一对多、多对一
Country类
@Entity
@Table(name = "Country")
public class Country {
@Id
//sequence identity
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer countryid;
private String country;
//mappedBy:指定由谁维护关联关系(设置的是关联对象的属性名)
@OneToMany(cascade = CascadeType.ALL,mappedBy = "country")
//@JoinColumn(name="countryid")
private List<City> citys=new ArrayList<>(); //关联属性
City类
@Entity
@Table(name = "City")
public class City {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer cityid;
private String cityname;
@ManyToOne(cascade = CascadeType.ALL)
private Country country;
CountryDao层
public interface CountryDao extends JpaRepository<Country,Integer>{
}CityDao层
public interface CityDao extends JpaRepository<City,Integer>{
}CountryController
@Controller
public class CountryController {
@Autowired
CountryDao dao;
@Autowired
CityDao dao1;
@Autowired
StudentDao dao2;
@Autowired
TeacherDao dao3;
//级联增加
@RequestMapping("/onetomany")
public String onetomany(){
Country c1=new Country();
c1.setCountry("中国万岁 ChinaNo.1");
City ct1=new City();
ct1.setCityname("中国香港");
City ct2=new City();
ct2.setCityname("中国台湾");
//维护国家与城市的一对多关系
c1.getCitys().add(ct1);
c1.getCitys().add(ct2);
dao.save(c1);
return "success";
}
//关联查询
@RequestMapping("/getcountry")
@ResponseBody
public Object get(){
return dao.findAll();
}
//级联删除
@RequestMapping("/deleteCountry")
public String delete(){
//检索国家实体
Country one = dao.getOne();
dao.delete(one);
return "success";
}
//由城市到国家的关联查询
@RequestMapping("/getCity")
@ResponseBody
public Object getCity(){
return dao1.findAll();
}
//添加学生和老师
@RequestMapping("/saveStudent")
public String save(){
Student student1=new Student("利亚东哥");
Student student2=new Student("玉姐");
Student student3=new Student("雄哥");
Teacher t1=new Teacher("山间的风");
student1.getTeachers().add(t1);
student2.getTeachers().add(t1);
student3.getTeachers().add(t1);
dao2.saveAll(Arrays.asList(student1,student2,student3));
return "success";
}
@RequestMapping("/saveTeacher")
public String saveTeacher(){
Teacher t1=new Teacher("帅的离谱");
List<Student> all = dao2.findAll();
t1.getStudents().addAll(all);
dao3.save(t1);
return "success";
}
@RequestMapping("/getTeacher")
@ResponseBody
public Object getTeacher(){
return dao3.getOne();
}
}
多对多
Teacher
@Entity
@Table(name="teacherinfo")
public class Teacher {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer teacherid;
private String teachername;
@ManyToMany(cascade = CascadeType.ALL)
//mappedby属性绝对不能再存在@JoinTable和@JoinColumn注解时使用
@JoinTable(name="student_teacher",joinColumns =@JoinColumn(name="teacherid") ,
inverseJoinColumns =@JoinColumn(name="studentid") )
private List<Student> students=new ArrayList<>();
Student
@Entity
@Table(name = "studentinfo")
public class Student {
@Id
@GeneratedValue
private Integer id;
private String name;
private Integer age;
private Integer sex;
@Column(name = "stu_name")
TeacherDao
public interface TeacherDao extends JpaRepository<Teacher,Integer> {
}StudentDao
public interface StudentDao extends JpaRepository<Student,Integer>{
}StudentController
@Controller
public class StudentController{
@Autowired
StudentDao studentDao;
@Autowired
TeacherDao teacherDao;
//添加学生和老师
@RequestMapping("/addstu")
@ResponseBody
public String addstu(){
Student student1=new Student("丽丽");
Student student2=new Student("明明");
Student student3=new Student("安安");
Teacher teacher1=new Teacher("筱丽");
student1.getTeachers().add(teacher1);
student2.getTeachers().add(teacher1);
student3.getTeachers().add(teacher1);
studentDao.saveAll(Arrays.asList(student1,student2,student3));
return "SUCCESS";
}
//多对多添加老师
@RequestMapping("/addDom")
@ResponseBody
public String addDom(){
Teacher teacher=new Teacher("李老师");
List<Student> all = studentDao.findAll();
teacher.getStudents().addAll(all);
teacherDao.save(teacher);
return "SUCCESS";
}
//多对多关联查询(慎用！！死循环！！)
@RequestMapping("/getDom")
@ResponseBody
public Object getDom(){
return teacherDao.getOne();
}
}