Jakarta Struts Cookbook

8.10. Adding a Custom Validation to a Validator Form

Problem

You need to add a custom ad hoc validation check to a Validator ActionForm.

Solution

Extend the ValidatorForm or ValidatorActionForm and override the validate( ) method, ensuring you call super.validate( ) to perform the Validator's validation. (See Example 8-14.)

Example 8-14. Extending the ValidatorForm

import javax.servlet.http.HttpServletRequest;

import org.apache.struts.action.ActionError;
import org.apache.struts.action.ActionErrors;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.validator.ValidatorForm;

public final class MyForm extends ValidatorForm {
    private String foo;
    private String bar;

    public String getFoo( ) {
        return foo;
    }
    public void setFoo(String s) {
        foo = s;
    }
    public String getBar( ) {
        return bar;
    }
    public void setBar(String s) {
        bar = s;
    }
    public ActionErrors validate(ActionMapping mapping, 
                                 HttpServletRequest request) {
        // Perform validator framework validations
        ActionErrors errors = super.validate(mapping, request);
      
        // Add crossfield and business validations here
        if (!checkFooBarValid(foo, bar)) {
            errors.add("foo", new ActionError("errors.invalidFooBar"));
        }
        // additional validations ...

        return errors;
    }

    private boolean checkFooBarValid(Foo foo, Bar bar) {
        boolean valid = false;
        // perform custom validation
        valid = FooBarUtil.checkFooBar(foo, bar);
        return valid;
    }
}

If you're using a dynamic form defined in the struts-config.xml, extend the type being used (e.g., DynaValidatorForm ...