Hibernate07_Hibernate Query Language

爱被打了一巴掌 2022-11-24 16:21 146阅读 0赞

**Hibernate07\_Hibernate Query Language**

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例1：

String hql = "from People";
    Query query = session.createQuery(hql);
    List<People> list = query.list();
    for(People people : list) { 
    	System.out.println(people);
    }

People(id=1, name=张三, money=1000.0)
    People(id=2, name=李四, money=2000.0)
    People(id=3, name=王五, money=3000.0)
    People(id=4, name=小明, money=4000.0)
    People(id=5, name=小红, money=3000.0)
    People(id=6, name=小李, money=2000.0)
    People(id=7, name=BLU, money=3500.0)
    People(id=8, name=lily, money=4500.0)
    People(id=9, name=mary, money=5500.0)

例2（分页查询）：  
分页查询可以通过调用query的方法来完成：

setFirstResult()	设置起始下标（从0开始）
    setMaxResult()	设置截取长度

String hql = "from People";
    Query query = session.createQuery(hql);
    query.setFirstResult(1);
    query.setMaxResults(3);
    List<People> list = query.list();
    for(People people : list) { 
    	System.out.println(people);
    }

People(id=2, name=李四, money=2000.0)
    People(id=3, name=王五, money=3000.0)
    People(id=4, name=小明, money=4000.0)

例3（where条件查询）：

String hql = "from People where id = 7";
    Query query = session.createQuery(hql);
    People people = (People) query.list().get(0);
    System.out.println(people);

People(id=7, name=BLU, money=3500.0)

**注：通过以下两种方式都可以查出一条结果的值，但是用 list() 方法查出来的值不能为空，否则会报数组越界异常：java.lang.IndexOutOfBoundsException: Index: 0, Size: 0**

People people = (People) query.list().get(0);

People people = (People) query.uniqueResult();

例4（模糊查询）：

String hql = "from People where name like '%小%'";
    Query query = session.createQuery(hql);
    List<People> list = query.list();
    for(People people : list) { 
    	System.out.println(people);
    }

People(id=4, name=小明, money=4000.0)
    People(id=5, name=小红, money=3000.0)
    People(id=6, name=小李, money=2000.0)

例5（order by）asc/desc：

String hql = "from People order by id desc";
    Query query = session.createQuery(hql);
    List<People> list = query.list();
    for(People people : list) { 
    	System.out.println(people);
    }

People(id=9, name=mary, money=5500.0)
    People(id=8, name=lily, money=4500.0)
    People(id=7, name=BLU, money=3500.0)
    People(id=6, name=小李, money=2000.0)
    People(id=5, name=小红, money=3000.0)
    People(id=4, name=小明, money=4000.0)
    People(id=3, name=王五, money=3000.0)
    People(id=2, name=李四, money=2000.0)
    People(id=1, name=张三, money=1000.0)

例6（查询实体属性）：

String hql = "select name from People where id = 7";
    Query query = session.createQuery(hql);
    String name = (String) query.uniqueResult();
    System.out.println(name);

BLU

例7（占位符）：

String hql = "from People where name = :name";
    Query query = session.createQuery(hql);
    query.setString("name", "BLU");
    People people = (People) query.uniqueResult();
    System.out.println(people);

People(id=7, name=BLU, money=3500.0)

例8（级联查询）：

String hql1 = "from Customer where name = :name";
    Query query1 = session.createQuery(hql1);
    query1.setString("name", "张三");
    Customer customer = (Customer) query1.uniqueResult();	
    String hql2 = "from Orders where customer = :customer";
    Query query2 = session.createQuery(hql2);
    query2.setEntity("customer", customer);
    List<Orders> list = query2.list();
    for(Orders orders : list) { 
    	System.out.println(orders);
    }

Orders [id=1, name=订单1]
    Orders [id=2, name=订单2]
    Orders [id=4, name=订单3]