Wicket is providing many build-in validators for developers, EqualInputValidator is best for compare two form components identity. However Wicket’s didn’t provide any validator for form component not equal checking. Here i take EqualInputValidator as a reference and create a new custom validator “NotEqualInputValidator“, so that we can compare the not equal of two form components.

NotEqualInputValidator in Wicket

import org.apache.wicket.markup.html.form.Form;
import org.apache.wicket.markup.html.form.FormComponent;
import org.apache.wicket.markup.html.form.validation.AbstractFormValidator;
import org.apache.wicket.util.lang.Objects;
 
public class NotEqualInputValidator extends AbstractFormValidator
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
 
	/** form components to be checked. */
	private final FormComponent<?>[] components;
 
	/**
	 * Construct.
	 * 
	 * @param formComponent1
	 *            a form component
	 * @param formComponent2
	 *            a form component
	 */
	public NotEqualInputValidator(FormComponent<?> formComponent1, 
                          FormComponent<?> formComponent2)
	{
		if (formComponent1 == null)
		{
			throw new IllegalArgumentException("argument formComponent1 cannot be null");
		}
		if (formComponent2 == null)
		{
			throw new IllegalArgumentException("argument formComponent2 cannot be null");
		}
		components = new FormComponent[] { formComponent1, formComponent2 };
	}
 
 
	public FormComponent<?>[] getDependentFormComponents()
	{
		return components;
	}
 
 
	public void validate(Form<?> form)
	{
		// we have a choice to validate the type converted values or the raw
		// input values, we validate the raw input
		final FormComponent<?> formComponent1 = components[0];
		final FormComponent<?> formComponent2 = components[1];
 
		if (Objects.equal(formComponent1.getInput(), formComponent2.getInput()))
		{
			error(formComponent2);
		}
	}
 
}

How to use 

private PasswordTextField passwordTF;
private PasswordTextField cpasswordTF;
 
//...initialize the text field
 
add(new NotEqualInputValidator(oldpasswordTF,passwordTF));