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

Student.java

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1. package com.sameera.entity;  
2.   
3. import java.io.Serializable;  
4. import javax.persistence.*;  
5.   
6. @Entity  
7. @Table(name = "student")  
8. public class Student implements Serializable {  
9.   
10.     @Id  
11.     @Column(name = "student_id")  
12.     private Integer studentId;  
13.   
14.     @Column(name = "student_name")  
15.     private String name;  
16.   
17.     @OneToOne  
18.     //@JoinColumn(name="stu_reg_no")  
19.     private StudentRegistration studentRegistration;  
20.   
21.   
22.     public String getName() {  
23.         return name;  
24.     }  
25.   
26.     public void setName(String name) {  
27.         this.name = name;  
28.     }  
29.   
30.     public Integer getStudentId() {  
31.         return studentId;  
32.     }  
33.   
34.     public void setStudentId(Integer studentId) {  
35.         this.studentId = studentId;  
36.     }  
37.   
38.     public StudentRegistration getStudentRegistration() {  
39.         return studentRegistration;  
40.     }  
41.   
42.     public void setStudentRegistration(StudentRegistration studentRegistration) {  
43.         this.studentRegistration = studentRegistration;  
44.     }  
45. }  

package com.sameera.entity;

import java.io.Serializable;
import javax.persistence.*;

@Entity
@Table(name = "student")
public class Student implements Serializable {

    @Id
    @Column(name = "student_id")
    private Integer studentId;

    @Column(name = "student_name")
    private String name;

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


    public String getName() {
        return name;
    }

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

    public Integer getStudentId() {
        return studentId;
    }

    public void setStudentId(Integer studentId) {
        this.studentId = studentId;
    }

    public StudentRegistration getStudentRegistration() {
        return studentRegistration;
    }

    public void setStudentRegistration(StudentRegistration studentRegistration) {
        this.studentRegistration = studentRegistration;
    }
}

StudentRegistration.java

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1. package com.sameera.entity;  
2.   
3. import java.io.Serializable;  
4. import java.util.Date;  
5. import javax.persistence.*;  
6.   
7.   
8. @Entity  
9. @Table(name="student_registration")  
10. public class StudentRegistration implements Serializable {  
11.   
12.     @Id  
13.     @Column(name = "registration_no")  
14.     private Integer registrationNo;  
15.   
16.     @Column(name = "level")  
17.     private String level;  
18.   
19.     @Column(name = "registration_date")  
20.     @Temporal(TemporalType.DATE)  
21.     private Date registrationDate;  
22.       
23.     @OneToOne(mappedBy="studentRegistration")  
24.     private Student student;  
25.   
26.     public String getLevel() {  
27.         return level;  
28.     }  
29.   
30.     public void setLevel(String level) {  
31.         this.level = level;  
32.     }  
33.   
34.     public Date getRegistrationDate() {  
35.         return registrationDate;  
36.     }  
37.   
38.     public void setRegistrationDate(Date registrationDate) {  
39.         this.registrationDate = registrationDate;  
40.     }  
41.   
42.     public Integer getRegistrationNo() {  
43.         return registrationNo;  
44.     }  
45.   
46.     public void setRegistrationNo(Integer registrationNo) {  
47.         this.registrationNo = registrationNo;  
48.     }  
49.   
50.     public Student getStudent() {  
51.         return student;  
52.     }  
53.   
54.     public void setStudent(Student student) {  
55.         this.student = student;  
56.     }  
57.   
58.   
59. }  

package com.sameera.entity;

import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;


@Entity
@Table(name="student_registration")
public class StudentRegistration implements Serializable {

    @Id
    @Column(name = "registration_no")
    private Integer registrationNo;

    @Column(name = "level")
    private String level;

    @Column(name = "registration_date")
    @Temporal(TemporalType.DATE)
    private Date registrationDate;
    
    @OneToOne(mappedBy="studentRegistration")
    private Student student;

    public String getLevel() {
        return level;
    }

    public void setLevel(String level) {
        this.level = level;
    }

    public Date getRegistrationDate() {
        return registrationDate;
    }

    public void setRegistrationDate(Date registrationDate) {
        this.registrationDate = registrationDate;
    }

    public Integer getRegistrationNo() {
        return registrationNo;
    }

    public void setRegistrationNo(Integer registrationNo) {
        this.registrationNo = registrationNo;
    }

    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }


}

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

Employee.java

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1. package com.sameera.entity;  
2.   
3. import java.io.Serializable;  
4. import javax.persistence.*;  
5.   
6. @Entity  
7. @Table(name = "employee")  
8. public class Employee implements Serializable {  
9.   
10.     @Id  
11.     @Column(name = "emp_id")  
12.     private Long id;  
13.   
14.     @Column(name = "emp_name")  
15.     private String name;  
16.   
17.     @ManyToOne  
18.     private Department department;  
19.   
20.     public Department getDepartment() {  
21.         return department;  
22.     }  
23.   
24.     public void setDepartment(Department department) {  
25.         this.department = department;  
26.     }  
27.   
28.     public String getName() {  
29.         return name;  
30.     }  
31.   
32.     public void setName(String name) {  
33.         this.name = name;  
34.     }  
35.   
36.     public Long getId() {  
37.         return id;  
38.     }  
39.   
40.     public void setId(Long id) {  
41.         this.id = id;  
42.     }  
43.   
44.       
45. }  

package com.sameera.entity;

import java.io.Serializable;
import javax.persistence.*;

@Entity
@Table(name = "employee")
public class Employee implements Serializable {

    @Id
    @Column(name = "emp_id")
    private Long id;

    @Column(name = "emp_name")
    private String name;

    @ManyToOne
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public String getName() {
        return name;
    }

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

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    
}

Department.java

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1. package com.sameera.entity;  
2.   
3. import java.io.Serializable;  
4. import java.util.List;  
5. import javax.persistence.*;  
6.   
7. @Entity  
8. @Table(name="department")  
9. public class Department implements Serializable {  
10.   
11.     @Id  
12.     @Column(name = "dep_id")  
13.     private Long id;  
14.   
15.     @Column(name = "dep_name")  
16.     private String name;  
17.   
18.     @OneToMany(mappedBy = "department")  
19.     List<Employee> emps;  
20.   
21.     public List<Employee> getEmps() {  
22.         return emps;  
23.     }  
24.   
25.     public void setEmps(List<Employee> emps) {  
26.         this.emps = emps;  
27.     }  
28.   
29.     public Long getId() {  
30.         return id;  
31.     }  
32.   
33.     public void setId(Long id) {  
34.         this.id = id;  
35.     }  
36.   
37.     public String getName() {  
38.         return name;  
39.     }  
40.   
41.     public void setName(String name) {  
42.         this.name = name;  
43.     }  
44.       
45.   
46. }  

package com.sameera.entity;

import java.io.Serializable;
import java.util.List;
import javax.persistence.*;

@Entity
@Table(name="department")
public class Department implements Serializable {

    @Id
    @Column(name = "dep_id")
    private Long id;

    @Column(name = "dep_name")
    private String name;

    @OneToMany(mappedBy = "department")
    List<Employee> emps;

    public List<Employee> getEmps() {
        return emps;
    }

    public void setEmps(List<Employee> emps) {
        this.emps = emps;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

}

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

Employee.java

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1. package com.sameera.entity;  
2.   
3. import java.io.Serializable;  
4. import java.util.List;  
5. import javax.persistence.*;  
6.   
7. @Entity  
8. @Table(name = "employee")  
9. public class Employee implements Serializable {  
10.   
11.     @Id  
12.     @Column(name = "emp_id")  
13.     private Long id;  
14.   
15.     @Column(name = "emp_name")  
16.     private String name;  
17.       
18.     @ManyToMany(mappedBy = "employees")  
19.     private List<Project> projects;  
20.   
21.     public Long getId() {  
22.         return id;  
23.     }  
24.   
25.     public void setId(Long id) {  
26.         this.id = id;  
27.     }  
28.   
29.     public String getName() {  
30.         return name;  
31.     }  
32.   
33.     public void setName(String name) {  
34.         this.name = name;  
35.     }  
36.   
37.     public List<Project> getProjects() {  
38.         return projects;  
39.     }  
40.   
41.     public void setProjects(List<Project> projects) {  
42.         this.projects = projects;  
43.     }  
44. }  

package com.sameera.entity;

import java.io.Serializable;
import java.util.List;
import javax.persistence.*;

@Entity
@Table(name = "employee")
public class Employee implements Serializable {

    @Id
    @Column(name = "emp_id")
    private Long id;

    @Column(name = "emp_name")
    private String name;
    
    @ManyToMany(mappedBy = "employees")
    private List<Project> projects;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public List<Project> getProjects() {
        return projects;
    }

    public void setProjects(List<Project> projects) {
        this.projects = projects;
    }
}

Project.java

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1. package com.sameera.entity;  
2.   
3. import java.io.Serializable;  
4. import java.util.List;  
5. import javax.persistence.*;  
6.   
7. @Entity  
8. @Table(name = "project")  
9. public class Project implements Serializable {  
10.   
11.     @Id  
12.     @Column(name = "project_id")  
13.     private Long id;  
14.   
15.     @Column(name = "project_name")  
16.     private String name;  
17.       
18.     @ManyToMany  
19.     List<Employee> employees;  
20.   
21.     public List<Employee> getEmployees() {  
22.         return employees;  
23.     }  
24.   
25.     public void setEmployees(List<Employee> employees) {  
26.         this.employees = employees;  
27.     }  
28.   
29.     public Long getId() {  
30.         return id;  
31.     }  
32.   
33.     public void setId(Long id) {  
34.         this.id = id;  
35.     }  
36.   
37.     public String getName() {  
38.         return name;  
39.     }  
40.   
41.     public void setName(String name) {  
42.         this.name = name;  
43.     }  
44. }  

package com.sameera.entity;

import java.io.Serializable;
import java.util.List;
import javax.persistence.*;

@Entity
@Table(name = "project")
public class Project implements Serializable {

    @Id
    @Column(name = "project_id")
    private Long id;

    @Column(name = "project_name")
    private String name;
    
    @ManyToMany
    List<Employee> employees;

    public List<Employee> getEmployees() {
        return employees;
    }

    public void setEmployees(List<Employee> employees) {
        this.employees = employees;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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