Class LazyValidatorForm

There isn't really that much to this implementation as most of the lazy behaviour is in LazyDynaBean and wrapping the LazyDynaBean is handled in the parent BeanValidatorForm. The only thing it really does is populate indexed properties which are a List type with a LazyDynaBean in the get(name, index) method.

Lazy DynaBeans provide several types of lazy behaviour:

• lazy property addition - properties which do not exist are automatically added.
• lazy List facilities - automatically grows a List or Array to accomodate the index value being set.
• lazy List creation - automatic creation of a List or Array for indexed properties, if it doesn't exist.
• lazy Map creation - automatic creation of a Map for mapped properties, if it doesn't exist.

Using this lazy ActionForm means that you don't have to define the ActionForm's properties in the struts-config.xml. However, a word of warning, everything in the Request gets populated into this ActionForm circumventing the normal firewall function of Struts forms. Therefore you should only take out of this form properties you expect to be there rather than blindly populating all the properties into the business tier.

Having said that it is not necessary to pre-define properties in the struts-config.xml, it is useful to sometimes do so for mapped or indexed properties. For example, if you want to use a different Map implementation from the default HashMap or an array for indexed properties, rather than the default List type:

   <form-bean name="myForm" type="org.apache.struts.validator.LazyValidatorForm">
     <form-property name="myMap" type="java.util.TreeMap" />
     <form-property name="myBeans" type="org.apache.commons.beanutils.LazyDynaBean[]" />
   </form-bean>
 

Another reason for defining indexed properties in the struts-config.xml is that if you are validating indexed properties using the Validator and none are submitted then the indexed property will be null which causes validator to fail. Pre-defining them in the struts-config.xml will result in a zero-length indexed property (array or List) being instantiated, avoiding an issue with validator in that circumstance.

This implementation validates using the ActionForm name. If you require a version that validates according to the path then it can be easily created in the following manner:

    public class MyLazyForm extends LazyValidatorForm {

        public MyLazyForm () {
            super();
            setPathValidation(true);
        }

    }
 

Rather than using this class, another alternative is to either use a LazyDynaBean or custom version of LazyDynaBean directly. Struts now automatically wraps objects which are not ActionForms in a BeanValidatorForm. For example:

   <form-bean name="myForm" type="org.apache.commons.beanutils.LazyDynaBean">
     <form-property name="myBeans" type="org.apache.commons.beanutils.LazyDynaBean[]" />
   </form-bean>