Using Validate Method of ActionForm to validate JSP

Question

Hi...
Am working on a struts application in which i have a struts jsp page which will contain a table of records that am populating while loading the page itself, each record of the table will have a check box associated with it.
my requirement is that, i must select atleast one checkbox from the list of records before going for further processing from the page ie. i must validate whether the the user had selected any one of the check boxes. i am not usings struts validation plugin for this, instead am going for overrideing the validate method of ActionForm in my form bean.
Now comes my problem:
When i tried to validate the page without selecting any of the check boxes,the validate method is being called and its checking the values and returning the error message to my jsp page, but by the time the msg comes back to the jsp page the page is getting refreshed and all the previous list of records i had displayed in the page is lost giving me an error msg on jsp that "collection not found". The application scope is set to request and not to session. So i tried with setting the scope to session (which was not permissible by my requirements, still just for testing) but still am geting the same error
i am stuck up with this problem for a long time and i couldnt find out any one who could solve it, and i have to use the Validate method of Action Form
Please any one can explain whats the problem and what should i do
Thanks in advance
Rens

Answer 1

ok, i'm going to try and make this short and sweet. let me know if you run into problems.
first off, you may need to add apache commons-collections to your project.
#1
you will need to make a new bean class to represent your 'line' object. so if it was a Person we'd make a Person class with a String name, int age... blah blah blah.
#2
in your ActionForm class, add a
java.util.List personList;and make a normal setter and getter for it
#3
this is the only tricky part, make (or add this to) your reset( ) function in your ActionForm...
public void reset(ActionMapping actionMapping, HttpServletRequest httpServletRequest) {
     personList = ListUtils.lazyList(new java.util.ArrayList(), new Factory() {
          public Object create() { return new Person(); }
}but replace the 'new Person()' part with whatever the bean class you made in Step 1 is
#4
now, in your Action class build the list of objects from the database, and set it into your form.
#5
in your .jsp code you will need to use the nested tags like so
<nested:iterate id="personLine" property="personList">
          <TR>
               <td><nested:write property="name"/></td>
               <nested:hidden property="age"/>
          </TR>
</nested:iterate>
#6
then back in your validate code or in your Action class you can access the list by calling yourForm.getPersonList() and validating it. if you find a problem and return with an error all the values will remain without having to talk to the database again.
hope that helps.