Using @Form and @FormParam, it is not possible to have RESTEasy inject values to a Map when the request parameter names are non-alphabetic. For instance, if we have a request parameter:

myMap[b794c4a0-14b7-0130-c2da-20c9d04983db].bar=test

And @Form/@FormParam annotated classes:

    public class MyForm
    {
        @Form( prefix = "myMap" )
        private Map<String, Foo> myMap = Maps.newHashMap();
    }

    public class Foo
    {
        @FormParam( "bar" )
        public void setBar( final String bar )
       { ... }
    }

And a resource accepting a form-url-encoded POST:

    @Path( "/test" )
    public class MyController
    {
        @Consumes( MediaType.APPLICATION_FORM_URLENCODED )
        @POST
        public void doPost( @Form final MyForm myForm )
        { ... }
    }

The myForm.myMap will not have an entry with a key "b794c4a0-14b7-0130-c2da-20c9d04983db".

It looks like the problem occurs because of a regex in MapFormInjector. The regex ("^" + prefix + "\\[([a-zA-Z_]+)
]") only allows alphabetic characters and underscore characters when matching form parameters.