Constructor dependency injection with Servlet 3.0?

Question

Since Servlet 3.0 it is possible to register Servlet instances programmatically with javax.servlet.ServletContext#addServlet. This class has also a createServlet method which analyses some annotations and performs dependency injection. I wonder if I need this method if I don't need the annotation processing. I'd like to have a servlet with a usual constructor to set required dependencies via dependency injection.

@Inject
public MyServlet(SomeDependency sd) {  // Constructor
  ...
}

Questions:

• Is it possible to construct a servlet instance "by hand" without createServlet? (new MyServlet())
• Is it possible to use the dependency injection mechanism of a Java EE server to perform constructor injection? How to do it? Or is a separate DI framework like Guice required?

Answer 1

The recent Java EE 6 standard now supports dependency injection for servlets, the relevant part is called JSR-299 or CDI. The JSR-299 reference implementation, JBoss weld, can be deployed into servlet containers like Tomcat or Jetty as well if you don't want to use a full Java EE 6 application server like glassfish v3 e.g.

By the way, with an embedded Jetty server you can use its custom API to add preconfigured servlet instances.

Answer 2

Guice does this out of the box without the need for Java EE servers.

http://code.google.com/p/google-guice/wiki/ServletModule