Hibernate Bidirectional Mapping short note

Here is my Hibernate/JPA bidirectional mapping short note.

One To One







Student StudentRegistration
@Id
@Column(name="student_id")
private Long studentId;
@Id
@Column(name="registration_no")
private Long registrationNo;
@Column(name="student_name")
private String name;
@Column(name="level")
private String level;
@Column(name="registration_date")
@Temporal(TemporalType.DATE)
private Date regDate;
@OneToOne
StudentRegistration studentRegistration;
@OneToOne(mappedBy="studentRegistration")
Student student;

Student is the owner, We add owner side property name to 'mappedBy'  of other side.

Database tables created by Hibernate

student
student_id student_name STUDENTRGISTRATION_registration_no

student_registration
registration_no level registration_date

If you want to change STUDENTRGISTRATION_registration_no column name to stu_reg_no add @JoinColumn annotation.

@OneToOne
@JoinColumn(name="stu_reg_no")
StudentRegistration studentRegistration;

  View Sample Code

One to Many/ Many to One 


Employee Department
@Id
@Column(name="emp_id")
private Long id;
@Id
@Column(name="dep_id")
private Long id;
@Column(name="emp_name")
private String name;
@Column(name="dep_name")
private String name;
@ManyToOne
Department department;
@OneToMany(mappedBy="department")
List<Employee> emps;


Database tables created by Hibernate

employee
emp_id emp_name DEPARTMENT_dep_id

department
dep_id dep_name

  View Sample Code

Many to Many








Employee Project
@Id
@Column(name="emp_id")
private Long id;
@Id
@Column(name="project_id")
private Long id;
@Column(name="emp_name")
private String name;
@Column(name="project_name")
private String name;
@ManyToMany(mappedBy="employees")
List<Project> projects;
@ManyToMany
List<Employee> employees;


Database tables created by Hibernate

employee
emp_id emp_name

project
project_id project_name

project_employee
projects_project_id employees_emp_id

If you want to change project_employee table name to pro_emp add @JoinTable annotaion
    @ManyToMany
    @JoinTable(name="pro_emp")
    List<Employee> employees;

  View Sample Code

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