Question

I’m trying to fix a problem with my hibernate db system, but I’m not sure about what should I doing wrong:

I have two entities: vertex (Vertice) and Tag. One vertice should have many tags. When I add a vertex with Tags in a Set inside, the vertexes are saved into DB, the tags also, but the column FK for vertex is recorded as null. This means that I’m not able to retrieve the set of tags when I need. Thanks for helping!

Beneath are the codes:

import java.util.Set;
public class Vertice {

private long id;
private Set<Tag> tags;
private String amostra = new String();
private String chave = new String();

public Vertice() {
}

public long getId() {
    return id;
}
public void setId(long id) {
    this.id = id;
}
public Set<Tag> getTags() {
    return tags;
}
public void setTags(Set<Tag> tags) {
    this.tags = tags;
}
public String getAmostra() {
    return amostra;
}
public void setAmostra(String amostra) {
    this.amostra = amostra;
}
public String getChave() {
    return chave;
}
public void setChave(String chave) {
    this.chave = this.geraChave(chave);
}

private String geraChave(String chave){
    String _chave = new String();
    _chave = chave;
    try{
        if(this.getTags()!=null){
            for(Tag t: this.getTags()){
                _chave = _chave + t.getTexto();
            }
        }
    }
    catch(Exception e){
        e.printStackTrace();
    }
    return _chave;
}

}

Class Tag:

public class Tag {
    private long id;
    private int linha;
    private int coluna;
    private String texto = new String();

private Vertice vertice;

public Vertice getVertice() {
    return vertice;
}
public void setVertice(Vertice vertice) {
    this.vertice = vertice;
}
public int getLinha() {
    return linha;
}
public int getColuna() {
    return coluna;
}
public void setColuna(int coluna) {
    this.coluna = coluna;
}
public void setLinha(int linha) {
    this.linha = linha;
}
public String getTexto() {
    return texto;
}
public void setTexto(String texto) {
    this.texto = texto;
}
public long getId() {
    return id;
}
public void setId(long id) {
    this.id = id;
}

}

Piece of code of VerticeDAO Class:

public boolean salvaAtualiza(Vertice VerticeArg) throws ViolacaoChaveUnicaException{

boolean ret = false;

try{
     if(VerticeArg.equals(null)){
        throw new Exception("O objeto <Vertice> foi informado vazio.");
     }
     else{
        sess.beginTransaction();
        sess.saveOrUpdate(VerticeArg);
        ret = true;
     }
    }
    catch(ConstraintViolationException e){
        throw new ViolacaoChaveUnicaException(
           "Houve uma violação de chave na tentativa " + 
              "de gravar os dados no BD");
    }
    catch(Exception e){
        e.printStackTrace();
    }
    return ret;
}

XML of Vertex Entity (Vertice.hbm.xml):

<hibernate-mapping>
<class name="xx.xxx.xxx.Vertice" table="pcommjava_vertice">
    <id name="id" column="vertice_id" type="long">
        <generator class="native" />
    </id>
    <property name="amostra">
        <column name="vertice_amostra" not-null="true" length="1920"/>
    </property>
    <property name="chave">
        <column name="vertice_chave" not-null="true" length="50" unique="true" unique-key="vertice_chave"/>
    </property>
    </class>

Tag XML mapping (Tag.hbm.xml):

<hibernate-mapping>
<class name="xx.xxx.xxx.Tag" table="pcommjava_tag">
    <id name="id" column="tag_id" type="long">
        <generator class="native" />
    </id>
    <property name="linha">
        <column name="tag_linha" not-null="true" />
    </property>
    <property name="coluna">
        <column name="tag_coluna" not-null="true" />
    </property>
    <property name="texto">
        <column name="tag_texto" not-null="true" />
    </property>

    <many-to-one name="vertice" cascade="all" not-null="true" column="tag_vertice" class="xx.xxx.xxx.Vertice" />

</class>

Finally, the hibernate.cfg.xml:

 <hibernate-configuration>
 <session-factory>
  <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
  <property name="hibernate.connection.password">SOMEPASSWORD</property>
  <property name="hibernate.connection.url">jdbc:mysql://00.00.000.000:3306/DB2</property>
  <property name="hibernate.connection.username">developer</property>
  <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
  <property name="hibernate.current_session_context_class">thread</property>
  <property name="hibernate.show_sql">true</property>
  <property name="hibernate.format_sql">true</property>
  <!-- Automatic schema creation (begin) === -->
  <property name="hibernate.hbm2ddl.auto">create</property>
  <!-- Simple memory-only cache -->
  <property name="hibernate.cache.provider_class">org.hibernate.cache.HashtableCacheProvider</property>

  <mapping class="xx.xx.xxx.Vertice"
   package="xx.xx.xxx.Vertice" resource="xx/xxx/xxx/Vertice.hbm.xml"/>
  <mapping class="xx.xx.xxx.Tag"
   package="xx.xx.xxx.Tag" resource="xx/xx/xxx/Tag.hbm.xml"/>

 </session-factory>

</hibernate-configuration>

Answer 1

The problem is you haven’t defined set<Tag> in vertex.hbm.xml. According to my understanding, when you put Set in Vertice.java, it becomes either one-to-many or many-to-many relationship. In addition to this, if you put Vertice reference in Tag.java it becomes bi-directional relationship.
For more info see this:

http://docs.jboss.org/hibernate/orm/3.3/reference/en/html/collections.html