RE: ActionForm automatic type conversion

Wed, 05 Jan 2005 09:33:11 -0800

Population of an ActionForm is done using Commons BeanUtils, which has a method for registering converter classes which convert strings to objects and back.

http://jakarta.apache.org/commons/beanutils/api/index.html

Specifically, the work is done by o.a.struts.util.RequestUtils.populate(...), which makes a call to the static form of o.a.c.beanutils.BeanUtils.populate:
http://jakarta.apache.org/commons/beanutils/api/org/apache/commons/beanutils/BeanUtils.html#populate(java.lang.Object,%20java.util.Map)

The static form relies on Converter classes statically registered using o.a.c.beanutils.ConvertUtils.register(...):

http://jakarta.apache.org/commons/beanutils/api/org/apache/commons/beanutils/ConvertUtils.html#register(org.apache.commons.beanutils.Converter,%20java.lang.Class)

So basically, assuming that there's exactly one conversion path from string to your object, you need to register a converter at app startup using a ServletContextListener or Plugin class.

BeanUtils has since evolved to provide more nuanced conversions (particularly not requiring that converters be registered statically) but there hasn't been call to upgrade Struts to use this. Date conversions are about the only place where I can see the need for multiple conversions from string to date in a single app. Meanwhile, managing temporary or limited-scope converters might be pretty clumsy to implement.

Hope this helps
        Joe



At 11:36 AM -0500 1/5/05, [EMAIL PROTECTED] wrote: 
ActionForm attributes are defined as Strings. In your case, a good solution
would be to define an adapter class that will do the conversion from String
to the appropriate type. Your business objects will use the converted data
types to execute the business logic. This approach is discussed in detail in
the book Struts in Action.

Bala

-----Original Message-----
From: dsarris [mailto:[EMAIL PROTECTED]
Sent: Monday, January 03, 2005 4:16 AM
To: Struts Users Mailing List
Subject: ActionForm automatic type conversion


Hi all and happy new year,

I am trying to fill an ActionForm with values that are neither Strings
or primitives. The specified values are selected using the
<html:select> tag. This a sample of my JSP code:

   <html:form action="/sumbit.do">
                        <html:select property="selectedAthlete">
                                <html:optionsCollection
                                        name="controlPanelValues"
                                        property="athletes"
                                        label="name"
                                        value="value" />

                        </html:select>
   <html:submit>
        <bean:message key="cp.button.submit"/>
   </html:submit>
   </html:form>

The "controlPanelValues" Bean contains a collection (list) named
"athletes" containing Beans of type "Pair". The "Pair" object contains
2 attributes: The "name" which is a String and the value which is an
"Athlete" object.

My ActionForm contains an attribute named "selectedAthlete" of the
type "Athlete".

However, whenever I submit this form the "selectedAthlete"  is filled
with the string representation of the "Athlete" type.

I used both simple and map-backed actionform with no success.

Is Struts capable for doing assignment of non String or primitive fields?

Chipix

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Joe Germuska [EMAIL PROTECTED] http://blog.germuska.com "Narrow minds are weapons made for mass destruction" -The Ex

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