Hibernate Criteria查询

虽然可以自己写Sql,但在程序中需要动态生成Sql语句时，where子句中条件是动态产生时，使用Criteria是再好不过的选择。

先看例子： 

        Criteria criteria=session.createCriteria(Product.class);
        Criterion criterion1=Restrictions.between("id", 10, 15); //Criterion接口
     	criteria.add(criterion1);
        List<Product> list=criteria.list(); 
	for(Product p:list){
	     System.out.println(p.getId()+" "+p.getName());
	}

输出:

Hibernate: 
    select
        this_.ID as ID4_0_,
        this_.NAME as NAME4_0_,
        this_.PRICE as PRICE4_0_,
        this_.DESCRIPTION as DESCRIPT4_4_0_ 
    from
        hib.product this_ 
    where
        this_.ID between ? and ?
10 台灯3
11 台灯2
15 台灯

可以使用方法链，因为add()后仍返回当前Criteria对象。如下

List<Product> list=session.createCriteria(Product.class).add(Restrictions.between("id",10,15)).list();　　

1.排序 criteria.addOrder(Order.desc("id"));

2.分页

criteria.setMaxResults(3);
criteria.setFirstResult(3);

mysql产生如下语句：

Hibernate: 
    select
        this_.ID as ID4_0_,
        this_.NAME as NAME4_0_,
        this_.PRICE as PRICE4_0_,
        this_.DESCRIPTION as DESCRIPT4_4_0_ 
    from
        hib.product this_ limit ?,
        ?

oracle则产生:

select * from(
      select row_.*,rownum rownum_
      from(
           原始sql语句
      ) row_
     where rownum<=?
)
where rownum_>?

　

3.单条记录

criteria.setMaxResults(1);
Product p=(Product)criteria.uniqueResult();

 4.在关联对象上增加条件

Criteria criteria=session.createCriteria(Product.class);
criteria.createCriteria("category").add(Restrictions.between("id",35, 40));
//Product和Category是多对一的关系
//Prodcut类中成员 Category category;
		

　输出：

    select
        this_.ID as ID4_1_,
        this_.CATEGORY_ID as CATEGORY2_4_1_,
        this_.NAME as NAME4_1_,
        this_.PRICE as PRICE4_1_,
        this_.DESCRIPTION as DESCRIPT5_4_1_,
        category1_.ID as ID3_0_,
        category1_.NAME as NAME3_0_,
        category1_.DESCRIPTION as DESCRIPT3_3_0_ 
    from
        hib.pro this_ 
    inner join
        hib.category category1_ 
            on this_.CATEGORY_ID=category1_.ID 
    where
        category1_.ID between ? and ?

　使用内连接查询。如果是一的一方中增加对多的一方的条件，则结果是类似的。

Criteria criteria=session.createCriteria(Category.class);
criteria.createCriteria("products").add(Restrictions.between("id",1,2));
criteria.list();

输出：

Hibernate: 
    select
        this_.ID as ID3_1_,
        this_.NAME as NAME3_1_,
        this_.DESCRIPTION as DESCRIPT3_3_1_,
        product1_.ID as ID4_0_,
        product1_.CATEGORY_ID as CATEGORY2_4_0_,
        product1_.NAME as NAME4_0_,
        product1_.PRICE as PRICE4_0_,
        product1_.DESCRIPTION as DESCRIPT5_4_0_ 
    from
        hib.category this_ 
    inner join
        hib.pro product1_ 
            on this_.ID=product1_.CATEGORY_ID 
    where
        product1_.ID between ? and ?

5.统计函数查询

criteria.setProjection(Projections.max("price"));
Float f=(Float)criteria.uniqueResult();
System.out.println(f);

6.多个统计值

	Criteria criteria=session.createCriteria(Product.class);
        ProjectionList proList=Projections.projectionList();
        proList.add(Projections.max("price"));
        proList.add(Projections.min("price"));
	criteria.setProjection(proList);
        Object[] values=(Object[])criteria.uniqueResult();

7.分组统计

	Criteria criteria=session.createCriteria(Product.class);
        ProjectionList proList=Projections.projectionList();
        proList.add(Projections.max("price"));
        proList.add(Projections.min("price"));
        proList.add(Projections.rowCount());
        proList.add(Projections.groupProperty("category"));//注意这里都是指POJO类的属性名，而不是数据库列名
	criteria.setProjection(proList);
        List<Object[]> values=criteria.list();

8.使用别名，

  proList.add(
       Projections.alias(
                Projections.max("price"),"maxp")	//别名的好处是下文可以用别名来限定条件
  );

或者：  proList.add( Projections.max("price").as("maxp"));
9.投影查询，限定列

        ProjectionList proList=Projections.projectionList();
        proList.add(Property.forName("price"));
        proList.add(Property.forName("id"));
	criteria.setProjection(proList);

10.使用org.hibernate.criterion.Property.forName()方法实现分组统计
proList.add(Property.forName("price").max()); 
proList.add(Property.forName("category").group().as("c"));

 11.使用DetachedCriteria（不与Session对象绑定，独立）

               //表现层，保存用户的动态查询条件
		DetachedCriteria dc=DetachedCriteria.forClass(Product.class);
		dc.add(Restrictions.between("id", 1, 5))
			.add(Restrictions.like("name", "台"));
		dc.addOrder(Order.desc("id"));
		//业务逻辑层与当前Session绑定
		//获取，开启session
		Criteria criteria=dc.getExecutableCriteria(session);
		List values=criteria.list();

12.根据示例对象查询(QBE)

		Product p1=new Product();
		p1.setName("台");
        	Criteria criteria=session.createCriteria(Product.class);
		criteria.add(Example.create(p1));
		List values=criteria.list();