Commit 57938d2f24b6dfd089d3f4fdda905a84b6ae69f3 adds the new add-on to Roo master.

It also integrates with the current MVC scaffolding by exposing the following method signatures:

@RequestMapping(value = "/{id}", method = RequestMethod.GET, headers = "Accept=application/json")
@ResponseBody
public String showJson(@PathVariable("id") Long id) {
        return MyType.findMyType(id).toJson();
}
    
@RequestMapping(method = RequestMethod.POST, headers = "Accept=application/json")
public ResponseEntity<String> createFromJson(@RequestBody String json) {
        MyType.fromJson(json).persist();
        return new ResponseEntity<String>("MyType created", HttpStatus.CREATED);
}
    
@RequestMapping(headers = "Accept=application/json")
@ResponseBody
public String listJson() {
        return MyType.toJsonArray(MyType.findAllMyTypes());
}
    
@RequestMapping(value = "/jsonArray", method = RequestMethod.POST, headers = "Accept=application/json")
public ResponseEntity<String> createFromJsonArray(@RequestBody String json) {
   for (MyType myType: MyType.fromJsonArray(json)) {
            myType.persist();
   }
    return new ResponseEntity<String>("MyType created", HttpStatus.CREATED);
}

On a side note, the exposing of the JSON functionality can be disabled by a new attribute in the @RooWebScaffold annotation 'exposeJson' which can be set to false.

I am also adding a sample script which shows how to use the JSON methods exposed through a controller. The script works against the Roo petclinic sample application (clinic.roo).

How often do you think this will be used, compared to simply using @ResponseBody/@RequestBody on a POJO and relying on Jackson's JSON ObjectMapper? I assume you are targeting custom JSON reading/writing scenarios, but it'd be good to clarify exactly when one should be expected to use this feature.

I like this functionality, however I wish that the implementation was consistent with Spring's use of Jackson for @ResponseBody/@RequestBody.

I already use Jackson annotations to define the desired codec for my web interface. It's a drag that when I turn around and

Json() the object returned from @RequestBody the json isn't the same that from Jackson. Not sure why @ResponseBody/@RequestBody uses Jackson and this plugin uses flexjson.

Jackson appears to have richer annotation support and is already the @REST default provider. I suggest keeping this plugin's API and migrating the provider from flexjson to Jackson.