How to enable CORS in Grails 3.0.1

Question

I would like to do cross origin communication using Grails in server side. The only documentation that I found is this one

https://grails.org/plugin/cors

but thi

Answer 1

I was playing around with the emberjs framework together with a Grails 3.0 rest application when I was hit by the CORS issue. Following the steps in this article http://www.greggbolinger.com/rendering-json-in-grails-for-ember-js/ helped me get further.

The article shows how you can use the new Interceptors to create a CorsInterceptor class which sets the correct headers.

class CorsInterceptor {

  CorsInterceptor() {
    matchAll()
  }

  boolean before() {
    header( "Access-Control-Allow-Origin", "http://localhost:4200" )
    header( "Access-Control-Allow-Credentials", "true" )
    header( "Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE")
    header( "Access-Control-Max-Age", "3600" )
    true
  }

  boolean after() { true }
}

This worked as expected for GET requests, but failed for POST and PUT requests. The reason for this was that an OPTIONS preflight request was sent first to http://localhost:8080/mycontroller/1234, which in my case caused a 404 not found to be returned.

With the help from this answer https://stackoverflow.com/a/31834551 I modified the CorsInterceptor class to this instead:

class CorsInterceptor {

   CorsInterceptor() {
    matchAll()
  }

  boolean before() {
    header( "Access-Control-Allow-Origin", "http://localhost:4200" )
    boolean options = ("OPTIONS" == request.method)
    if (options) {

        header( "Access-Control-Allow-Origin", "http://localhost:4200" )
        header( "Access-Control-Allow-Credentials", "true" )
        header( "Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE")
        header( "Access-Control-Max-Age", "3600" )

        response.status = 200
    }

    true 
  }

  boolean after() { true }

}

Now POST and PUT requests were working.