multiselect form inputs only populate first string selected

[Adam Murray]

When I try to use a multiselect input (html:select multiple=true), it
works fine as long as the associated property is a String[]. However,
there's a situation where I have a dynamic list of form elements, each
of which has its own multiselect input. So I tried changing the property
to a List, but then only the first String selected on the webform is
populated in the applicable List index.

I threw in some debugging output in my ActionForm setter methods to try
to see what was going on. In the case where I use a String[] directly,
the object being set is a String[] as expected, but in the case where I
wrap a List around the property, the object being set is just a String.
I tried using a the Map-backed approach instead of a List, but with the
same results: I only see the first item selected off the multiselect
box, and never see the other strings that are selected.

Has anyone encountered this problem before? Is it perhaps a bug in
Struts or am I doing something wrong?

-Adam

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multiselect with a map-backed form property

[Adam Murray]

I have a form with a dynamically generated list of constraints that can
be turned on or off, and each constraint has a set of values associated
with it. My form has two relevant fields:

private String[] selectedConstraints;
private Map values;

public String[] getSelectedConstraints() {
return selectedConstraints;
}
public void setSelectedConstraints(String[] selectedConstraints) {
this.selectedConstraints = selectedConstraints;
}

public Object getValues(String key) {
return values.get(key);
}
public void setValues(String key, Object value) {
values.put(key, value);
}


To keep track of which values are associated with which constraint, I
use the string from the selectedConstraints array as the key into the
values map. My jsp page looks like this:

c:forEach var=constraint items=${constraints}

  trtd

html:multibox property=selectedConstraints
  c:out value=${constraint.propertyID}/
/html:multibox
c:out value=${constraint.propertyName}/

  /tdtd

 html-el:select property=values(${constraint.propertyID})
   html:optionsCollection name=constraint
property=allowableValues/
 /html-el:select
...


The above works perfectly fine as long as only want to select a single
item from the select drop-down box. The problem is some of the
constraints can have multiple values, so I changed the select to a
multi-select:

 html-el:select multiple=true
property=values(${constraint.propertyID})

But then the form is only ever populated with the *first* string
selected from the multiselect box. Since a map can hold a String[] as
easily as a String, I'm a little confused by this behavior. I tried the
following things with no luck (these changes are in the struts action
that forwards to the jsp above):

1) inserting an empty String array into the values map for each key in
an attempt to coerce the user of String arrays

2) inserting a wrapper class into the map for each key:
public class SelectedValues {
private String[] selectedValues;
public String[] getSelectedValues() {   
return selectedValues;
}
public void setSelectedValues(String[] selectedValues) {
this.selectedValues = selectedValues;
}
}

and I updated my jsp to:
 html-el:select multiple=true
property=values(${constraint.propertyID}).selectedValues

but that causes the following exception:
javax.servlet.ServletException: BeanUtils.populate
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:1254)
...
root cause:
java.lang.IllegalArgumentException: No bean specified

org.apache.commons.beanutils.PropertyUtils.getPropertyDescriptor(PropertyUtils.java:837)
...


I can get the multiselect to work if I create a String array for each
constraint, but that defeats the purpose since this is supposed to be
dynamically generated. I'm out of ideas for other things to try with the
map-backed approach. Can someone tell me what I'm doing wrong here?

Thanks,
Adam

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