org.exolab.castor.mapping
Class AbstractFieldHandler

java.lang.Object
  org.exolab.castor.mapping.loader.FieldHandlerFriend
      org.exolab.castor.mapping.ExtendedFieldHandler
          org.exolab.castor.mapping.AbstractFieldHandler

All Implemented Interfaces:

ConfigurableFieldHandler, FieldHandler

Direct Known Subclasses:

FieldHandlerImpl, GeneralizedFieldHandler, TransientFieldHandler, XMLFieldHandler

public abstract class AbstractFieldHandler
extends ExtendedFieldHandler
implements ConfigurableFieldHandler

An extended version of the FieldHandler interface which is used for adding additional functionality while preserving backward compatability.

Version:

$Revision: 8145 $ $Date: 2005-08-03 15:11:51 -0600 (Wed, 03 Aug 2005) $

Author:

Keith Visco

See Also:

FieldDescriptor, FieldHandler

Field Summary

protected Properties

_properties Configuration that can be used by subclasses when needed.

Constructor Summary

protected

AbstractFieldHandler() Creates a new default AbstractFieldHandler.

Method Summary

protected FieldDescriptor	getFieldDescriptor() Returns the FieldDescriptor for the field that this handler is reponsibile for, or null if no FieldDescriptor has been set.
abstract Object	getValue(Object object) Returns the value of the field from the object.
boolean	hasValue(Object object) Returns true if the "handled" field has a value within the given object.
abstract Object	newInstance(Object parent) Creates a new instance of the object described by this field.
abstract Object	newInstance(Object parent, Object[] args) Creates a new instance of the object described by this field.
abstract void	resetValue(Object object) Sets the value of the field to a default value.
void	setConfiguration(Properties config) Empty implementation of the ConfigurableFieldHandler interface, for convenience purpose.
void	setFieldDescriptor(FieldDescriptor fieldDesc) Sets the FieldDescriptor that this FieldHander is responsibile for.
abstract void	setValue(Object object, Object value) Sets the value of the field on the object.

Methods inherited from class org.exolab.castor.mapping.ExtendedFieldHandler

checkValidity

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.exolab.castor.mapping.FieldHandler

checkValidity

Field Detail

_properties

protected Properties _properties

Configuration that can be used by subclasses when needed.

Constructor Detail

AbstractFieldHandler

protected AbstractFieldHandler()

Creates a new default AbstractFieldHandler. This method should be called by all extending classes so that any important initialization code will be executed.

Method Detail

getFieldDescriptor

protected final FieldDescriptor getFieldDescriptor()

Returns the FieldDescriptor for the field that this handler is reponsibile for, or null if no FieldDescriptor has been set. This method is useful for implementations of the FieldHandler interface that wish to obtain information about the field in order to make the FieldHandler more generic and reusable, or simply for validation purposes.

Specified by:

getFieldDescriptor in class ExtendedFieldHandler

Returns:

the FieldDescriptor, or null if none exists.

setFieldDescriptor

public void setFieldDescriptor(FieldDescriptor fieldDesc)

Sets the FieldDescriptor that this FieldHander is responsibile for. By setting the FieldDescriptor, it allows the implementation of the FieldHandler methods to obtain information about the field itself. This allows a particular implementation to become more generic and reusable.

Specified by:

setFieldDescriptor in class ExtendedFieldHandler

Parameters:

fieldDesc - the FieldDescriptor to set

hasValue

public boolean hasValue(Object object)

Returns true if the "handled" field has a value within the given object.

By default this just checks for null. Normally this method is needed for checking if a value has been set via a call to the setValue method, or if the primitive value has been initialized by the JVM.

This method should be overloaded for improved value checking.

Returns:

true if the given object has a value for the handled field

getValue

public abstract Object getValue(Object object)
                         throws IllegalStateException

Returns the value of the field from the object.

Specified by:

getValue in interface FieldHandler

Specified by:

getValue in class ExtendedFieldHandler

Parameters:

object - The object

Returns:

The value of the field

Throws:

IllegalStateException - The Java object has changed and is no longer supported by this handler, or the handler is not compatiable with the Java object

newInstance

public abstract Object newInstance(Object parent)
                            throws IllegalStateException

Creates a new instance of the object described by this field.

Specified by:

newInstance in interface FieldHandler

Specified by:

newInstance in class ExtendedFieldHandler

Parameters:

parent - The object for which the field is created

Returns:

A new instance of the field's value

Throws:

IllegalStateException - This field is a simple type and cannot be instantiated

newInstance

public abstract Object newInstance(Object parent,
                                   Object[] args)
                            throws IllegalStateException

Creates a new instance of the object described by this field.

Specified by:

newInstance in class ExtendedFieldHandler

Parameters:

parent - The object for which the field is created

args - the set of constructor arguments

Returns:

A new instance of the field's value

Throws:

IllegalStateException - This field is a simple type and cannot be instantiated

resetValue

public abstract void resetValue(Object object)
                         throws IllegalStateException,
                                IllegalArgumentException

Sets the value of the field to a default value.

Reference fields are set to null, primitive fields are set to their default value, collection fields are emptied of all elements.

Specified by:

resetValue in interface FieldHandler

Specified by:

resetValue in class ExtendedFieldHandler

Parameters:

object - The object

Throws:

IllegalStateException - The Java object has changed and is no longer supported by this handler, or the handler is not compatiable with the Java object

IllegalArgumentException

setValue

public abstract void setValue(Object object,
                              Object value)
                       throws IllegalStateException,
                              IllegalArgumentException

Sets the value of the field on the object.

Specified by:

setValue in interface FieldHandler

Specified by:

setValue in class ExtendedFieldHandler

Parameters:

object - The object.

value - The new value.

Throws:

IllegalStateException - The Java object has changed and is no longer supported by this handler, or the handler is not compatiable with the Java object.

IllegalArgumentException - The value passed is not of a supported type.

setConfiguration

public void setConfiguration(Properties config)
                      throws ValidityException

Empty implementation of the ConfigurableFieldHandler interface, for convenience purpose. Subclasses that want to use any configuration should override this method.

Specified by:

setConfiguration in interface ConfigurableFieldHandler

Parameters:

config - the configuration data.

Throws:

ValidityException - if config is invalid for this FieldHandler.