PropertyEditor converts single value but not Collection

[revengeofthepencil]

I'm having some trouble with a converter in a Spring MVC project (version 3.0.6) running on top of Hibernate 3.6.6. I have a custom object "ActionPlan" which has a plan owner and a list of plan users, all of whom are represented by "PlanUser" objects. The relevant portions of the ActionPlan object are as follows:

@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "plans_users", joinColumns = @JoinColumn(name = "plan_id"), inverseJoinColumns = @JoinColumn(name = "user_id"))
private Set<Planuser> planUsers = new LinkedHashSet<Planuser>();

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "plan_owner_id")
private Planuser planOwner;

The Controller for my edit form is loading a converter as follows:

	@InitBinder
	public void initBinder(WebDataBinder binder) {
		...
		binder.registerCustomEditor(PlanUser.class, new PlanUserEditor());
		...
	}


	private class PlanUserEditor extends PropertyEditorSupport {
		
        @Override
        public void setAsText(String text) {
        	if(StringUtils.isEmpty(text)) {
        		setValue(null);
        	} else {
            	PlanUser user = new PlanUser();
            	user.setUserID(Integer.parseInt(text));
                setValue(user);
        	}
        }
        
        @Override
        public String getAsText() {
        	if(this.getValue() == null || !(this.getValue() instanceof PlanUser) ) {
        		return null;
        	} else {
        		PlanUser user = (PlanUser)this.getValue();
    			return user.getUserID().toString();
        	}
           }
	}

Finally, the relevant portion of my edit form is as follows ("userList" is set in the controller as a complete list of all available PlanUser objects from the database):

		<tr>
			<td>Plan Owner</td>
			<td>
				<form:select path="planOwner">
					<form:options items="${userList}" itemLabel="displayName" itemValue="userID" />
				</form:select>
			</td>
		</tr>				
		
		<tr>
			<td>Plan Users</td>
			<td>
				<form:select path="planUsers">
					<form:options items="${userList}" itemLabel="displayName" itemValue="userID" />
				</form:select>
			</td>
		</tr>

It seems that the single value planOwner is working just fine - the value comes through and I can set it without any problems. However, when is comes to the planUsers Set, it doesn't seem to be parsing out the individual values. I get the following error message:

org.apache.jasper.JasperException: org.springframework.core.convert.ConversionFailedE xception: Unable to convert value "[3]" from type 'java.util.Set' to type 'java.lang.String'; nested exception is org.springframework.core.convert.ConverterNotFound Exception: No converter found capable of converting from 'com.myownbadself.PlanUser_$$_javassist_0' to 'java.lang.String'

Any help would be much appreciated.

Thanks,
Alex

[revengeofthepencil]

I actually got around this by adding another custom editor that recognizes the Set and turns it into a String containing a comma-separated list of the IDs. This seems like a hack to me, surely there must be a cleaner way to do this?