@RequestParam with Lists

[hookumsnivy]

I'm trying to bind a series of parameters to a List or Array (order matters) and I'm using the RequestParam annotation. How do I go about passing the parameters.

Here is my sample controller method (I could not use the AT symbol in the post because of post restrictions so I replace it with <at>):

<at>RequestMapping
public void test(<at>RequestParam("constraints") List<String> constraints) {
    for (String constraint : constraints) {
        System.out.println(constraint);
    }
}

Is this possible?
How do I form the URL?
I tried .../test.jhtml?constraints=test1&constraints=test2 this works, but I can't find documentation indicating if the order of values is preserved or not.
I tried .../test.jhtml?constraints[0]=test1&constraints[1]=test2 but I get an error saying that the constraints parameter is required.

Note: I looked into StringArrayPropertyEditor but I would have to create a custom implementation because I can't use a set of characters as delimiters because the input is not restricted to a set of characters.

Any ideas on how to do this?

[Ben_Leedham]

When you initially create your page try passing it a List as a model attribute and bind the individual elements of the page to that list then you can retrieve it by using

public void test(@ModelAttribute("constraints") List<String> constraints){

}

[hookumsnivy]

Thanks Ben_Leedham

That didn't work, but it pointed me in the right direction.
I was unable to find a way to bind a list directly:

public void test(@ModelAttribute("constraints") ArrayList<String> constraints){

btw, you can't use just List because Spring will complain that it can't initialize it.

but it works if I put a wrapper around it:

public void test(@ModelAttribute("constraints") Contraints constraints){
...
}
    public static class Constraints {
        private List<String> items = new ArrayList<String>();

        public List<String> getItems() {
            return items;
        }

        public void setItems(List<String> items) {
            this.items = items;
        }
    }

The problem I found is that a List doesn't have a property that can be set. So the request parameter names aren't clear. When I use the Constraints object, the parameters become:
items[0], items[1], etc

[Ben_Leedham]

Glad it helped. I dint get chance to check the List advice before supplying it, so apologies if it wasn't totallly correct, but glad you sorted your problem out.

[juzerali]

I hate the fact that I have to wrap my lists around a wrapper object. A lamentable overkill.