Programming Simple Tag Handlers in JSP

Question

I recently started working on JSP, and I was going through the tutorials on creating simple tag handlers for validating custom tags. I came across this code snippet and when I tried to run it, I am getting the same error over and over again. I asks me to change the return type first, and then it tell that the new return type is incompatible with the method being overridden. Thing is, I just copied the code from docs.oracle.com

http://docs.oracle.com/javaee/5/tutorial/doc/bnann.html

Can anyone tell what's wrong here ?

EDIT : I have now added the imports and the error message.

import javax.servlet.jsp.tagext.TagData;
import javax.servlet.jsp.tagext.TagExtraInfo;
import javax.servlet.jsp.tagext.ValidationMessage;

public class TwaTEI extends TagExtraInfo {
    public ValidationMessage[] validate(TagData data) {
        Object o = data.getAttribute("attr1");
        if (o != null && o != TagData.REQUEST_TIME_VALUE) {
            if (((String)o).toLowerCase().equals("true") ||
                 ((String)o).toLowerCase().equals("false") )
                 return null;
            else
                return new ValidationMessage(data.getId(),
                    "Invalid boolean value.");
        }
        else
            return null;
    }
}

ERROR

Type mismatch: cannot convert from ValidationMessage to ValidationMessage[].

Answer 1

This part is invalid, you should return an array of ValidationMessage objects:

return new ValidationMessage(data.getId(),
                "Invalid boolean value.");

Like this:

return new ValidationMessage[]{new ValidationMessage(data.getId(),
                "Invalid boolean value.")};