It is possible to use CDI and Weld in a Java command line program. There are several options to bootstrap the CDI container. Weld offers a special Main class that does the job for us. But sometimes we just want to shield the CDI dependencies and provide our own main method. Now comes the tricky part: how do we pass command line arguments to the container, or even boot managed beans by injecting command line argument?
The answer is simple: use a static producer method! Here is an example:
@Singleton
public final class Main {
private static final Logger LOGGER = LoggerFactory.getLogger(Main.class);
private static Configuration CONFIGURATION;
@Produces
public static Configuration configuration() {
return CONFIGURATION;
}
@Inject
ProjectSpecificBean instance;
public void run() throws IOException {
// Use injected instace
}
public static void main(String[] args) throws IOException {
// Initialize the Configurtation instance by command line arguments
// and store it in a static field. Now it is available by the producer method
CONFIGURATION = new Configuration(args);
// Initialize Weld
Weld theWeld = new Weld();
WeldContainer theContainer = theWeld.initialize();
// Execute the run method
theContainer.instance().select(Main.class).get().run();
// Shutting down Weld again
theWeld.shutdown();
}
}Note that ProjectSpecificBean requires a container managed Configuration instance. This is acquired by the configuration() static producer method.
Quite simple. I really love CDI, even in a Java SE environment.
Git revision: 63a36b0