How to use MessageFormat and ActionError together?

Question

i'm trying to use the Message Format class to format a message in the sense that i want to concatenate two strings first and then pass that one string to the ActionError.
My first string defined in a properties file is:
error.invalid="{0} is invalid."My second string defined in the code itself is
String fieldname="User Name";What I am trying is to form one string "User Name is invalid" and pass that to the ActionError in the following way:
if (!isThisAValidField((String) map.get("username")))
String fieldname = "User Name";
errors.add("user", new ActionError(MessageFormat.format("error.invalid", fieldname)));
}This is the first time I am trying to do this and it does not work! The output just shows: {0} is invalid.
Any ideas/help where I am going wrong will be very help. Thanks!

Answer 1

I think I am using the MessageFormat class from the standard API. In a seperate program, I have everything working fine. This is the program:
package mytestproject;
import java.text.*;
public class Main
public static void main(String[] args)
String field = "User-ID";
String error = "{0} is invalid";      
System.out.println(MessageFormat.format(error, field));       
}When I run this program, I get the desired output: User-ID is invalid.
the first parameter would be the string extracted from the properties file, not the property name anyway.In the program above I used the first parameter as a sample of what would be in the properties file and the second parameter was the field name. And it worked fine.