DDevelopment & Design

Adding diff to Gitorious push notification emails

One thing we were really missing in

Gitorious is lack of diff in email notifications. We were using this feature in SVN for “quick code review”. Before we moved to Gitorious, we were using Gitolite where it was possible to configure it with git .hooks. However in Gitorious you do not have easy access to your repository directory ( it’s hashed ). So I have started googling about the feature. I have found in Gitorious a misterious feature called webhooks. But what it does is sending HTTP requests with JSON objects about commits, but without diff body. After loosing few more hours on google, forums and different groups I decided to try to implement this feature on my own. Few more hours to understand this mysterious ( for me ) Ruby on Rails code of Gitorious and I have localized few files that I should change to make it working. After all I have to say it was quite simple. The core are two lines that create commit diff in lib/event_rendering/text.rb:   repo = Repository.find_by_name_in_project!(event.target.name, event.project) diff_content = repo.git.git.show({}, [start_sha, end_sha].join(“..”))   (If you would like to modify content of the commit diff you just have to modify this git.git call ). Rest of the code is just for putting diff_content value into email :). You can review the whole patch here. After applying the patch please remember to restart git-poller and subscribe in Gitorious to email notification.

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DDevelopment & Design

Simple trick to DRY your Grails controller

Grails controllers are not very DRY. It's easy to find duplicated code fragments in default generated controller. Take a look at code sample below. It is duplicated four times in show, edit, update and delete actions:

class BookController {
def show() {
def bookInstance = Book.get(params.id)
if (!bookInstance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
return
        }
        [bookInstance: bookInstance]
    }
}

Why is it duplicated?

There is a reason for that duplication, though. If you move this snippet to a method, it can redirect to "list" action, but it can't prevent controller from further execution. After you call redirect, response status changes to 302, but after method exits, controller still runs subsequent code.

Solution

At TouK we've implemented a simple trick to resolve that situation:

  1. wrap everything with a simple withStoppingOnRender method,
  2. whenever you want to render or redirect AND stop controller execution - throw EndRenderingException.

We call it Big Return - return from a method and return from a controller at once. Here is how it works:

class BookController {
def show(Long id) {
withStoppingOnRender {
Book bookInstance = Book.get(id)
validateInstanceExists(bookInstance)
            [bookInstance: bookInstance]
        }
    }

protected Object withStoppingOnRender(Closure closure) {
try {
return closure.call()
        } catch (EndRenderingException e) {}
    }

private void validateInstanceExists(Book instance) {
if (!instance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
throw new EndRenderingException()
        }
    }
}

class EndRenderingException extends RuntimeException {}

Example usage

For simple CRUD controllers, you can use this solution and create some BaseController class for your controllers. We use withStoppingOnRender in every controller so code doesn't look like a spaghetti, we follow DRY principle and code is self-documented. Win-win-win! Here is a more complex example:

class DealerController {
@Transactional
def update() {
withStoppingOnRender {
Dealer dealerInstance = Dealer.get(params.id)
validateInstanceExists(dealerInstance)
validateAccountInExternalService(dealerInstance)
checkIfInstanceWasConcurrentlyModified(dealerInstance, params.version)
            dealerInstance.properties = params
saveUpdatedInstance(dealerInstance)
redirectToAfterUpdate(dealerInstance)
        }
    }
}