Using @Context, @Provider and ContextResolver in JAX-RS

Question

I\'m just getting acquainted with implementing REST web services in Java using JAX-RS and I ran into the following problem. One of my resource classes requires access to a s

Answer 1

A pattern that works for me: Add some fields on your Application subclass that provide the objects you need to inject. Then use an abstract base class to do the "injection":

public abstract class ServiceBase {

    protected Database database;

    @Context
    public void setApplication(Application app) {
        YourApplication application = (YourApplication) app;
        database = application.getDatabase();
    }
}

All your services that need to access the database may now extend ServiceBase and have the database available automatically via the protected field (or a getter, if you prefer that).

This works for me with Undertow and Resteasy. In theory this should work across all JAX-RS implementations since injection of the Application is supported by the standard AFAICS, but I haven't tested it in other settings.

For me, the advantage over Bryant's solution was that I don't have to write some resolver class just so I can get at my application-scoped singletons like the database.