Has anyone written a user-defined Converter for the
org.apache.commons.beanutils package that works with
type-safe enumeration classes? It should be easy to
do, or even to write a converter generator.
Given
public class Suit {
private String name;
public final static Suit CLUBS = new Suit("Clubs");
public final static Suit DIAMONDS = new Suit("Diamonds");
public final static Suit HEARTS = new Suit("Hearts");
public final static Suit SPADES = new Suit("Spades");
private Suit(String name) {this.name = name;}
}
I can easily write a Converter that uses a Map from
String to Suit:
public class SuitConverter implements Converter {
private final static Map map = new HashMap();
static {
map.put(CLUBS.toString(), CLUBS);
map.put(DIAMONDS.toString(), DIAMONDS);
map.put(HEARTS.toString(), HEARTS);
map.put(SPADES.toString(), SPADES);
}
// Conversion methods follow.
}
It would be easier if I referred to the SuitConverter
inside Suit, but that would be poor engineering. I
would inflict the costs of having a SuitConverter on
all the clients, and many might not want to pay it.
However, I could use reflection to find all the
enumerants inside Suit, and create the map that way.
In pseudo-code, it would be:
public class SuitConverter implements Converter {
private final static Map map = new HashMap();
static {
// For each field f in Suit which is
// public,
// final,
// static,
// of type Suit
map.put(f.toString(), String);
}
// Conversion methods follow.
}
Still, I would need to write a separate SuitConverter class,
a ChessPieceConverter class, a BridgeDenominationConverter
class, and so on. However, perhaps I could merge these all
into one. After all, Suit.CLUBS != ChessPiece.KING. The
conversion methods all return an Object. Then, I would have
public class TypeSafeConverter implements Converter {
private final static Map map = new HashMap();
public static void register(Class tseClass) {
// Analyze tseClass,
// Insert mappings,
// Register with ConverterUtils.
}
// Converter code.
}
If no one has done anything like this, and I haven't made a
gross error, I may do it myself.
I'm writing a Struts application, and I want to go from
String values for checkboxes and radio buttons to type-safe
enumerations in my business objects without converting by hand.
Respectfully,
Eric Jablow
Praxis Engineering Technologies, Inc.
301-490-4299 x. 131.
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