ManyToMany :Constraint exception

[karshak]

Hello All ,
   I am creating a simple many to many relation ship example , but i am getting this contraint exception:

Here is my code:

package org.domain.bannerStore.entity;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;


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

    private static final long serialVersionUID = 1L;
   
    private Long id;
   
    private String name;

    private Set<Course> courses = new HashSet<Course>(0);


    @ManyToMany(cascade=CascadeType.ALL)
    @JoinTable(name = "student_course",
                joinColumns = {@JoinColumn(name = "student_id", nullable=false, insertable=false)},
                inverseJoinColumns={@JoinColumn(name="course_id", nullable=false, insertable=false)}  
    )
    public Set<Course> getCourses(){
      return courses;
    }
   
    public void setCourses(Set<Course> courses){
      this.courses = courses;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "id")
    public Long getId() {return id;}

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

    @Column(name = "name")
    public String getName() {
      return name;
    }
    public void setName(String s){
      name=s;
    }
  }
   
//////////////////////////Course Class;
package org.domain.bannerStore.entity;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;


@Entity
@Table(name = "course")
public class Course implements java.io.Serializable {

    private static final long serialVersionUID = 1L;
   
    private Long id;
   
    private String name;
   
    private Set<Student> students = new HashSet<Student>(0);
   

    @ManyToMany(cascade=CascadeType.ALL)   
    @JoinTable(name = "student_course",
                joinColumns = {@JoinColumn(name = "course_id", nullable=false, insertable=false)},
                inverseJoinColumns={@JoinColumn(name="student_id", nullable=false, insertable=false)}  
    )
    public Set<Student> getStudents(){
      return students;
    }
   
    public void setStudents(Set<Student> lefties){
      this.students = lefties;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "id")
    public Long getId() {return id;}

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

    @Column(name = "name")
    public String getName() {
      return name;
    }
    public void setName(String s){
      name=s;
    }

  }
   
/////////////Test method
        @Override
        public String persist() {
                        Student student = new Student();
                        student.setName("Jason");
                       
                        Course course = new Course();
                        course.setName("J2EE");
                       
                        course.getStudents().add(student);
                       
                        return super.persist();
       }



I Am doing it right and do i need to mention the join table class too, Any one implemented Many to Many relationship's ?

[jmchiaradia]

Hi,
try this:

In Student class:

@ManyToMany
public Set<Course> getCourses(){
      return courses;
}
public void setCourses(Set<Course> courses){
      this.courses = courses;
}

in Course class:

@ManyToMany(mappedBy="courses")
public Set<Student> getStudents(){
      return students;
}
public void setStudents(Set<Student> lefties){
      this.students = lefties;
}