Spring 3, JSR-303 (bean validation) and validating collection

Question

I have a simple class Foo, saying like this one :

public class Foo {
    @NotNull
    private String bar;
    public String getBar(){ return bar; }
    public void setBar(String _bar){ this.bar = _bar; }
}

Now, I have a controller REST method that take an array (or collection) of Foos where I want to ensure every Foo has a non-null bar property. I thought using the @Valid annotation would make the trick, but it seems it isn't :

@Controller
public class MyController {
    @RequestMapping(value="/foos", method=RequestMethod.POST)
    public @ResponseBody String createFoos(@Valid @RequestBody Foo[] foos){
        // blah blah blah
        return "yeah";
    }
}

Note: It doesn't work with a List<Foo> either. But with a unique Foo it works !

Looks like Spring validation doesn't work when we have "multiple" objects (in collection or array).

I even tried to implement a HandlerMethodArgumentResolver with a custom annotation, but I don't know how to define "indexed property names" in BindingResult.

If someone knows a workaround for this problem, it would be greatly appreciated ! :)

Answer 1

There's a few things I think you've missed in your implementation. You'll want to use the notion of object graphs to make this work.

Your class Foo has the @NotNull validation on one of its fields, however you haven't really expressed what needs to be valid with the collection.

From the Hibernate Reference:

Object graph validation also works for collection-typed fields. That means any attributes that are arrays, implement java.lang.Iterable (especially Collection, List and Set) or implement java.util.Map can be annotated with @Valid, which will cause each contained element to be validated, when the parent object is validated.

So your code would become

@Controller
public class MyController {
    @RequestMapping(value="/foos", method=RequestMethod.POST)
    public @ResponseBody String createFoos(@Valid @NotNull @RequestBody Foo[] foos){
        // blah blah blah
        return "yeah";
    }
}