[Java Spring Data] @JoinTable, @JoinColumn, joinColumns and inverseJoinColumns

@OneToMany: One Student To Many Courses.

@JoinTable(name = "Enrollment"): Join Enrollment table.

joinColumns: with use "student_id" to link Student and enrollment tables.

inverseJoinColumns: Here the source table become "Enrollment", not "Stduent" anymore. Target table become "Course" table. 

CascadeType.ALL is that the persistence will propagate (cascade) all EntityManager operations (PERSIST, REMOVE, REFRESH, MERGE, DETACH) to the relating entities. Which means if we delete a student, will also delete the Enrollemnt data from Enrollment table.

FetchType.EAGER: Which means when loading a student related data, it will also load course data which related to that student.

For example;

In Course table:

　　A column "department":

@ManyToOne
@JoinColumn(name="course_dept_id")
private Department department;

In Department table:

　　@OneToMany(mappedBy="department")