Max Foxell wrote:
>
> Jeff,
>
> we have the same problem with Enum classes. In the database we are
> storing a single selection of an enumeration as a string but in Java
> we want the String to be retrieved from the database as an instance of
> our Enum class. e.g.
>
> In database we store the string "RED", but we want to map that to the
> "RED" instance of the following enum class (i.e. map to
> ColoursEnum.RED):
>
> public class ColoursEnum
> {
> private String name;
> private Colours(String name) { this.name = name; }
> public String toString() { return name; }
> public static final ColoursEnum RED = new ColoursEnum("RED");
> public static final ColoursEnum GREEN = new ColoursEnum("GREEN");
> public static final ColoursEnum BLUE = new ColoursEnum("BLUE");
> }
>
> Castor can already perform mappings between simple database types to
> classes (where the database types indicate the identity of an object).
> It would be great to hook into this mechanism using the mapping file
> (e.g. identify a "converter" class that implements a particular
> interface to perform the conversion from/to database type to/from Java
> class). A mechanism like this could significantly improve Castor's
> mapping strengths (and reduce the impedance mismatch further). I'm
> sure converters of this sort could be put to all sorts of good uses.
> Maybe one of the Castor developers (Thomas?) could indicate whether
> this functionality is on their "to do" list or even in the next
> release ;-)?
>
This should now work in the CVS (at least it does for Castor XML). I
have added the ever powerful handler attribute to the field element of a
mapping file. This enables you to implement your own FieldHandler and
use it instead of the automatically created one from Castor.
I recommend using type="string" as follows in this simple example
--- Mapping File ---
<?xml version="1.0"?>
<mapping>
<class name="my.package.Foo">
<field name="color" type="string"
handler="my.package.ColorHandler"/>
</class>
</mapping>
--- Special FieldHandler ---
package my.package;
import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.ValidityException;
/**
* The FieldHandler for the "color" field of the Foo class.
**/
public class ColorHandler
implements org.exolab.castor.mapping.FieldHandler
{
/**
* Creates a new ColorHandler for the Foo class
**/
public ColorHandler() {
super();
}
/**
* Returns the value of the field from the object.
*
* @param object The object
* @return 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
*/
public Object getValue( Object object )
throws IllegalStateException
{
Color color = ((Foo)object).getColor();
if (color == null) return null;
return color.toString();
}
/**
* Sets the value of the field on the object.
*
* @param object The object
* @param 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
* @thorws IllegalArgumentException The value passed is not of
* a supported type
*/
public void setValue( Object object, Object value )
throws IllegalStateException, IllegalArgumentException
{
Color color = Color.valueOf((String)value);
((Foo)object).setColor(color);
}
/**
* Sets the value of the field to a default value.
* <p>
* Reference fields are set to null, primitive fields are set to
* their default value, collection fields are emptied of all
* elements.
*
* @param 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
*/
public void resetValue( Object object )
throws IllegalStateException, IllegalArgumentException
{
((Foo)object).setColor((Color)null);
}
/**
* @deprecated No longer supported
*/
public void checkValidity( Object object )
throws ValidityException, IllegalStateException
{
//-- add validation check if desired
}
/**
* Creates a new instance of the object described by this field.
*
* @param parent The object for which the field is created
* @return A new instance of the field's value
* @throws IllegalStateException This field is a simple type and
* cannot be instantiated
*/
public Object newInstance( Object parent )
throws IllegalStateException
{
//-- Since it's marked as a string...just return null,
//-- it's not needed.
return null;
}
}
--- Foo.java ---
package my.package;
public class Foo {
private Color _color = null;
public Foo() {
super();
}
public Color getColor() {
return _color;
}
public void setColor(Color color) {
_color = color;
}
}
--- Color.java ---
/*
* This class was automatically generated with
* <a href="http://castor.exolab.org";>Castor 0.9.3</a>, using an
* XML Schema.
* $Id$
*/
package my.package;
//---------------------------------/
//- Imported classes and packages -/
//---------------------------------/
import java.io.Serializable;
import java.util.Enumeration;
import java.util.Hashtable;
import org.exolab.castor.xml.*;
/**
*
* @version $Revision$ $Date$
**/
public class Color implements java.io.Serializable {
//--------------------------/
//- Class/Member Variables -/
//--------------------------/
/**
* The red type
**/
public static final int RED_TYPE = 0;
/**
* The instance of the red type
**/
public static final Color RED = new Color(RED_TYPE, "red");
/**
* The green type
**/
public static final int GREEN_TYPE = 1;
/**
* The instance of the green type
**/
public static final Color GREEN = new Color(GREEN_TYPE, "green");
/**
* The blue type
**/
public static final int BLUE_TYPE = 2;
/**
* The instance of the blue type
**/
public static final Color BLUE = new Color(BLUE_TYPE, "blue");
private static java.util.Hashtable _memberTable = init();
private int type = -1;
private java.lang.String stringValue = null;
//----------------/
//- Constructors -/
//----------------/
private Color(int type, java.lang.String value) {
super();
this.type = type;
this.stringValue = value;
} //-- test.types.Color(int, java.lang.String)
//-----------/
//- Methods -/
//-----------/
/**
* Returns an enumeration of all possible instances of Color
**/
public static java.util.Enumeration enumerate()
{
return _memberTable.elements();
} //-- java.util.Enumeration enumerate()
/**
* Returns the type of this Color
**/
public int getType()
{
return this.type;
} //-- int getType()
/**
**/
private static java.util.Hashtable init()
{
Hashtable members = new Hashtable();
members.put("red", RED);
members.put("green", GREEN);
members.put("blue", BLUE);
return members;
} //-- java.util.Hashtable init()
/**
* Returns the String representation of this Color
**/
public java.lang.String toString()
{
return this.stringValue;
} //-- java.lang.String toString()
/**
* Returns a new Color based on the given String value.
* @param string
**/
public static Color valueOf(java.lang.String string)
{
Object obj = null;
if (string != null) obj = _memberTable.get(string);
if (obj == null) {
String err = "'" + string + "' is not a valid Color";
throw new IllegalArgumentException(err);
}
return (Color) obj;
} //-- test.types.Color valueOf(java.lang.String)
}
---------
Hope that solves the problem for you...
--Keith
>
> Jeff Hoare wrote:
>
> > Hi,
> > Is there anyway to map user defined data types in Castor. We are
> > using a guio
> > framwork that defines its own set of java types. In may cases these
> > are just
> > wrappers for some base Java Class, for example TextString is a
> > wrapper for a
> > String, and the "name" property returns one of these classes.
> > We don't want to have to store these seperatly in tables, but as
> > column
> > attributes of the class itself.
> > I can add specific getters/setters on the actual classes that return
> > standard
> > java representations, but it would be good not to have to have these
> > xtra's.
> > So :-)
> > Is it possible to map such classes to standard castor
> > representations
> > or
> > Does this require an extension of the castor framework?
> >
> > Jeff
> >
> > -----------------------------------------------------------
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> > [EMAIL PROTECTED] with a subject of:
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