
Set linkMens = c.getLinkMens();//关联级别
System.out.println(linkMens);
//----------------------------------------------------
tx.commit();
session.close();
}
//集合级别的关联
//fetch:select 单表查询
//lazy:false 立即加载集合数据
@Test
public void fun2(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
Customer c = session.get(Customer.class, 2l);
Set linkMens = c.getLinkMens();//关联级别
System.out.println(linkMens);
//----------------------------------------------------
tx.commit();
session.close();
}
//集合级别的关联
//fetch:select 单表查询
//lazy:extra 极其懒惰.与懒加载效果基本一致. 如果只获得集合的size.只查询集合的size(count语句)
@Test
public void fun3(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
Customer c = session.get(Customer.class, 2l);
Set linkMens = c.getLinkMens();//关联级别
System.out.println(linkMens.size());
System.out.println(linkMens);
//----------------------------------------------------
tx.commit();
session.close();
}
//集合级别的关联
//fetch:join 多表查询
//lazy:true|false|extra 失效.立即加载.
@Test
public void fun4(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
Customer c = session.get(Customer.class, 2l);
Set linkMens = c.getLinkMens();//关联级别
System.out.println(linkMens.size());
System.out.println(linkMens);
//----------------------------------------------------
tx.commit();
session.close();
}
@Test
//fetch: subselect 子查询
//lazy: true 懒加载
public void fun5(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
String hql = "from Customer";
Query query = session.createQuery(hql);
List list = query.list();
for(Customer c:list){
System.out.println(c);
System.out.println(c.getLinkMens().size());
System.out.println(c.getLinkMens());
}
//----------------------------------------------------
tx.commit();
session.close();
}
@Test
//fetch: subselect 子查询
//lazy: false 立即加载
public void fun6(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
String hql = "from Customer";
Query query = session.createQuery(hql);
List list = query.list();
for(Customer c:list){
System.out.println(c);
System.out.println(c.getLinkMens().size());
System.out.println(c.getLinkMens());
}
//----------------------------------------------------
tx.commit();
session.close();
}
@Test
//fetch: subselect 子查询
//lazy: extra 极其懒惰
public void fun7(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
String hql = "from Customer";
Query query = session.createQuery(hql);
List list = query.list();
for(Customer c:list){
System.out.println(c);
System.out.println(c.getLinkMens().size());
System.out.println(c.getLinkMens());
}
//----------------------------------------------------
tx.commit();
session.close();
}
}
- 对象策略
配置文件 LinkMan.hbm.xml
根据LinkMan获得Customer
//关联级别 延迟加载 & 抓取策略
public class Demo2 {
@Test
//fetch:select 单表查询
//lazy:proxy
//customer-true 懒加载
public void fun1(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
LinkMan lm = session.get(LinkMan.class, 3l);
Customer customer = lm.getCustomer();
System.out.println(customer);
//----------------------------------------------------
tx.commit();
session.close();
}
@Test
//fetch:join 多表
//lazy: 失效
public void fun3(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
LinkMan lm = session.get(LinkMan.class, 3l);
Customer customer = lm.getCustomer();
System.out.println(customer);
//----------------------------------------------------
tx.commit();
session.close();
}
@Test
//fetch:select 单表查询
//lazy:proxy
//customer-false 立即加载
public void fun2(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
LinkMan lm = session.get(LinkMan.class, 3l);
Customer customer = lm.getCustomer();
System.out.println(customer);
//----------------------------------------------------
tx.commit();
session.close();
}
}
结论：全部使用默认值
- 批量抓取 - 提高效率
配置文件 Customer.hbm.xml
每次抓取三个LinkMan，减少sql操作
//抓取数量
public class Demo {
@Test
public void fun1(){
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//----------------------------------------------------
String hql = "from Customer ";
Query query = session.createQuery(hql);
List list = query.list();
for(Customer c:list){
System.out.println(c.getLinkMens());
}
//----------------------------------------------------
tx.commit();
session.close();
}
5. 使用离线查询DetachedCriteria，完成客户列表筛选功能
- CustomerListServlet
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String cust_name = request.getParameter("cust_name");
List list = null;
DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Customer.class);
if (cust_name != null && !"".equals(cust_name)) {
detachedCriteria.add(Restrictions.like("cust_name", "%" + cust_name + "%"));
list = customerService.getCustomerByDetachedCriteria(detachedCriteria);
System.out.println("-----条件查询-----" + cust_name);
} else {
list = customerService.getAll(detachedCriteria);
System.out.println("------全部查询-------");
}
// 将客户列表放到request域
request.setAttribute("list", list);
// 转发到list.jsp
request.getRequestDispatcher("/jsp/customer/list.jsp").forward(request, response);
}
- CustomerService 接口和 CustomerServiceImpl 实现类
public List getAll(DetachedCriteria detachedCriteria);
public List getCustomerByDetachedCriteria(DetachedCriteria detachedCriteria);
这里可以进行方法的抽取，只在servlet中进行离线DetachedCriteria 的条件组装即可，service和dao中不需要再修改方法，一个就够了
@Override
public List getAll(DetachedCriteria detachedCriteria) {
Session session = HibernateUtils.getCurrentSession();
// 打开事务
Transaction transaction = session.beginTransaction();
List list = customerDao.getAll(detachedCriteria);
transaction.commit();
return list;
}
@Override
public List getCustomerByDetachedCriteria(DetachedCriteria detachedCriteria) {
Session session = HibernateUtils.getCurrentSession();
Transaction transaction = session.beginTransaction();
List list = customerDao.getCustomerByDetachedCriteria(detachedCriteria);
transaction.commit();
return list;
}
- CustomerDao 接口和 CustomerDaoImpl 实现类
public List getAll(DetachedCriteria detachedCriteria);
public List getCustomerByDetachedCriteria(DetachedCriteria detachedCriteria);
@Override
public List getAll(DetachedCriteria detachedCriteria) {
Session session = HibernateUtils.getCurrentSession();
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
return criteria.list();
}
@Override
public List getCustomerByDetachedCriteria(DetachedCriteria detachedCriteria) {
Session session = HibernateUtils.getCurrentSession();
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
return criteria.list();
}