How to handle Many-To-Many Relation with existed data in Hibernate

Question

I had three table ie,personalinfo,groups_designation,groups_desig_category

• personalinfo:pid(personal id)
• groups_designation:gid(group id)
• groups_desig_category:gid,pid

Actually I have data in both table's (personalinfo,groups_designation).So we have provide one screen.In that,The user selects the group and assign personal id and the data pulled into groups_desig_category table.In this scenario,i mapped like

Personal.hbm.xml:-

<set name="empwthgrp" inverse="true" lazy="true"  table="groups_desig_category">
 <key>
    <column name="pid" not-null="true" />
  </key>

            <many-to-many entity-name="com.aims.beans.DesignationGroupBean">
                <column name="gid" not-null="true" />
            </many-to-many>

</set>

Personal.java:-

/**
 * 
 */
private static final long serialVersionUID = 1L;
private int pid,deptno;
private String name,designation;
private Address address;
private Address permentaddress;
private Set famildtlslst;
private Set empwthgrp=new HashSet();
public Set getEmpwthgrp() {
    return empwthgrp;
}
public void setEmpwthgrp(Set empwthgrp) {
    this.empwthgrp = empwthgrp;
}
public Set getFamildtlslst() {
    return famildtlslst;
}
public void setFamildtlslst(Set famildtlslst) {
    this.famildtlslst = famildtlslst;
}
public Address getPermentaddress() {

    return permentaddress;
}
public void setPermentaddress(Address permentaddress) {

    this.permentaddress = permentaddress;
}
public Address getAddress() {

    return address;
}
public void setAddress(Address address) {
    this.address = address;
}
public int getDeptno() {
    return deptno;
}
public void setDeptno(int deptno) {
    this.deptno = deptno;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public int getPid() {
    return pid;
}
public void setPid(int pid) {
    this.pid = pid;
}
public String getDesignation() {
    return designation;
}
public void setDesignation(String designation) {
    this.designation = designation;
}

GroupingDesig.hbm.xml:-

<class name="beans.DesignationGroupBean" table="groups_designation" proxy=beans.DesignationGroupBean">

<id name="gid" column="gid" type="java.lang.Integer">
 <generator class="sequence"><param name="sequence">gid_seq</param> </generator>
</id>
<property name="gname"  type="java.lang.String" column="gname" not-null="true" />
<property name="description"  type="java.lang.String" column="description" not-null="true" />
<set name="grpwthemp" inverse="true" lazy="true" table="groups_desig_category">
 <key>
    <column name="gid" not-null="true" />
  </key>
             <many-to-many entity-name="com.aims.beans.Personal">
                <column name="pid" not-null="true" />
            </many-to-many>
</set>
</class>

DesignationGroupBean.java:-

private int gid;
private String gname,description;
private Set grpwthemp=new HashSet();
public Set getGrpwthemp() {
    return grpwthemp;
}
public void setGrpwthemp(Set grpwthemp) {
    this.grpwthemp = grpwthemp;
}
public String getDescription() {
    return description;
}
public void setDescription(String description) {
    this.description = description;
}
public int getGid() {
    return gid;
}
public void setGid(int gid) {
    this.gid = gid;
}
public String getGname() {
    return gname;
}
public void setGname(String gname) {
    this.gname = gname;
}

Actually I trying session.saveOrUpdate(pBean).But its not working.May be can change one-to many and many-to-one instead of many-to-many relation.I think it is not suitable in this scenario.So,How to handle in this scenario?.If you using reverse engineering then it created as one-to-many and many-to-one relation? why?.Please help me.

Update:-

I am implemented in one-to-many and many-to-one relation hibernate whereas in database its many-to-many relation.then Its working fine and below pasted the hibernate mapping files with one-to-many relation ship

GroupingDesig.hbm.xml:-

<set name="grpwthemp" inverse="true" lazy="true" table="groups_desig_category">
 <key>
    <column name="gid" not-null="true" />
  </key>
                <one-to-many class="com.aims.beans.GroupAssignment"/>


           <!--  <many-to-many entity-name="com.aims.beans.Personal">
                <column name="pid" not-null="true" />
            </many-to-many>-->

</set>

Personal.hbm.xml

<set name="empwthgrp" inverse="true" lazy="true"  table="groups_desig_category">
 <key>
    <column name="pid" not-null="true" />
  </key>
    <one-to-many class="com.aims.beans.GroupAssignment"/>

            <!--
            <many-to-many entity-name="com.aims.beans.DesignationGroupBean">
                <column name="gid" not-null="true" />
            </many-to-many>-->

</set>

AssigGroupingDesig.hbm.xml:-

<many-to-one name="personal" column="pid" class="com.aims.beans.Personal" not-null="true"></many-to-one>
<many-to-one name="desigdt" column="gid" class="com.aims.beans.DesignationGroupBean" not-null="true"></many-to-one>

When will be came picture the relation ship?.I have search many-to-many relation example's in web ie,.

Mykong many-to-many

Please help me. My Question is when will be came/used many-to-many relation ship in real time?.

Update 2:-

Thanks.Removing the inverse tag its working fine.But i have doubt regarding generation of deleting the query.Please check the logs

 /* load com.beans.Personal */ select personal0_.pid as pid0_, personal0_.name as name5_0_, personal0_.DEPTNO as DEPTNO5_0_, personal0_.designation as designat4_5_0_, personal0_.pddress1 as pddress5_5_0_, personal0_.pddress2 as pddress6_5_0_, personal0_.pcity as pcity5_0_, personal0_.pstate as pstate5_0_, personal0_1_.HomeAddress1 as HomeAddr2_7_0_, personal0_1_.HomeAddress2 as HomeAddr3_7_0_, personal0_1_.homecity as homecity7_0_, personal0_1_.homestate as homestate7_0_ from personalinfo personal0_, address personal0_1_ where personal0_.pid=personal0_1_.pid and personal0_.pid=?



delete collection com.beans.Personal.empwthgrp */ delete from groups_desig_category where pid=?




insert collection row com.beans.Personal.empwthgrp */ insert into groups_desig_category (pid, gid) values (?, ?)

why generating the "delete from groups_desig_category where pid=?".Plz help me

Update 3:-

Yes.Iam loading the data using session.get.becuase i got exception regarding the some of mandatory fields.that is reason i loaded the data then update the records

          per=(Personal)session.get(Personal.class,new Integer(pBean.getPid()));
    per.setEmpwthgrp(pBean.getEmpwthgrp());
    session.saveOrUpdate(per);

Answer 1

In your many-to-many mappings, you set both of them to inverse . You need to choose one entity that will own the relationship - for that one, in the mapping, you will remove the inverse="true" setting. That will be the entity that, when saved or updated, will persist the person to group relationship.

Since in your question you posted saveOrUpdate(pBean) , and I assume pBean is Personal entity, then you need to remove the inverse="true" setting in Personal.hbm.xml .

More info in the reference documentation: http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/associations.html#assoc-bidirectional-join-m2m