Question

I want to use Restlet to process requests for some information, but this information takes some time to load from disk, so I want to do this step when the Restlet server is started, rather than in my Resource class, which appears to be instantiated on each request. In other words, I want to load it into memory once.

I’m looking at this tutorial: http://www.2048bits.com/2008/06/creating-simple-web-service-with.html and am assuming that each time someone requests /Users, router.attach("/users", UserResource.class); instantiates a new UserResource() object. Let’s assume I want to load the User database into memory so that the lookups in UserResource.findUser() are fast.

Update: Maybe something like this answer can help me? https://stackoverflow.com/a/7865506/318870

Update 2: I think I found a solution, so will post back soon with my findings

Answer 1

From the Restlet book and their public source code, they simply use the getApplication() function from the Resource class:

public class Application extends org.restlet.Application {

    public static void main(String... args) throws Exception {
        // Create a component with an HTTP server connector
        final Component comp = new Component();
        comp.getServers().add(Protocol.HTTP, 3000);

        // Attach the application to the default host and start it
        comp.getDefaultHost().attach("/v1", new Application());
        comp.start();
    }

    private final ObjectContainer container;

    /**
     * Constructor.
     */
    public Application() {
        /** Open and keep the db4o object container. */
        EmbeddedConfiguration config = Db4oEmbedded.newConfiguration();
        config.common().updateDepth(2);
        this.container = Db4oEmbedded.openFile(config, System
                .getProperty("user.home")
                + File.separator + "restbook.dbo");
    }

    @Override
    public Restlet createInboundRoot() {
        final Router router = new Router(getContext());

        // Add a route for user resources
        router.attach("/users/{username}", UserResource.class);

        // Add a route for user's bookmarks resources
        router.attach("/users/{username}/bookmarks", BookmarksResource.class);

        // Add a route for bookmark resources
        final TemplateRoute uriRoute = router.attach(
                "/users/{username}/bookmarks/{URI}", BookmarkResource.class);
        uriRoute.getTemplate().getVariables().put("URI",
                new Variable(Variable.TYPE_URI_ALL));

        return router;
    }

    /**
     * Returns the database container.
     * 
     * @return the database container.
     */
    public ObjectContainer getContainer() {
        return this.container;
    }
}


/** resource class (UserResource.java) has these functions
/**
 * Returns the parent application.
 * 
 * @return the parent application.
 */
@Override
public Application getApplication() {
    return (Application) super.getApplication();
}

/**
 * Returns the database container.
 * 
 * @return the database container.
 */
public ObjectContainer getContainer() {
    return getApplication().getContainer();
}