DDevelopment & Design

How to test Spring session scoped beans

I wanted to use the http session just as a repository (database/files), to keep facebook access token for currently logged user. While I can manipulate session directly, another option is to declare the class as a session scoped bean in Spring. Somet…

I wanted to use the http session just as a repository (database/files), to keep facebook access token for currently logged user. While I can manipulate session directly, another option is to declare the class as a session scoped bean in Spring. Something like this:

public class RepositoryOnHttpSession {
    private String facebookAccessToken;

    public FacebookTemplate getFacebookTemplate() {
        return new FacebookTemplate(facebookAccessToken);
    }

    public void setFacebookAccessToken(String facebookAccessToken) {
        this.facebookAccessToken = facebookAccessToken;
    }    
}

<bean id="repositoryOnHttpSession" class="pl.touk.storytelling.infrastructure.repositories.RepositoryOnHttpSession" scope="session">
    <aop:scoped-proxy/>
</bean>

<aop:scoped-proxy/> makes Spring IoC container create a cglib proxy, and inject that to other singleton type beans instead. All nice and cool, except integration tests (which get Spring IoC container to inject all the dependencies) are blowing up with:

java.lang.IllegalStateException: No Scope registered for scope ‘session’

While there’s a lot of solutions to be googled (including redeclaring the object as a prototype/sinlgeton for test context, injecting mock http session and request), the easiest way to have a simple thread-bound session scope is just to declare it in the TEST IoC configuration, like below. Just keep in mind that junit fires all tests in a single thread by default, so the state is persisted between tests. You may need to clean it up in @After.

<bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
    <property name="scopes">
        <map>
            <entry key="session">
                <bean class="org.springframework.context.support.SimpleThreadScope"/>
            </entry>
        </map>
    </property>
</bean>

Solution Architect @ TouK

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We wtorek (19 04 2011) dowiemy się co dobrego można znaleźć w JDK7.

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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)
        }
    }
}