Accessing the AppKernel environment variable in symfony 2

It's also possible to get that as a parameter. If you take a look at the \Symfony\Component\HttpKernel\Kernel class you'll find a getKernelParameters() method that exposes all the kernel parameters.

/**
 * Returns the kernel parameters.
 *
 * @return array An array of kernel parameters
 */
protected function getKernelParameters()
{
    $bundles = array();
    foreach ($this->bundles as $name => $bundle) {
        $bundles[$name] = get_class($bundle);
    }

    return array_merge(
        array(
            'kernel.root_dir' => realpath($this->rootDir) ?: $this->rootDir,
            'kernel.environment' => $this->environment,
            'kernel.debug' => $this->debug,
            'kernel.name' => $this->name,
            'kernel.cache_dir' => realpath($this->getCacheDir()) ?: $this->getCacheDir(),
            'kernel.logs_dir' => realpath($this->getLogDir()) ?: $this->getLogDir(),
            'kernel.bundles' => $bundles,
            'kernel.charset' => $this->getCharset(),
            'kernel.container_class' => $this->getContainerClass(),
        ),
        $this->getEnvParameters()
    );
}

So in a services.yml file you can get the environment with %kernel.environment% whilst in a container aware class you can get it by doing:

$this->getContainer()->getParameter('kernel.environment');

see Kernel.php class on github

The default entity classes generated by the console don't inherit anything. This means they aren't "ContainerAware" in any way.

And generally speaking, I don't think they should be. I supposed it depends on what you're doing but you could handle this with some basic dependency injection

In a controller:

$entity = new \Your\Bundle\Entity\Foo(
  $this->container->get( 'kernel' )->getEnvironment()
);

And then in src/Your/Bundle/Entity/Foo.php

private $env;

public function __construct( $env=null )
{
  $this->env = $env;
}

Would this work for you?

P.S. The event listener you posted about is for Controllers - not for arbitrary classes.