Hibernate（八）

三套查询之Criteria查询

完全面向对象的，不需要写任可查询语句.

1.查询所有的学生

     //1.查询所有的学生
     @Test
     public void test1(){
         Criteria criteria = session.createCriteria(Student.class);
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getId()+student.getName());
         }
 
         Criteria criteria2 = session.createCriteria("com.rong.entity.group.Student");
         List<Student> list2 = criteria2.list();
         for (Student student : list2) {
             System.out.println(student.getId()+student.getName());
         }
     }

2.添加查询条件

add(Criterion criterion) : 添加查询条件.
Criterion : 代表一个查询条件.
Restrictions工具类，专门负责生成查询条件对象，它把where部分都改成了静态方法。
sqlRestriction(String sql) : 生成查询条件的万能方法.
Property工具类，专门负责生成查询条件对象.
Propery.forName("属性名").xxx()

     //2.添加查询条件
     @Test
     public void test2(){
         //1.添加一个
         Criteria criteria = session.createCriteria(Student.class);
         criteria=criteria.add(Restrictions.like("name", "%ab%"));
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getId()+student.getName());
         }
         //2.添加多个
         Criteria criteria2 = session.createCriteria(Student.class);
         criteria2.add(Restrictions.like("name", "%a%"));
         criteria2.add(Restrictions.between("java", 60, 100));
         List<Student> list2 = criteria2.list();
         for (Student student : list2) {
             System.out.println(student.getId()+student.getName());
         }
         System.out.println("===================================");
         Criteria criteria3 = session.createCriteria(Student.class);
         criteria3.add(Property.forName("name").like("%p%"));
         criteria3.add(Property.forName("math").between(85, 100));
         List<Student> list3 = criteria3.list();
         for (Student student : list3) {
             System.out.println(student.getId()+student.getName()
                                 +student.getMath());
         }
     }

3.添加自己的sql

     //3.添加自己的sql
     @Test
     public void test3(){
         Criteria criteria = session.createCriteria(Student.class);
         criteria.add(Restrictions.sqlRestriction("length(name)>4 and name like '%a%'"));
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getId()+student.getName());
         }
     }

4.排序

addOrder(Order order) : 添加排序.
Order.asc("属性名") | Order.desc("属性名")
Property.forName("age").asc()|Property.forName("age").desc()

     //4.排序
     @Test
     public void test4(){
         //第一种方式
         Criteria criteria = session.createCriteria(Student.class);
         criteria.add(Restrictions.lt("id", 10));
         criteria.addOrder(Order.asc("java"));//升序
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getId()+student.getName()+student.getJava());
         }
         Criteria criteria2 = session.createCriteria(Student.class);
         criteria2.add(Restrictions.gt("id", 90));
         criteria2.addOrder(Order.desc("math"));//降序
         List<Student> list2 = criteria2.list();
         for (Student student : list2) {
             System.out.println(student.getId()+student.getName()+student.getMath());
         }
         //第二种方式
         Criteria criteria3 = session.createCriteria(Student.class);
         List<Student> list3 = criteria3.addOrder(Property.forName("java").asc()).list();
         for (Student student : list3) {
             System.out.println(student.getId()+student.getName()+student.getJava());
         }
         Criteria criteria4 = session.createCriteria(Student.class);
         List<Student> list4 = criteria4.addOrder(Property.forName("java").desc()).list();
         for (Student student : list4) {
             System.out.println(student.getId()+student.getName()+student.getJava());
         }
     }

5.查询一列

setProjection(Projection projection): 查询哪些列.
Projection : 代表一列
ProjectionList : 代表多列
Projections : 专门创建Projection | ProjectionList

     //5.查询一列
     @Test
     public void test5(){
         Criteria criteria = session.createCriteria(Student.class);
         criteria.setProjection(Projections.property("name"));
         List<String> list = criteria.list();
         for (String string : list) {
             System.out.println(string);
         }
     }

6.查询多列

     //6.查询多列
     @Test
     public void test6(){
         Criteria criteria = session.createCriteria(Student.class);
         ProjectionList pl = Projections.projectionList();
         pl.add(Projections.property("java"));
         pl.add(Projections.property("math"));
         criteria.setProjection(pl);
         //criteria.setProjection(Projections.projectionList().add(Projections.property("java"))
         //                                                    .add(Projections.property("math")));
         List<Object[]> list = criteria.list();
         for (Object[] objects : list) {
             for (Object object : objects) {
                 System.out.print(object+"\t");
             }
             System.out.println();
         }
     }

7.聚集函数

     //7.聚集函数
     @Test
     public void test7(){
         Criteria criteria = session.createCriteria(Student.class);
         criteria.setProjection(Projections.rowCount());
         criteria.add(Restrictions.between("id", 10, 20));
         Object rowCount = criteria.uniqueResult();
         System.out.println("id在10到20之间的数量为："+rowCount);
         Criteria criteria2 = session.createCriteria(Student.class);
         criteria2.setProjection(Projections.sum("java"));
         criteria2.add(Property.forName("id").between(1, 3));
         Object sum = criteria2.uniqueResult();
         System.out.println("id为1到3的java成绩总和为："+sum);
     }

8.分组

     //8.分组
     @Test
     public void test8(){
         Criteria criteria = session.createCriteria(Student.class);
         criteria.setProjection(Projections.projectionList().add(Projections.rowCount()).add(Projections.groupProperty("teacher.id")));
         List<Object[]> list = criteria.list();
         for (Object[] objects : list) {
             for (Object object : objects) {
                 System.out.println(object);
             }
         }
     }

9.通过老师id查询学生(使用别名查询)

setFetchMode(String associationPath, FetchMode mode): 抓取连接(join fetch)
FetchMode: 抓取模式
FetchMode.JOIN FetchMode.EAGER 立即查询
FetchMode.SELECT FetchMode.LAZY 延迟查询

     //9.通过老师id查询学生(使用别名查询)
     @Test
     public void test9(){
         Criteria criteria = session.createCriteria(Student.class);
         criteria.add(Restrictions.eq("teacher.tid", 1));
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getName()+student.getTeacher().getTid());
         }
         System.out.println("=============以下是通过别名查询================");
         Criteria criteria2 = session.createCriteria(Student.class);
         criteria2.createAlias("teacher", "t");
         criteria2.add(Restrictions.eq("t.id", 1));
         List<Student> list2 = criteria2.list();
         for (Student student : list2) {
             System.out.println(student.getName()+student.getTeacher().getTid());
         }
     }

 //setFetchMode: 抓取延迟的属性
         Criteria criteria3 = session.createCriteria(Student.class);
         criteria3.setFetchMode("teacher", FetchMode.JOIN);
         List<Student> list3 = criteria3.list();
         /*for (Student student : list3) {
             System.out.println(student.getName()+student.getTeacher().getTid());
         }*/

10.离线查询

离线查询 DetachedCriteria.
DetachedCriteria ：用它就可以定义一条查询语句. select * from stu_info.
用得时候需要与Session关联起来.
离线查询的主要作用就是为了做子查询. in 、not in(离线查询对象)

     //10.离线查询
     @Test
     public void test10(){
         DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Student.class);
         Criteria criteria = detachedCriteria.getExecutableCriteria(session);
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getId()+student.getName());
         }
     }

11.子查询

     //11.子查询
     @Test
     public void test11(){
         Criteria criteria = session.createCriteria(Student.class);
         criteria.add(Restrictions.in("id", new Object[]{1,2,3}));
         List<Student> list = criteria.list();
         for (Student student : list) {
             System.out.println(student.getId()+student.getName());
         }
         System.out.println("==================================");
         //离线查询作为子查询的一部分
         DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Student.class);
         detachedCriteria.setProjection(Projections.property("id"));
         detachedCriteria.add(Restrictions.between("id", 60, 90));
         Criteria criteria2 = session.createCriteria(Student.class);
         criteria2.add(Property.forName("id").in(detachedCriteria));
         List<Student> list2 = criteria2.list();
         for (Student student : list2) {
             System.out.println(student.getId()+student.getName());
         }
     }