Spring And Hibernate MVC - spring-mvc

Question

Hey guys i have stuck in the hibernate Relation with spring MVC , I have class like Student and this class is having the OneToOne relation with the Parent class ,My Error is When i tried to delete Student Object the parent Object Doesn't allow to delete the Student Object
It is giving an error like
Hibernate: delete from Student where id=?
WARN : org.hibernate.engine.jdbc.spi.SqlExceptionHelper - SQL Error: 1451, SQLState: 23000
ERROR: org.hibernate.engine.jdbc.spi.SqlExceptionHelper - Cannot delete or update a parent row: a foreign key constraint fails (`digischool`.`parent`, CONSTRAINT `FK_l65r4icaxmteeq1tg96t6n3ol` FOREIGN KEY (`student_id`) REFERENCES `student` (`id`))
"
i have Student Model Class like
#Entity
public class Student implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private long id;
private String name;
private Parent parent;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
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;
}
#OneToOne(mappedBy="student",fetch=FetchType.EAGER)
public Parent getParent() {
return parent;
}
public void setParent(Parent parent) {
this.parent = parent;
}
}
Parent model class like
#Entity
public class Parent {
private long id;
private String name;
private String phoneNumber;
private String email;
private String relation;
private Student student;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
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 String getPhoneNumber() {
return phoneNumber;
}
public void setPhoneNumber(String phoneNumber) {
this.phoneNumber = phoneNumber;
}
#OneToOne(fetch=FetchType.EAGER)
#JoinColumn(name="student_id")
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
public String getRelation() {
return relation;
}
public void setRelation(String relation) {
this.relation = relation;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
In order to delete Student Object i have written DAO like
public boolean deleteStudent(long studentId) {
if(studentId > 0){
Session session = getSessionFactory().getCurrentSession();
Query query = session.createQuery("DELETE FROM Student S WHERE S.id = :studentId");
query.setParameter("studentId", studentId);
int rowChanged = query.executeUpdate();
if(rowChanged > 0){
return true;
}
}
return false;
}
My db is looks like
Please help me out i am new bee to this Spring World

Answer 1

This is because you are forgeting to remove the relationship from the parent entity prior to deleting the student.
the way to do this:
public boolean deleteStudent(long studentId) {
if(studentId > 0){
// get parent object
parent.setStudent(null); // THIS REMOVES THE RELATIONSHIP FROM PARENT CLASS SINCE ITS STORED THERE
// save parent object with emptied student field
Session session = getSessionFactory().getCurrentSession();
Query query = session.createQuery("DELETE FROM Student S WHERE S.id = :studentId");
query.setParameter("studentId", studentId);
int rowChanged = query.executeUpdate();
if(rowChanged > 0){
return true;
}
}
return false;
}
FYI
use the hibernates own functions when you can.
check out this link for some ways to delete a object http://www.codejava.net/frameworks/hibernate/hibernate-basics-3-ways-to-delete-an-entity-from-the-datastore

Answer 2

You can use attribute orphanRemoval = true with annotation #OneToOne with your Parent entity
#OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY, orphanRemoval = true)
public Student getStudent() {
return student;
}
....
hope it help.