Question

I know this question has been asked quite a few times, however, I have a different approach of what I want to achieve.

Since Play 1.1, you’re able to match hosts. This is very useful, however, it means that for every controller, I will need to pass through the subdomain route param. This is quite a burden and repeatful if I have hundreds of controllers which use the subdomain param.

Is there not a way to create a filter which looks at the host name before everything else is executed and then sets an on-the-fly config value for that request?

For example (brainstorming), a filter would do the following:

    // use request host, but hard-coded for now...
    String host = "test.example.com";
    Pattern p = Pattern.compile("^([a-z0-9]+)\\.example\\.com$");
    Matcher m = p.matcher(host);
    if (m.matches()) {
        // OUT: test
        System.out.println(m.group(1));
        System.setProperty("host", m.group(1));
    }

And in the models I’d do something like System.getProperty("host");

I know this isn’t how it should be done, but I’m just brainstorming.

At least with this way:

1. I don’t have to pass the subdomain param through to every
   controller.
2. I don’t have to pass the subdomain param through to any models
   either
3. Models have direct access to the subdomain value so I can filter out objects that belong to the client

Also, I’m aware that System.setProperty() always applies to the entire JVM; which is a problem. I only want this value to be available throughout the duration of the request. What should I use?

Let’s analyse. How would you do it? What would be a good approach? Is this possible with Play? I’m sure there are quite a few running into this problem. Your input is highly appreciated.

Answer 1

I think you are close. If I had to do this, I would write a controller annotated with @Before and have that method extract the hostname from the request headers and put it in renderArgs.

Something like this (I haven’t tested it):

public class HostExtractor extends Controller {

    @Before
    public static void extractHost() {
       // Code to read from request headers and extract whatever you need here.
       String host = 'Your Code Here'
       renderArgs.put("hostname", host);
    }
}

Then, in your other controllers, you tell it you want to use that controller above as a filter.

@With(HostExtractor.class)
public class MyController extends Controller {

    public static void homepage() {
        String hostname = renderArgs.get("host", String.class);
        // Do whatever logic you need to render the page here.
    }
}

Again, I haven’t tested this, but I’m doing something similar to cache objects in memcache. I hope that helps!