NullpointerException in one-to-many

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

Someone asked it before but didn't receive an answer:

I try to configure a one-to-many relation but when the hibernate session start-up and arrive to map my parent class the log give me a NullPointerException... why?

It says: org.xml.sax.SAXParseException: Element "set" does not allow "one-to-many" here.

This causes problems:

Code:

/**
 * @hibernate.set
 * @hibernate.collection-one-to-many
 *  class="base.domainobjects.Address"
 * 
 * @return
 */
public Set getAdresses() {
   return adresses;
}

As you see I started using XDoclet. When I start the task topdown.hbm2ddl, I receive a NullpointerException when the build script is trying to export the schema. I modified the Workshop example which I downloaded from this site.

gavin · **Posted:** Sat Nov 15, 2003 6:10 am

Looks like you are missing an @hibernate.collection-key mapping

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

That was fast!

I think I found the reason.

hibernate.cfg.xml

Code:

    <session-factory>
        <property name="connection.url">jdbc:mysql://localhost:3306/liberty</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>
        <property name="show_sql">true</property>
        <property name="dialect">net.sf.hibernate.dialect.MySQLDialect</property>

        <mapping resource="base/domainobjects/Address.hbm.xml"/>
        <mapping resource="base/domainobjects/Person.hbm.xml"/>
    </session-factory>

In the section mapping resource there were some other classes from which I have removed the tag @hibernate.class. It seems I must delete them in this xml file too.

If I still have problems with it, I come back here.

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

Now it seems to work. But something is very strange. I have to use set instead of list in the XDoclet tag! If I use list as XDoclet tag, then it says: org.xml.sax.SAXParseException: Element "list" does not allow "one-to-many" here.

And the generated SQL script contains no foreign keys. Why not?

Is there a task to automatically update the schema in the database? What I get is a SQL script which I have to execute manually.

Here is the latest code snippet:

Code:

/**
    * @hibernate.set
    *  inverse="true"
    *  lazy="true"
    *  cascade="all"
    * @hibernate.collection-key
    *  column="personId"
    * @hibernate.collection-one-to-many
    *  class="base.domainobjects.Address"
    * @return
    */
public List getAdresses() {
   return adresses;
}

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

The missing foreign key was because of inverse = true.

emmanuel · **Posted:** Sat Nov 15, 2003 7:11 am

List is an indexed collection, you need to have

Code:

@hibernate.collection-index ...

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

epbernard wrote:

List is an indexed collection, you need to have

Code:

@hibernate.collection-index ...

If I do this, no foreign key is generated. If I use XDoclet tag "set", a foreign key is generated.

The Java type must be list. How do I map it correctly?

emmanuel · **Posted:** Sat Nov 15, 2003 7:39 am

Probably something like that

Code:

/**
    * @hibernate.list
    *  lazy="true"
    *  cascade="all"
    * @hibernate.collection-key
    *  column="personIndex"
    * @hibernate.collection-index
    *  column="personId"
    * @hibernate.collection-one-to-many
    *  class="base.domainobjects.Address"
    * @return
    */
public List getAdresses() {
   return adresses;
}

If you inverse="true", you must have a many-to-one from the Address object to Person

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

Okay, that worked.

Now I need to map a byte array.

This didn't work:

Code:

/**
 * @hibernate.primitive-array 
 * @return
 */
public byte[] getEncryptedString() {
   return encryptedString;
}

It says: org.xml.sax.SAXParseException: Element "primitive-array" requires additional elements.

Whats wrong?

emmanuel · **Posted:** Mon Nov 17, 2003 4:14 am

Well, I think there is a need for a goods fully documented and googleizable tutorial ;-)

Well, I don't use xdoclet myself but I would say that a primitive array is basicaly a indexed collection so you need @hibernate.collection-key and @hibernate.collection-index tags plus a @hibernate.collection-element one.

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

I was wrong. It works with @hibernate.primitive-array.

quereinsteiger · **Joined:** Sat Oct 11, 2003 11:13 am **Posts:** 69

quereinsteiger wrote:

I was wrong. It works with @hibernate.primitive-array.

It SEEMED to work. What solved my problem is:

Code:

/**
 * TODO
 * @hibernate.property
 *  type="binary"
 */
public byte[] getEncryptedPassword() {
   return encryptedPassword;
}

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