CreatingCustomValidators

Creating a custom validator

applies to: Tapestry 4.0

this is a revised copy of a posing to the users mailing list by Scott F. Walter

1. implementing a validator

Create a class that extends org.apache.tapestry.form.validator.BaseValidator (note, this is not org.apache.tapestry.valid.BaseValidator )

Override the validate method.

If you want a parameter to be passed into your validator:

1. create a constructor that takes a String

2. add a (non abstract) property (setXXX, getXXX) where XXX will be the name of your validator. E.g. if the validator is called

mustBe, use getMustBe(), setMustBe(String). Later on you will reference the validator using: mustBe=tapestry

Here is an example:

package dummy;

import org.apache.tapestry.form.IFormComponent;
import org.apache.tapestry.form.ValidationMessages;
import org.apache.tapestry.form.validator.BaseValidator;
import org.apache.tapestry.valid.ValidatorException;

/**
 * @author scott/ron
 */
public class MustBeValidator extends BaseValidator {
 
   private String _mustBe;
   
   public MustBeValidator() {
     super();
   }
   
   public MustBeValidator(String string) {
     super(string);
   }

   public void setMustBe(String s) {
     _mustBe = s;
   }

   public String getMustBe() {
     return _mustBe;
   }

   public void validate(IFormComponent field,
             ValidationMessages messages,
             java.lang.Object object)
             throws ValidatorException {
             if (!equal(object,_mustBe) {
           throw new ValidatorException(messages.formatValidationMessage(getMessage(), "invalid-format", null));
       }                
   }

   private boolean equal(Object o1, Object o2) {
     if (o1 == null && o2 == null)
       return true;
     if (o1 == null || o2 == null)
       return false;
     return o1.equals(o2);
   }
} 

configuration

Provide a contribution to tapestry.form.validator.Validators in hivemodule.xml (stored in your WEB-INF directory)

<?xml version="1.0"?> 
<module id="myApplicationName" version="1.0.0">
     <contribution configuration-id="tapestry.form.validator.Validators">
       <validator name="mustBe" configurable="true" class="dummy.MustBeValidator"/>
   </contribution>
</module>

Note: If your validator does not take any parameters set configurable to "false" here

Using

Inside the specification file, use the new validator as follows:

<component id="firstNameField" type="TextField"> 
   <binding name="value" value="ognl:person.firstName"/>
   <binding name="validators" value="required,minLength=3,mustBe=Scott"/>
   <binding name="displayName" value="First Name"/>
 </component>