Preloader image

Tomcat CDI

Tomcat + Java EE = TomEE, the Java Enterprise Edition of Tomcat. With TomEE you get Tomcat with CDI added and integrated and ready to go!

import javax.annotation.Resource;
import javax.enterprise.inject.spi.BeanManager;
import javax.inject.Inject;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class MyServlet extends HttpServlet {

    @Inject
    private Car car;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        car.drive();

    }
}

Where Car could be any POJO with a no-arg constructor. Additionally it’s quite easy to create a factory to create the car you want injected. Simply do as follows:

import javax.enterprise.inject.Produces;

public class AssemblyLine {

    @Produces
    public Car createFancyCar() {
        return new Car("Ferrari", "458 Italia", 2012);
    }
}

So when will the Car be created? In the above it will be created when MyServlet is created. If you annotate createFancyCar with @RequestScoped it will be created once per http request and shared by everyone in the request. If you annotate createFancyCar with @SessionScoped it will be created once per HttpSession and shared by everyone in the same session. So no more repeatedly putting and getting into the HttpSession by hand, just let the container do it!

No need to add even a single library! To make the above work all you need is a META-INF/beans.xml file in your webapp like the following:

<beans/>

Any jar in your webapp with the above will automatically be CDI enabled and all those beans can be injected with @Inject with no need to make them EJBs or third party frameworks.

All this is setup and ready to go! Spend your time learning and having fun and writing your app, don’t spend it chasing down libraries and integrating things the hard way.

Download TomEE and you’re minutes away from having fun with CDI on Tomcat.

Unresolved directive in <stdin> - include::apache-tomee.adoc[leveloffset=+1]