Question 172771 in Mysql Question posted in
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How come Spring Boot app creates only “User” table when I have “User” class and two classes “Student” and “Teacher” that inherit from it?

I’am using jakarta and when I run the app the "Student" and "Teacher" tables didn’t created and only the "User" table is created. What could be the problem ?

User class

import jakarta.persistence.*;

import java.io.Serializable;

@Entity
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;
    private String first_name;
    private String last_name;


    public User(String first_name, String last_name) {
        this.first_name = first_name;
        this.last_name = last_name;
    }

    public User() {}
}

Student class

import com.fasterxml.jackson.annotation.JsonManagedReference;
import jakarta.persistence.*;

import java.io.Serializable;
import java.util.Set;


@Entity
public class Student extends User implements Serializable {

    @Id
    @GeneratedValue(strategy = jakarta.persistence.GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;

    private String first_name;
    private String last_name;

    @JsonManagedReference
    @ManyToMany(mappedBy = "students")
    private Set<Module> modules;

    private double moyenneGenerale;


    public Student(String first_name, String last_name) {
        super(first_name, last_name);
    }

    public Student() {
    }
}

Module class:

import jakarta.persistence.*;

import java.io.Serializable;
import java.util.Set;

@Entity
public class Module implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;

    @OneToMany
    private Set<Subject> subjects;

    @ManyToMany
    private Set<Student> students;


    public Module(Set<Subject> subjects) {

    }

    public Module() {}


    public Long getId() {
        return id;
    }

    public Set<Subject> getSubjects() {
        return subjects;
    }

    public void setSubjects(Set<Subject> subjects) {
        this.subjects = subjects;
    }

    public void calculMoyenne() {

    }
}

Subject class:

import jakarta.persistence.*;

@Entity
public class Subject {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;
    private String name;
    private int coefficient;

    @ManyToOne
    @JoinColumn(name = "module_id")
    private Module module;


    public Subject(String name, int coefficient, Module module) {
        this.name = name;
        this.coefficient = coefficient;
        this.module = module;
    }

    public Subject() {}


    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getCoefficient() {
        return coefficient;
    }

    public void setCoefficient(int coefficient) {
        this.coefficient = coefficient;
    }

}

ERROR 7576 — [ main] j.LocalContainerEntityManagerFactoryBean : Failed to initialize JPA
EntityManagerFactory: Collection
‘com.example.grademanagement_hamzarami.models.Student.modules’ is
‘mappedBy’ a property named ‘student’ which does not exist in the
target entity ‘com.example.grademanagement_hamzarami.models.Module’

Error creating bean with name ‘entityManagerFactory’ defined in class
path resource
[org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]:
Collection
‘com.example.grademanagement_hamzarami.models.Student.modules’ is
‘mappedBy’ a property named ‘student’ which does not exist in the
target entity ‘com.example.grademanagement_hamzarami.models.Module’

Tags:

2

Answers


  1. 0

    Your Module @Entity lacks a student field so your module table lacks this column.

    However, I suspect that your have a model problem.

    The relationship between Student and Module is ManyToMany (aka associative), ie a Student can enrole in many Modules and a Module can be presented to many Students.

    This almost the same model if you substitute Course of Module.

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  2. 0

    Modify Student entity like this:

    @JsonManagedReference
@ManyToMany(mappedBy = "students")
private List<Module> modules;

    And also you should use Set instead of List for all the relations.

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