| Struts Lazy ActionForm which wraps a
LazyDynaBean.
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>
version:
$Rev: 471754 $ $Date: 2005-05-07 12:11:38 -0400 (Sat, 07 May 2005)
version:
$
See Also: Commons
* BeanUtils JavaDoc
since:
Struts 1.2.6 | 