Interfaces and @RequestBody

Question

I'm currently working on a project which allows users to book (via the web) the use of a chosen resource for a given period of time. In this program I am trying to keep with Spring's philosophy (and the general best practice) of programming to interfaces and as such I try to use interfaces anywhere where functionality is repeated among concrete classes.

One interface I have created is called a BookableResourceController which specifies the methods needed by a controller to handle the minimum required functionality for any type of resource to be booked. I also make use of a second interface, BookableResource, which identifies which objects model a resource that is allowed to be booked through the application.

The problem I am currently running into is that a few of the methods defined by BookableResourceController use the @RequestBody mapping to convert a JSON object into a method parameter, and since Jackson can only convert JSON into "SimpleType" objects, I receive an error if I specify the input parameter to be a BookableResource.

@RequestMapping(value="/delete.html", method = RequestMethod.POST)  
public ModelAndView processDeleteResource(
    @RequestBody BookableResource resource); 

Can not construct instance of org.codehaus.jackson.map.type.SimpleType, problem: abstract types can only be instantiated with additional type information

From what I can tell this error means that I will need to define a specific implementation of BookableResource, meaning I will most likely need to exclude these methods from the interface even though any controller that is to be used for this purpose will require those methods.

What I am asking is if anyone knows a way to define an interface as the object that is expected from an @RequestBody mapping using JSON, or does anyone have any suggestions of how to structure my contoller interface in order to include these methods?

Cheers

Answer 1

I'm not sure it would work, but you can try to make it generic:

public interface BookableResourceController<R extends BookableResource> {
    @RequestMapping(value="/delete.html", method = RequestMethod.POST)
    public ModelAndView processDeleteResource(@RequestBody R resource); 
}