@MessageMapping with Grails spring-websocket plugin

Question

I am a Grails newbie and working on getting WebSockets working in an application. I got most of it working except I couldn't figure out how to pass parameters to the methods annotated with @MessageMapping.

This works:

class MyController{
    @MessageMapping(value="/start")
    protected void startProcess(){ }
}

What I need something like this to work:

 @MessageMapping(value="/start/{file}")
 protected void startProcess(){ 
     String file = params.file
     //do somethig with the file...
 }

But it doesn't work. I have tried changing UrlMappings.groovy, @PathVariable. I am pretty sure I am missing something simple. Any pointers?

Answer 1

To get something form the path use @DestinationVariable (see 20.4.4 Annotation Message Handling in the spring websocket documentation).

Here is a working snippet (grails 2.4.3, based on the plugin example):

// Domain Class
class Foo {
    String name
    String desc
}

// controller method
@MessageMapping("/hello/{file}")
@SendTo("/topic/hello")
protected String hello(@DestinationVariable String file, @Payload Foo foo) {
    return "received: ${file} ${foo}"
}

// javascript
client.send("/app/hello/FILE", {}, JSON.stringify({
    'name': "foo",
    'desc': "a foo"
}));