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  • 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     //1.查询所有的学生
 2     @Test
 3     public void test1(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         List<Student> list = criteria.list();
 6         for (Student student : list) {
 7             System.out.println(student.getId()+student.getName());
 8         }
 9         
10         Criteria criteria2 = session.createCriteria("com.rong.entity.group.Student");
11         List<Student> list2 = criteria2.list();
12         for (Student student : list2) {
13             System.out.println(student.getId()+student.getName());
14         }
15     }

     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()

     1     //2.添加查询条件
 2     @Test
 3     public void test2(){
 4         //1.添加一个
 5         Criteria criteria = session.createCriteria(Student.class);
 6         criteria=criteria.add(Restrictions.like("name", "%ab%"));
 7         List<Student> list = criteria.list();
 8         for (Student student : list) {
 9             System.out.println(student.getId()+student.getName());
10         }
11         //2.添加多个
12         Criteria criteria2 = session.createCriteria(Student.class);
13         criteria2.add(Restrictions.like("name", "%a%"));
14         criteria2.add(Restrictions.between("java", 60, 100));
15         List<Student> list2 = criteria2.list();
16         for (Student student : list2) {
17             System.out.println(student.getId()+student.getName());
18         }
19         System.out.println("===================================");
20         Criteria criteria3 = session.createCriteria(Student.class);
21         criteria3.add(Property.forName("name").like("%p%"));
22         criteria3.add(Property.forName("math").between(85, 100));
23         List<Student> list3 = criteria3.list();
24         for (Student student : list3) {
25             System.out.println(student.getId()+student.getName()
26                                 +student.getMath());
27         }
28     }

    3.添加自己的sql

     1     //3.添加自己的sql
 2     @Test
 3     public void test3(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         criteria.add(Restrictions.sqlRestriction("length(name)>4 and name like '%a%'"));
 6         List<Student> list = criteria.list();
 7         for (Student student : list) {
 8             System.out.println(student.getId()+student.getName());
 9         }
10     }

    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()

     1     //4.排序
 2     @Test
 3     public void test4(){
 4         //第一种方式
 5         Criteria criteria = session.createCriteria(Student.class);
 6         criteria.add(Restrictions.lt("id", 10));
 7         criteria.addOrder(Order.asc("java"));//升序
 8         List<Student> list = criteria.list();
 9         for (Student student : list) {
10             System.out.println(student.getId()+student.getName()+student.getJava());
11         }
12         Criteria criteria2 = session.createCriteria(Student.class);
13         criteria2.add(Restrictions.gt("id", 90));
14         criteria2.addOrder(Order.desc("math"));//降序
15         List<Student> list2 = criteria2.list();
16         for (Student student : list2) {
17             System.out.println(student.getId()+student.getName()+student.getMath());
18         }
19         //第二种方式
20         Criteria criteria3 = session.createCriteria(Student.class);
21         List<Student> list3 = criteria3.addOrder(Property.forName("java").asc()).list();
22         for (Student student : list3) {
23             System.out.println(student.getId()+student.getName()+student.getJava());
24         }
25         Criteria criteria4 = session.createCriteria(Student.class);
26         List<Student> list4 = criteria4.addOrder(Property.forName("java").desc()).list();
27         for (Student student : list4) {
28             System.out.println(student.getId()+student.getName()+student.getJava());
29         }
30     }

     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

     1     //5.查询一列
 2     @Test
 3     public void test5(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         criteria.setProjection(Projections.property("name"));
 6         List<String> list = criteria.list();
 7         for (String string : list) {
 8             System.out.println(string);
 9         }
10     }

    6.查询多列

     1     //6.查询多列
 2     @Test
 3     public void test6(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         ProjectionList pl = Projections.projectionList();
 6         pl.add(Projections.property("java"));
 7         pl.add(Projections.property("math"));
 8         criteria.setProjection(pl);
 9         //criteria.setProjection(Projections.projectionList().add(Projections.property("java"))
10         //                                                    .add(Projections.property("math")));
11         List<Object[]> list = criteria.list();
12         for (Object[] objects : list) {
13             for (Object object : objects) {
14                 System.out.print(object+"	");
15             }
16             System.out.println();
17         }
18     }

     7.聚集函数

     1     //7.聚集函数
 2     @Test
 3     public void test7(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         criteria.setProjection(Projections.rowCount());
 6         criteria.add(Restrictions.between("id", 10, 20));
 7         Object rowCount = criteria.uniqueResult();
 8         System.out.println("id在10到20之间的数量为："+rowCount);
 9         Criteria criteria2 = session.createCriteria(Student.class);
10         criteria2.setProjection(Projections.sum("java"));
11         criteria2.add(Property.forName("id").between(1, 3));
12         Object sum = criteria2.uniqueResult();
13         System.out.println("id为1到3的java成绩总和为："+sum);
14     }

    8.分组

     1     //8.分组
 2     @Test
 3     public void test8(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         criteria.setProjection(Projections.projectionList().add(Projections.rowCount()).add(Projections.groupProperty("teacher.id")));
 6         List<Object[]> list = criteria.list();
 7         for (Object[] objects : list) {
 8             for (Object object : objects) {
 9                 System.out.println(object);
10             }
11         }
12     }

     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

     1     //9.通过老师id查询学生(使用别名查询)
 2     @Test
 3     public void test9(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         criteria.add(Restrictions.eq("teacher.tid", 1));
 6         List<Student> list = criteria.list();
 7         for (Student student : list) {
 8             System.out.println(student.getName()+student.getTeacher().getTid());
 9         }
10         System.out.println("=============以下是通过别名查询================");
11         Criteria criteria2 = session.createCriteria(Student.class);
12         criteria2.createAlias("teacher", "t");
13         criteria2.add(Restrictions.eq("t.id", 1));
14         List<Student> list2 = criteria2.list();
15         for (Student student : list2) {
16             System.out.println(student.getName()+student.getTeacher().getTid());
17         }
18     }
    1 //setFetchMode: 抓取延迟的属性
2         Criteria criteria3 = session.createCriteria(Student.class);
3         criteria3.setFetchMode("teacher", FetchMode.JOIN);
4         List<Student> list3 = criteria3.list();
5         /*for (Student student : list3) {
6             System.out.println(student.getName()+student.getTeacher().getTid());
7         }*/

     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)

     1     //10.离线查询
 2     @Test
 3     public void test10(){
 4         DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Student.class);
 5         Criteria criteria = detachedCriteria.getExecutableCriteria(session);
 6         List<Student> list = criteria.list();
 7         for (Student student : list) {
 8             System.out.println(student.getId()+student.getName());
 9         }
10     }

    11.子查询

     1     //11.子查询
 2     @Test
 3     public void test11(){
 4         Criteria criteria = session.createCriteria(Student.class);
 5         criteria.add(Restrictions.in("id", new Object[]{1,2,3}));
 6         List<Student> list = criteria.list();
 7         for (Student student : list) {
 8             System.out.println(student.getId()+student.getName());
 9         }
10         System.out.println("==================================");
11         //离线查询作为子查询的一部分
12         DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Student.class);
13         detachedCriteria.setProjection(Projections.property("id"));
14         detachedCriteria.add(Restrictions.between("id", 60, 90));
15         Criteria criteria2 = session.createCriteria(Student.class);
16         criteria2.add(Property.forName("id").in(detachedCriteria));
17         List<Student> list2 = criteria2.list();
18         for (Student student : list2) {
19             System.out.println(student.getId()+student.getName());
20         }
21     }
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  • 原文地址：https://www.cnblogs.com/57rongjielong/p/8305840.html
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