在一对多双向关联时，在一的一方需要设置@OneToMany和mappedby，在多的一方需要设置@ManyToOne和@JoinColumn
多对多：在多对多双向关联时，在控制的一方设置@ManyToMany和mappedby，在另一方需要设置@ManyToMany和@JoinTable
Demo目录 数据表 核心代码 application.properties #自己的数据库，hibernate可以创建表，但不能创库spring.datasource.url=jdbc:mysql://localhost:3306/hibernate?&characterEncoding=utf8spring.datasource.driver-class-name=com.mysql.jdbc.Driverspring.datasource.username=rootspring.datasource.password=password#create 删表后再创表，要丢数据，update 只能增加表或字段。我事先是没有数据表，只建了对象spring.jpa.hibernate.ddl-auto=create#是否在控制台上输出SQL语句spring.jpa.show-sql=true Student.java @Entitypublic class Student { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "student_id") private int id; @Column(name = "student_name") private String name; @Column(name = "student_password") private String password; @ManyToOne(cascade = CascadeType.ALL) @JoinColumn(name = "school") private School school; @ManyToMany(cascade = CascadeType.ALL,mappedBy = "students")//mappedBy=“关联属性名” private Set teachers; public Student() { } public Student(String name, String password, School school, Set teachers) { this.name = name; this.password = password; this.school = school; this.teachers = teachers; } //Get and Set...} Teacher.java @Entity@Table(name = "teacher")public class Teacher { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "teacher_id") private int id; @Column(name = "teacher_name") private String name; @Column(name = "teacher_password") private String password; @ManyToOne(cascade = CascadeType.ALL) @JoinColumn(name = "school") private School school; @ManyToMany(cascade = CascadeType.ALL) @JoinTable(name = "teacher_student",//中间表名 joinColumns = {@JoinColumn(name = "teacherid")},//当前对象id在中间表的列名 inverseJoinColumns = {@JoinColumn(name = "studentid")}//另一张表在中间表的列名 ) private Set students; public Teacher() { } public Teacher(String name, String password, School school, Set students) { this.name = name; this.password = password; this.school = school; this.students = students; } //Get and Set...} School.java @Entitypublic class School { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "school_id") private int id; @Column(name = "school_name") private String name; @OneToMany(cascade = CascadeType.ALL,mappedBy = "school") private Set students; @OneToMany(cascade = CascadeType.ALL,mappedBy = "school") private Set teachers; public School() { } public School(String name, Set students, Set teachers) { this.name = name; this.students = students; this.teachers = teachers; } //Get and Set... 运行结果POST之后
