Update using one to one relationship hibernate

Question

I have one parent object as Employee and child object as Address. I just need to update the both objects using Employee object. But when updating using employee object i just getting emp_id should not be null. Here is my table and entity

CREATE TABLE `employee` (
`employee_id` bigint(20) NOT NULL AUTO_INCREMENT,
`employee_name` varchar(30) NOT NULL,
`employee_desg` varchar(30) NOT NULL,
`salary` varchar(30) NOT NULL,
`employee_reference_id` varchar(10) NOT NULL,
PRIMARY KEY (`employee_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

Address table

CREATE TABLE `address` (
`address_id` bigint(20) NOT NULL AUTO_INCREMENT,
`emp_id` bigint(20) NOT NULL,
`address` varchar(255) NOT NULL,
PRIMARY KEY (`address_id`),
KEY `employee_address` (`emp_id`),
CONSTRAINT `employee_address` FOREIGN KEY (`emp_id`) REFERENCES `employee`   (`employee_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

Employee Object

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

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

@Id
@GeneratedValue
@Column(name = "EMPLOYEE_ID")
private int id;

@Column(name = "EMPLOYEE_NAME")
private String employeeName;

@Column(name = "EMPLOYEE_DESG")
private String employeeDesg;

@Column(name = "SALARY")
private String salary;

@Column(name = "EMPLOYEE_REFERENCE_ID")
private String employeeReferenceId;

public String getEmployeeReferenceId() {
    return employeeReferenceId;
}

public void setEmployeeReferenceId(String employeeReferenceId) {
    this.employeeReferenceId = employeeReferenceId;
}

@OneToOne(mappedBy="employee", cascade = CascadeType.ALL)
private Address address;


public String getEmployeeName() {
    return employeeName;
}

public void setEmployeeName(String employeeName) {
    this.employeeName = employeeName;
}

public String getEmployeeDesg() {
    return employeeDesg;
}

public void setEmployeeDesg(String employeeDesg) {
    this.employeeDesg = employeeDesg;
}

public String getSalary() {
    return salary;
}

public void setSalary(String salary) {
    this.salary = salary;
}

public Address getAddress() {
    return address;
}

public void setAddress(Address address) {
    this.address = address;
}

public int getId() {
    return id;
}

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

}

Address Object

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;



@Entity
@Table(name = "ADDRESS")
public class Address {

@Id
@Column(name="ADDRESS_ID")
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;

@Column(name = "ADDRESS")
private String address;
@OneToOne(fetch=FetchType.EAGER , cascade=CascadeType.ALL, orphanRemoval=true)
@JoinColumn(name="emp_id",referencedColumnName="employee_id")
private Employee employee;

public String getAddress() {
    return address;
}

public void setAddress(String address) {
    this.address = address;
}

public Employee getEmployee() {
    return employee;
}

public void setEmployee(Employee employee) {
    this.employee = employee;
}

public Address() {

}

public int getId() {
    return id;
}

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

My code is

public class StudentUtil1To1 {
public static void main(String args[]){
    SessionFactory factory=null;
    Configuration configuration=null;
    ServiceRegistry registry=null;
    Session session=null;
    try{
        configuration= new Configuration();
        configuration.configure();
        registry=new StandardServiceRegistryBuilder().configure().applySettings(configuration.getProperties()).build();
        factory=configuration.configure("hibernate.cfg.xml").buildSessionFactory(registry);
        session= factory.openSession();
        session.beginTransaction();


            Employee emp=new Employee();
            emp.setId(1);
            emp.setEmployeeReferenceId("CP001");
            emp.setEmployeeName("Muthu");
            emp.setEmployeeDesg("Developer");
            emp.setSalary("15000");

            Address address=new Address();
            address.setAddress("3, Civil aerodrome, CBE");


            emp.setAddress(address);
            address.setEmployee(emp);
            session.update(emp);



        System.out.println("Successfuly Saved");
        session.getTransaction().commit();

    }catch(Exception e){
        e.printStackTrace();
    }finally{
        if(session!=null){
            session.close();
        }
        if(factory!=null){
            factory.close();
        }
    }
}
}

And the error is

09:40:48.815 [http-nio-8081-exec-7] WARN  o.h.e.jdbc.spi.SqlExceptionHelper - SQL Error: 1048, SQLState: 23000
09:40:48.816 [http-nio-8081-exec-7] ERROR o.h.e.jdbc.spi.SqlExceptionHelper - Column 'emp_id' cannot be null

What i need to for update. Correct my mistake.

Answer 1

Since you have already mapped Address entity in employee entity like this

@OneToOne(mappedBy="employee", cascade = CascadeType.ALL)
private Address address;

You dont have to do same thing in address class means

@OneToOne(fetch=FetchType.EAGER , cascade=CascadeType.ALL, orphanRemoval=true)
@JoinColumn(name="emp_id",referencedColumnName="employee_id")
private Employee employee;

Above code is not required in address entity.And remove the employee attribute from address class. Now you already added the CascadeType.ALL in OneToOne annotation and save only employee object like this

 Employee emp=new Employee();
            Address address=new Address("your address");
            emp.setAddress(address);
            emp.setId(1);
            emp.setEmployeeReferenceId("CP001");
            emp.setEmployeeName("Muthu");
            emp.setEmployeeDesg("Developer");
            emp.setSalary("15000");
            session.update(emp);

Answer 2

1.@MapppedBy annotation means：the entity annotationed by @MapppedBy,give up the reference of key，so in the employee table,dont have the column named "address_id". the relation between Employee and Address controlled by "address" table. 2. when you use [session.update(emp);],you havent have the data of "Employee" table.but emp_id is the FOREIGN KEY,so will occur this problem 3. i can first insert Employee，then [session.update(emp);]