Encountered with JPA ManytoMany Relationship Build time errors with IntelliJ IDEA - spring-boot

Question

I'm very new to this topic so i followed a tutorial. after following steps i got some build time errors.
I have imported javax persistence like this.
import javax.persistence.*;
Then the student model class
#Entity
#Table(name="STUDENT")
public class Student {
#Id
#GeneratedValue
private Integer studentId;
#ManyToOne(cascade = CascadeType.ALL)
#JoinTable(name="Enrollment", joinColumns = {#JoinColumns(name="student_id")},
inverseJoinColumns = {#JoinColumns(name="course_id")})
private List<Course> courses = new ArrayList<>();
}
The Course model class.
#Entity
#Table(name="COURSE")
public class Course {
#GeneratedValue
private Integer id;
#ManyToMany(mappedBy ="courses")
private List<Student> students = new ArrayList<>();
These are set of errors that i have got
incompatible types: javax.persistence.JoinColumns cannot be converted to javax.persistence.JoinColumn
cannot find symbol
symbol: method name()
location: #interface javax.persistence.JoinColumns
annotation #javax.persistence.JoinColumns is missing a default value for the element 'value'
Can anyone help me to get rid of this issues?
Thanks.

Answer 1

A #JoinTable annotation really has a joinColumns parameter, but the syntax you had used is not correct. If tables are joined by only column and inverse column you shouldn't use a #JoinColumns annotation. You have to change it in the following way:
#Entity
#Table(name="STUDENT")
public class Student {
#Id
#GeneratedValue
private Integer studentId;
#ManyToOne(cascade = CascadeType.ALL)
#JoinTable(
name="Enrollment",
joinColumns = #JoinColumn(name="student_id", referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name="course_id", referencedColumnName = "id"))
private List<Course> courses = new ArrayList<>();
}
and only if joining goes by more then one column you have to do something like this:
#Entity
#Table(name="STUDENT")
public class Student {
#Id
#GeneratedValue
private Integer studentId;
#ManyToOne(cascade = CascadeType.ALL)
#JoinTable(
name="Enrollment",
joinColumns = #JoinColumns{
#JoinColumn(name="student_id", referencedColumnName = "id"),
#JoinColumn(name="another_id", referencedColumnName = "another_id")
},
inverseJoinColumns = #JoinColumn(name="course_id", referencedColumnName = "id"))
private List<Course> courses = new ArrayList<>();
}
Hope it will help