Mapping Bean Fields

The bean-descriptor maps a bean attribute into one JCR node (or a set of properties). Generally, this attribute is an object based on a custom class.

Based on our model defined here, the following bean-descriptor is used to map the bean field “pageInfo” (PageInfo class) into the JCR node called “pageInfo”.

The PageInfo class has a corresponding class-descriptor in the mapping file. By this way, the Persistence Manager can map each PageInfo attributes. It is not necessary to specify the type in the bean-descriptor. The Persistence Manager uses the Java
introspection to get information on the each bean fields.

The JCR Structure

Following our example, the resulting JCR structure is:

/mysite/page1
  /mysite/page1/pageInfo
       my:title = "This is my page title"
       my:description = "This is my page description"
  ... other subnodes for page1 ...

By default, the persistence manager will create a subnode
(/mysite/page1/pageInfo) for the bean-descriptor pageInfo.

Using Another Bean Converter

The OCM framework gives you the freedom to choose another kind of mapping for bean fields. For example, you can use a custom bean converter to access to the parent node (see the next
section below).

This can be done by writing your own bean converter class and reference this class in the bean-descriptor.

Predefined Bean Converters

Here is the list of existing custom bean converters:

Custom Bean Converter Class	Description
org.apache.jackrabbit.ocm.persistence.beanconverter.impl.ParentBeanConverterImpl	Map a bean field to the parent node. it is used to access to the parent object in read-only mode. See below the example based on a Folder object.
org.apache.jackrabbit.ocm.persistence.beanconverter.impl.InlineBeanConverterImpl	Bean converter used to map some node properties into one nested bean field. The corresponding bean field is not associated to a subnode.

If you want to use one of this bean converter, you have to
reference it into a bean-field descriptor.

The following descriptor bean-descriptor contains a reference to
its parent folder (parentFolder attribute). Now the CmsObjectImpl
object has an attribute (parentFolder) that contains a reference
to the parent node.

<class-descriptor 
    className="org.apache.jackrabbit.ocm.testmodel.inheritance.impl.CmsObjectImpl" 
    jcrType="my:cmsobjectimpl" >
  <field-descriptor fieldName="path" path="true" />
  <field-descriptor fieldName="name" jcrName="my:name" id="true" />
  <bean-descriptor 
    fieldName="parentFolder" 
    converter="org.apache.jackrabbit.ocm.persistence.beanconverter.impl.ParentBeanConverterImpl" 
  />
</class-descriptor>

Building your own Bean Converters

Here is the different steps used to create a new bean converter :

First, specify the converter class in the bean descriptor:

<class-descriptor 
    className="org.apache.jackrabbit.ocm.testmodel.inheritance.impl.CmsObjectImpl" 
    jcrType="my:cmsobjectimpl" >
  <bean-descriptor 
    fieldName="parentFolder" 
    converter="org.apache.jackrabbit.ocm.persistence.beanconverter.impl.ParentBeanConverterImpl" 
  />
</class-descriptor>

Then, implement the converter class (based on the interface
org.apache.jackrabbit.ocm.persistence.beanconverter.BeanConverter).

Your bean converter class can also extends the class
AbstractBeanConverterImpl to have a default implementation for some methods.

import javax.jcr.Node;
import javax.jcr.Session;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.jackrabbit.ocm.exception.JcrMappingException;
import org.apache.jackrabbit.ocm.exception.PersistenceException;
import org.apache.jackrabbit.ocm.exception.RepositoryException;
import org.apache.jackrabbit.ocm.mapper.Mapper;
import org.apache.jackrabbit.ocm.mapper.model.BeanDescriptor;
import org.apache.jackrabbit.ocm.mapper.model.ClassDescriptor;
import org.apache.jackrabbit.ocm.persistence.atomictypeconverter.AtomicTypeConverterProvider;
import org.apache.jackrabbit.ocm.persistence.beanconverter.BeanConverter;
import org.apache.jackrabbit.ocm.persistence.objectconverter.ObjectConverter;
/**
 *
 * Bean converter used to access to the parent object.
 *
 *
 * @author <a href="mailto:christophe.lombart@gmail.com">Lombart Christophe </a>
 *
 */
public class ParentBeanConverterImpl extends AbstractBeanConverterImpl implements BeanConverter {

  private final static Log log = LogFactory.getLog(ParentBeanConverterImpl.class);

  public ParentBeanConverterImpl(Mapper mapper, ObjectConverter objectConverter, AtomicTypeConverterProvider atomicTypeConverterProvider)
  {
    super(mapper, objectConverter, atomicTypeConverterProvider);
  }

  public void insert(Session session, Node parentNode, BeanDescriptor beanDescriptor, ClassDescriptor beanClassDescriptor, Object object, ClassDescriptor parentClassDescriptor, Object parent)
      throws PersistenceException, RepositoryException, JcrMappingException {

      // Add code to insert the object
  }

  public void update(Session session, Node parentNode, BeanDescriptor beanDescriptor, ClassDescriptor beanClassDescriptor, Object object, ClassDescriptor parentClassDescriptor, Object parent)
      throws PersistenceException, RepositoryException, JcrMappingException {

      // Add code to update the object
  }

  public Object getObject(Session session, Node parentNode, BeanDescriptor beanDescriptor, ClassDescriptor beanClassDescriptor, Class beanClass, Object parent)
      throws PersistenceException, RepositoryException,JcrMappingException {

      // Add code to retrieve the object
  }

  public void remove(Session session, Node parentNode, BeanDescriptor beanDescriptor, ClassDescriptor beanClassDescriptor, Object object, ClassDescriptor parentClassDescriptor, Object parent)
	    throws PersistenceException,  RepositoryException, JcrMappingException {

      // Add the code to remove the object
  }

}