You surely noticed that we are using Jersey here. Why? Because Jersey is one of the reference implementations for JAX-RS, which means that it implements all JAX-RS specifications.
Moreover, with Jersey, we can use Grizzly to start a small local server, which will be useful for this recipe, as we need just a few server features to show the SSE behavior.
Further on in this book, we will use a full GlassFish to build more JAX-RS recipes.