parent-child relationship within the same class

jesion · **Joined:** Thu Sep 18, 2003 3:34 am **Posts:** 9

Hi,

I've problems with defining parent-child type relationship regarding objects of the same class. I got error: "Schema text failed: duplicate import: ProductGroup" when generating db schema. What's wrong? Could someone post sample definition that must work?

wojtek

christian · **Posted:** Thu Sep 18, 2003 4:56 pm

This is a parent/child bidirectional relationship for nested Groups:

Code:

    <class name="test.Group"
           table="GROUP">

        <id name="OID"
            column="GROUP_ID"
            type="string"
            unsaved-value="null"
            length="32">
            <generator class="uuid.hex"/>
        </id>

        <property name="name" column="GROUP_NAME" not-null="true"/>

        <many-to-one name="parentGroup"
                     class="test.Group"
                     column="PARENT_GROUP_ID"
                     cascade="none"
                     not-null="false"/>

        <set name="childGroups"
               table="GROUP"
               cascade="all"
               inverse="true">
            <key column="PARENT_GROUP_ID"/>
            <one-to-many class="test.GROUP"/>
        </set>

    </class>

bruce1 · **Joined:** Thu Sep 18, 2003 10:52 am **Posts:** 4

christian,

hello, I tried your codes thousands of time. But it could not work.
The follows are the java codes generated by
net.sf.hibernate.tool.hbm2java.CodeGenerator

Code:

package airline.hibernate;

import java.io.Serializable;
import java.util.Set;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;

/** @author Hibernate CodeGenerator */
public class Group implements Serializable {

    /** identifier field */
    private String id;

    /** nullable persistent field */
    private String myname;

    /** nullable persistent field */
    private airline.hibernate.Group parentGroup;

    /** persistent field */
    private Set childGroups;

    /** full constructor */
    public Group(java.lang.String myname, airline.hibernate.Group parentGroup, Set childGroups) {
        this.myname = myname;
        this.parentGroup = parentGroup;
        this.childGroups = childGroups;
    }

    /** default constructor */
    public Group() {
    }

    /** minimal constructor */
    public Group(Set childGroups) {
        this.childGroups = childGroups;
    }

    public java.lang.String getId() {
        return this.id;
    }

    public void setId(java.lang.String id) {
        this.id = id;
    }

    public java.lang.String getMyname() {
        return this.myname;
    }

    public void setMyname(java.lang.String myname) {
        this.myname = myname;
    }

    public airline.hibernate.Group getParentGroup() {
        return this.parentGroup;
    }

    public void setParentGroup(airline.hibernate.Group parentGroup) {
        this.parentGroup = parentGroup;
    }

    public java.util.Set getChildGroups() {
        return this.childGroups;
    }

    public void setChildGroups(java.util.Set childGroups) {
        this.childGroups = childGroups;
    }

    public String toString() {
        return new ToStringBuilder(this)
            .append("id", getId())
            .toString();
    }

    public boolean equals(Object other) {
        if ( !(other instanceof Group) ) return false;
        Group castOther = (Group) other;
        return new EqualsBuilder()
            .append(this.getId(), castOther.getId())
            .isEquals();
    }

    public int hashCode() {
        return new HashCodeBuilder()
            .append(getId())
            .toHashCode();
    }

}

I got the error like

NoClassFoundError:airline/hibernate/Group (wrong name: airline/hibernate/Group)
at java.lang. Classloader.defineClass0(native method)

This error is not the "common class not fond error",
I deleted many-to-one and set tag in hbm.xml. It Works!!!!

Can you tell me why?

bruce1 · **Joined:** Thu Sep 18, 2003 10:52 am **Posts:** 4

I got the answer, the error is

<one-to-many class="test.GROUP"/>

it should be <one-to-many class="test.Group"/>

christian · **Posted:** Fri Sep 19, 2003 5:13 am

Sorry, I only wrote that example down without testing. Thats why I'm usually writing my Hibernate mappings in IntelliJ IDEA. The editor not only automatically completes the XML, but also the class names :)