hibernate查询&抓取策略优化机制

　　@Test ???????//来3个客户，30个联系人 ???????public void demo1(){ ???????????Session session=HibernateUtils.getCurrentSession(); ???????????Transaction tx=session.beginTransaction(); ???????????Customer customer=new Customer(); ???????????customer.setCust_name("小白"); ???????????for(int i=0;i<10;i++){ ???????????????LinkMan linkMan=new LinkMan(); ???????????????linkMan.setLkm_name("白白"+i); ???????????????linkMan.setCustomer(customer); ???????????????customer.getSets().add(linkMan); ???????????????session.save(linkMan); ???????????} ???????????session.save(customer); ???????????????tx.commit(); ???????}

@Test ???????//HQL简单查询,一个简单的查询 ???????public void demo2(){ ???????????Session session=HibernateUtils.getCurrentSession(); ???????????Transaction tx=session.beginTransaction(); ???????????Query query = session.createQuery("from Customer c");//这个Customer是类名 ???????????List<Customer> list = query.list(); ???????????for (Customer customer : list) { ???????????????System.out.println(customer); ???????????} ???????????tx.commit(); ???????}

@Test ???????//HQL排序查询,降序 ???????public void demo3(){ ???????????Session session=HibernateUtils.getCurrentSession(); ???????????Transaction tx=session.beginTransaction(); ???????????//升序：asc(默认) ?降序：desc ???????????Query query = session.createQuery("from Customer order by cust_id desc");//这个Customer是类名 ???????????List<Customer> list = query.list(); ???????????for (Customer customer : list) { ???????????????System.out.println(customer); ???????????} ???????????tx.commit(); ???????}

@Test ???????//HQL ???????public void demo4(){ ???????????Session session=HibernateUtils.getCurrentSession(); ???????????Transaction tx=session.beginTransaction(); ???????????//只有一个条件 ???????/*Query query = session.createQuery("from Customer where cust_name=?");//这个Customer是类名 ???????query.setParameter(0, "小花");*/ ???????????//多个条件查询 ???????/*Query query = session.createQuery("from Customer where cust_source=? and cust_name like ?"); ???????query.setParameter(0, "朋友介绍"); ???????query.setParameter(1, "%白");*/ ???????????//二 按名称绑定 ???????????Query query=session.createQuery("from Customer where cust_source = :a and cust_name like :b"); ???????????query.setParameter("a","网络推广"); ???????????query.setParameter("b","%紫"); ???????????List<Customer> list = query.list(); ???????????for (Customer customer : list) { ???????????????System.out.println(customer); ???????????} ???????????tx.commit(); ???????}

@Test ???????/** ????????* 投影查询 ????????*/ ???????public void demo5(){ ???????????Session session=HibernateUtils.getCurrentSession(); ???????????Transaction tx=session.beginTransaction(); ???????????//投影查询 单个属性 ???????/*List<Object> list =session.createQuery("select c.cust_name from Customer c").list(); ???????for (Object object : list) { ???????????System.out.println(object); ???????}*/ ???????????//这里会包含多种类型，用数组接收,查到两列的值了 ???????/*List<Object[]> list=session.createQuery("select c.cust_name,c.cust_source from Customer c").list(); ???????for (Object[] objects : list) { ???????????System.out.println(Arrays.toString(objects)); ???????}*/ ???????????//查询多个属性，封装到对象里面 ???????????List<Customer> list=session.createQuery("select new Customer(cust_id,cust_name,cust_source) from Customer").list(); ???????????for (Customer customer : list) { ???????????????System.out.println(customer); ???????????} ???????????tx.commit(); ???????}

@Test ???????/** ????????* 分页查询 ????????*/ ???????public void demo6(){ ???????????Session session=HibernateUtils.getCurrentSession(); ???????????Transaction tx=session.beginTransaction(); ???????????Query query = session.createQuery("from LinkMan"); ???????????query.setFirstResult(0); ???????????query.setMaxResults(3);//每页显示的条数 ???????????List<LinkMan> list = query.list(); ???????????for (LinkMan linkMan : list) { ???????????????//要在LinkMan实体类中加上toString ???????????????System.out.println(linkMan); ???????????} ???????????tx.commit(); ???????}

@Test ???????public void demo8(){ ???????????//根据客户来源来统计它的个数 ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ???????//既有String类型又有Long类型，用object类型接收 ???// ???List<Object[]> list=session.createQuery("select cust_source,count(*) from Customer group by cust_source").list(); ???????//根据客户来源统计个数大于等于2的 ???????List<Object[]> list=session.createQuery("select cust_source,count(*) from Customer group by cust_source having count(*)>=2").list(); ???????for (Object[] ?objects:list) { ???????????System.out.println(Arrays.toString(objects)); ???????} ???????tx.commit(); ???}

 ???@Test ???/** ????* HQL的多表查询 ????*/ ???public void demo9(){ ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ???????/*List<Object[]> list = session.createQuery("from Customer c inner join c.sets").list(); ???????for (Object[] obj: list ????????????) { ???????????System.out.println(Arrays.toString(obj)); ???????}*/ ???????//迫切内链接 ???????List<Customer> list = session.createQuery("select distinct c from Customer c inner join fetch c.sets").list(); ???????for (Customer customers: list ????????????) { ???????????System.out.println(customers); ???????} ???????tx.commit(); ???}

 @Test ???/** ????* 简单查询 ????*/ ???public ?void demo1(){ ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ??????Criteria criteria= session.createCriteria(Customer.class); ???????List<Customer> list = criteria.list(); ???????for(Customer customer:list){ ??????????System.out.println(customer); ??????} ???????tx.commit(); ???}

 @Test ???/** ????* 排序查询 ????*/ ???public void demo2(){ ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ???????Criteria criteria = session.createCriteria(Customer.class); ???????criteria.addOrder(Order.desc("cust_id"));//asc升序 ??desc降序 ???????List<Customer> list = criteria.list(); ???????for(Customer customer:list){ ???????????System.out.println(customer); ???????} ???????tx.commit(); ???}

 ?@Test ???/** ????* 分页查询 ????*/ ???public void demo3(){ ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ???????Criteria criteria = session.createCriteria(LinkMan.class); ???????criteria.setFirstResult(0); ???????criteria.setMaxResults(10); ???????List<LinkMan> list = criteria.list(); ???????for(LinkMan linkMan:list){ ???????????System.out.println(linkMan); ???????} ???????tx.commit(); ???}

 @Test ???/** ????* 条件查询 ????*/ ???public void demo4(){ ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ???????Criteria criteria = session.createCriteria(Customer.class); ???????/** ????????* = ???????eq ????????* > ???????gt ????????* >= ??????ge ????????* < ???????lt ????????* <= ??????le ????????* <> ??????ne ????????* like ????????*/ ???????criteria.add(Restrictions.eq("cust_source","广告")); ???????criteria.add(Restrictions.like("cust_name","%白")); ???????List<Customer> list = criteria.list(); ???????for(Customer customer:list){ ???????????System.out.println(customer); ???????} ???????tx.commit(); ???}

 @Test ???/** ????* 统计查询， ??一般还是用HQL的，QBC的不常用 ????*/ ???public void demo5(){ ???????Session session=HibernateUtils.getCurrentSession(); ???????Transaction tx=session.beginTransaction(); ???????Criteria criteria = session.createCriteria(Customer.class); ???????criteria.setProjection(Projections.rowCount()); ???????Long result= (Long)criteria.uniqueResult(); ???????System.out.println(result); ???????tx.commit(); ???}

 @Test ???/** ????* 离线条件查询,在后期的案例中会省很大的时间(相比原来拼接sql语句) ????*/ ???public void demo6(){ ???????DetachedCriteria dc = DetachedCriteria.forClass(Customer.class); ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction tx = session.beginTransaction(); ???????Criteria criteria = dc.getExecutableCriteria(session); ???????List<Customer> list = criteria.list(); ???????for (Customer customer:list ????????????) { ???????????System.out.println(customer); ???????} ???????tx.commit(); ???}