Everyday Gaelyk: Simplify flow in groovlets by handling their return values

Gaelyk plugin system allows you to define after hook which is called when groovlet execution is finished. Since Gaelyk 2.0 the result returned from the groovlet is bound to the after closure so you can e.g. turn that result into the JSON response.

Let say you have a groovlet serving some JSON content by id and you want to simplify it’s flow.

JSON groovlet, standard version

 response.contentType = 'application/json'

 if(users.isUserLoggedIn){
     response.status = 401
     json(error: 'You must be logged in') 
 } else {
     // uses @Entity annotation
     Item item = Item.get(params.id as long)
     if(!item){
         response.status = 404
         json(error: 'Item not found')
     } else {
         json(id: item.id, title: item.title)
     }
 }

In fact, this example is pretty trivial but still it would be handy if we can cut off some unnecessary branching:

JSON groovlet, version with plugin

 // see following
 request.renderAsJson = true

 if(users.isUserLoggedIn){
     return [status: 401, error: 'You must be logged in'] 
 }

 // uses @Entity annotation
 Item item = Item.get(params.id as long)
 if(!item){
     return [status: 404, error: 'Item not found']
 }
 
 [id: item.id, title: item.title]

This can be actually quite simply accomplished by creating plugin which will render groovlet result as JSON. You can follow the guide on Gaelyk website. Basically, you need a script containing the after handler:

JSON renderer plugin

after {
    // render as json only when this attribute is set to groovy truth
    if(request.renderAsJson){
        // sets the json
    response.contentType = 'application/json'
        // result is stored in 'result' closure variable
    if(result instanceof Map && result?.status){
            // set the status from the status map value
        response.status = result.remove('status') as int
    }
        // render the result
    JsonBuilder json = new JsonBuilder()
    json result
    json.writeTo(response.writer)
    }
}

Save the script as WEB-INF/plugins/jsonRenderer.groovy and create another file WEB-INF/plugins.groovy with single line install jsonRenderer and you can try it yourself in your Galeyk 2.0 application.

If you got another idea how to use result of groovlet exection in your application, please, leave a message under the post.