关于一对多，多对多的多表查询的控制

* 1.一对多

* sql:select c.*,s.* from classes c,student s where c.cid=s.cid;

* hql:from Classes c,Student s where c.cid=s.classes.cid，注意与上句的区别；

* 得到的list是object[]，数组中的元素是Classes和Student对象；

*

*/

@Test

public void testOneToMany_EQ(){

Session   session = sessionFactory.openSession();

Query query = session.createQuery( "from Classes c,Student s where c.cid=s.classes.cid");

List list = query.list();

System. out.println(query.list().size());

session.close();

}

/**

* 2.带属性的查询；

* list中装的是object[];

*/

@Test

public void testOneToMany_EQ_Property(){

Session   session = sessionFactory.openSession();

Query query = session.createQuery( "select c.cname,s.sname from Classes c,Student s where c.cid=s.classes.cid");

query.list();

session.close();

}

/**

* 3.带属性查询，将查询结果封装成一个bean；

* 得到的list中装的是classView对象；

*/

@Test

public void testOneToMany_EQ_Property_Constructor(){

Session   session = sessionFactory.openSession();

Query query = session.createQuery( "select new cn.itheima03.hibernate.domain.ClassesView(c.cname,s.sname) " +

"from Classes c,Student s where c.cid=s.classes.cid");

List list = query.list();

session.close();

}

/**

* 4.内连接

* 结果与例子1一样；

*/

@Test

public void testOneToMany_InnerJoin_Query(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Classes c inner join c.students s");

Query query = session.createQuery(buffer.toString());

query.list();

session.close();

}

/**

* 5.迫切内连接1：获取所有有学生的班级及班级下的学生；

* 要想得到的集合中装的Classes对象，对象中set集合中装student，可以使用迫切内链接。

*

*/

@Test

public void testOneToMany_InnerJoin_Fetch_Query_1(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Classes c inner join fetch c.students s");

Query query = session.createQuery(buffer.toString());

List list = query.list();

session.close();

}

/**

* 6.迫切内连接2

* 从学生端出发；

*/

@Test

public void testOneToMany_InnerJoin_Fetch_Query_2(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Student s inner join fetch s.classes c");

Query query = session.createQuery(buffer.toString());

query.list();

session.close();

}

/**

* 7.迫切内连接3：获取属性，封装结果；

* select new cn.itheima03.hibernate.domain.ClassView(c.cname,s.sname)

*   from Student s inner join fetch s.classes c；

* 上述的 hql语句会报错，因为from后面想要的结构和select想要的结构是冲突的，所以

如果在from后面加fetch,不能写select语句，如果加select，不能写fetch,两者只能选择其一

*

*/

@Test

public void testOneToMany_InnerJoin_Fetch_Query_Property(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

//下面的写法不对；

//        buffer.append("select new cn.itheima03.hibernate.domain.ClassView(c.cname,s.sname) " +

//                 " from Student s inner join fetch s.classes c");

//不要fetch;

buffer.append( "select new cn.itheima03.hibernate.domain.ClassesView(c.cname,s.sname)  " +

"  from Student s inner join  s.classes c " );

Query query = session.createQuery(buffer.toString());

List list = query.list();

session.close();

}

/**

* 8.迫切左外连接

* 从班级出发，得到班级对应的学生

*/

@Test

public void testOneToMany_LeftJoin_Fetch(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Classes c left outer join fetch c.students s");

Query query = session.createQuery(buffer.toString());

List<Classes> list = query.list();

for (Classes classes : list) {

System. out.println("classes:" +classes.getCname());

Set<Student> students = classes.getStudents();

for (Student student : students) {

System. out.println("     student:" +student.getSname());

}

}

session.close();

}

/**

* 9.迫切左外连接2

* 从学生出发，得到对应的班级

*/

@Test

public void testOneToMany_RightJoin_Fetch(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Student s left outer join fetch s.classes ");

Query query = session.createQuery(buffer.toString());

List<Student> list = query.list();

for (Student student : list) {

System. out.println("student:" +student.getSname());

if (student.getClasses()!=null) {

System. out.println("     " +student.getClasses().getCname());

}

}

session.close();

}

* 1.得到所有的学生以及其对应的课程

* 从学生端出发

* list装的是学生；

*/

@Test

public void testManyToMany_LeftJoin_Fecth(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Student s left outer join fetch s.courses");

Query query = session.createQuery(buffer.toString());

List list = query.list();

session.close();

}

/**

* 2.得到所有的课程及课程下对应的学生；

* list装的是课程

*/

@Test

public void testManyToMany_LeftJoin_Fecth_2(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Course c left outer join fetch c.students s");

Query query = session.createQuery(buffer.toString());

query.list();

session.close();

}

/**

* 3.一对多和多对多的结合

* 得到所有班级下的所有学生以及所有学生下的所有课程；

* 从班级出发

*/

@Test

public void testManyToManyAndOneToMany(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Classes c left outer join fetch" +

" c.students s left outer join fetch s.courses");

Query query = session.createQuery(buffer.toString());

List<Classes> classeList = query.list();

//去掉集合中的重复元素

Set<Classes> sets = new HashSet<Classes>(classeList);

classeList = new ArrayList<Classes>(sets);

System. out.println(classeList.size());

for(Classes classes:classeList){//遍历班级

System. out.println(classes.getCname());

Set<Student> students = classes.getStudents();//得到班级下的学生

for(Student student:students){//遍历学生

System. out.println(student.getSname());

Set<Course> courses = student.getCourses();

for(Course course:courses){//遍历学生下的课程

System. out.println(course.getCname());

}

}

}

session.close();

}

/**

* 从中间表出发，班级有学生，学生修课程，故从学生角度出发进行查询；

*/

@Test

public void testManyToManyAndOneToMany_2(){

Session   session = sessionFactory.openSession();

StringBuffer buffer = new StringBuffer();

buffer.append( "from Student s left outer join fetch s.classes c

left outer join fetch s.courses cc");

Query query = session.createQuery(buffer.toString());

List<Student> studentList = query.list();

for(Student student:studentList){

System. out.println(student.getSname());

Classes classes = student.getClasses();

System. out.println(classes.getCname());

Set<Course> courses = student.getCourses();

for(Course course:courses){

System. out.println(course.getCname());

}

}

session.close();

}

/*******************************************************************************/

/**

* 面向对象的查询

*/

@Test

public void testQueryCriteria(){

Session   session = sessionFactory.openSession();

List<Classes>  classesList = session.createCriteria(Classes.class).list() ;

System. out.println(classesList.size());

session.close();

}

@Test

public void testQueryCriteria_Where(){

Session   session = sessionFactory.openSession();

Classes classes = (Classes)session.createCriteria(Classes.class).add(Restrictions.eq("cid" , 1L)).uniqueResult();

System. out.println(classes.getCname());

session.close();

}

}