Taking the same Employee and Employee Details example of the above question.
Employee.javapackage com.test.onetoone.mappingimport javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.GeneratedValue;import static javax.persistence.GenerationType.IDENTITY;import javax.persistence.Id;import javax.persistence.OneToOne;import javax.persistence.Table; @Entity@Table(name = "emp") public class Employee implements java.io.Serializable{   private Integer empId;   private EmployeeDetail empDetail;    public Employee(){}   @Id   @GeneratedValue(strategy = IDENTITY)   @Column(name = "EMP_ID", unique = true, nullable = false)   public Integer getEmpId()   {       return this.empId;   }   public void setEmpId(Integer empId)   {       this.empId = empId;   }   @OneToOne(fetch = FetchType.LAZY, mappedBy = "emp", cascade = CascadeType.ALL)   public EmployeeDetail getEmpDetail()    {       return this.empDetail;   }    public void setEmpDetail(EmployeeDetail empDetail)    {       this.empDetail = empDetail;    } }
File: EmployeeDetail.java
package com.test.onetoone.mappingimport javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.OneToOne;import javax.persistence.PrimaryKeyJoinColumn;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.TemporalType;import org.hibernate.annotations.GenericGenerator;import org.hibernate.annotations.Parameter; @Entity@Table(name = "emp_detail")public class EmployeeDetail implements java.io.Serializable {    private Integer empId;   private Employee emp;   private String name;   private String address;    public EmployeeDetail() {}    public EmployeeDetail(Employee emp, String name, String address)    {       this.emp = emp;       this.name = name;       this.address = address;   }    @GenericGenerator(name = "generator", strategy = "foreign",    parameters = @Parameter(name = "property", value = "emp"))   @Id   @GeneratedValue(generator = "generator")   @Column(name = "EMP_ID", unique = true, nullable = false)   public Integer getEmpId()    {       return this.empId;   }    public void setEmpId(Integer empId)    {       this.empId = empId;   }    @OneToOne(fetch = FetchType.LAZY)   @PrimaryKeyJoinColumn   public Employee getEmp()    {       return this.emp;    }   public void setEmp(Employee emp)    {       this.emp = emp;   }    @Column(name = "ADDRESS", nullable = false, length = 400)   public String getAddress()    {       return this.address;   }    public void setAddress(String address)    {       this.address = address;   }    @Column(name = "EMP_NAME", nullable = false)   public String getName()    {       return this.name;   }    public void setName(String name)    {       this.name = name;   } }3. Hibernate Configuration File- Puts annotated classes Employee.java and EmployeeDetail.java in your Hibernate configuration file, and also MySQL connection details.File : hibernate.cfg.xmlcom.mysql.jdbc.Driverjdbc:mysql://localhost:3306/mytestdbrootpasswordorg.hibernate.dialect.MySQLDialecttrue   _{Your Comment}