package validators;

import com.opensymphony.xwork2.validator.ValidationException;
import com.opensymphony.xwork2.validator.validators.FieldValidatorSupport;

public class NumberFieldValidator extends FieldValidatorSupport {

 public void validate(Object object) throws ValidationException {
       String fieldName = getFieldName();
       Object value = this.getFieldValue(fieldName, object);

     if (!(value instanceof String)) {
         return;
     }
  
     String str = ((String) value).trim();
     if (str.length() == 0) {
         return;
     }
  
     try {
        Double.parseDouble(str);
     }catch(NumberFormatException nfe) {
        addFieldError(fieldName, object);
      return;
     }
     try {
        Integer.parseInt(str);
     }catch(NumberFormatException nfe) {
        addFieldError(fieldName, object);
      return;
     }
  
 }
}

• The custom validator may extend the FieldValidatorSupport or the ValidatorSupport classes.
• The FieldValidatorSupport class extends ValidatorSupport to add field specific information to the Field.
• The is numeric check is performed by trying to convert the input string to Integer or Double and catching any exception.
• The addFieldError method is used add any failed validations to the list of errors to be displayed.
• The getFieldName and getFieldValue methods are implemented in the superclasses to retrieve the field name and field value for the field beign validated.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE validators PUBLIC
     "-//OpenSymphony Group//XWork Validator Config 1.0//EN"
     "http://www.opensymphony.com/xwork/xwork-validator-config-1.0.dtd">
<validators>
 <validator name="numericField" class="validators.NumberFieldValidator"/>
</validators>

 @RequiredStringValidator(type = ValidatorType.FIELD, message = "Price Required")
@CustomValidator(type = "numericField", message = "Price must be a number")
public void setPrice(String price) {
 this.price = price;
}