This is a javabean class with a one-to-many relationship. Note that there is a School parameter in the Student class. Normally, when we write javabeans, we only write a set collection on the School side. Student writes a School, it is really possible to directly find a student's school?
Does that mean that if we write normal javabeans, we can only add data to the foreign key in the database, and cannot realize the realization of finding a student's school?
So if hibernate is written like this, is it not possible to achieve it?
Secondly, why can we add foreign keys to the student table in the database when we use school.getAllStudent().add(new student());?
1 import java.util.* ;
2 public class TestDemo{ // Set the relationship between school and students
3 public static void main(String args[]){
4 School sch = new School("Tsinghua University") ; // Instantiate School object
5 Student s1 = new Student("Zhang San",21) ; // Instantiate student object
6 Student s2 = new Student("Li Si",22 ) ;
7 Student s3 = new Student("Wang Wu", 23 ) ;
8 sch.getAllStudents().add(s1) ;// Add student
9 to school sch.getAllStudents().add(s2) ;
10 sch.getAllStudents().add(s3) ;
11 s1.setSchool(sch) ; // A student belongs to a school
12 s2.setSchool (sch) ;
13 s3.setSchool(sch) ;
14 System.out.println(sch) ;
15 Iterator<Student> iter = sch.getAllStudents().iterator() ;
16 while (iter.hasNext()){
17 System.out.println("\t|- " + iter.next()) ;
18 }
19 }
20 }
21
22 //Student class
23 class Student{
24 private String name ;
25 private int age ;
26 private School school; // A student belongs to a school
27 public Student(String name, int age){
28 this .setName(name) ;
29 this . setAge(age) ;
30 }
31 public void setSchool(School school){
32 this .school = school ;
33 }
34 public School getSchool(){
35 return this.school ;
36 }
37 public void setName(String name){
38 this.name = name ;
39 }
40 public void setAge(int age){
41 this.age = age ;
42 }
43 public String getName(){
44 return this.name;
45 }
46 public int getAge(){
47 return this.age ;
48 }
49 public String toString(){
50 return "Student name: " + this .name + "; age: " + this .age ;
51 }
52 }
53
54 // School class
55 class School{
56 private String name ;
57 private List<Student> allStudents ; // One school has multiple students
58 public School(String name){
59 this .allStudents = new ArrayList<Student> ();
60 this .setName(name) ;
61 }
62 public void setName(String name){
63 this .name = name ;
64 }
65 public String getName(){
66 return this .name;
67 }
68 public List<Student> getAllStudents(){ // Get all students
69 return this .allStudents ;
70 }
71 public String toString(){
72 return "School name:" + this .name ;
73 }
74 }
代码参考：https://www.cnblogs.com/xscn/archive/2013/08/09/3249274.html