Spring IoC和Java EE

Question

In Spring through the ApplicationContext class I can utilise IoC features and get a reference to a bean as follows

public class Driver {

    public static void main(String args[])
    {
      ApplicationContext applicationContext = new ClassPathXmlApplicationContext("/spring-config.xml");

      MyClass myClass = (MyClass)applicationContext.getBean("myClass");

}

I would like to be able to do the same with Java EE, but I don't seem to be able to outside of an application server.

I'm trying the following

public class Driver {

  public static void main(String args[])
  {

    InitialContext ic;

    try {

        ic = new InitialContext();
        // JNDI lookup
        MyClass myClass = (MyClass)ic.lookup("java:module/MyClass");            
    } catch (NamingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (SecurityException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


}

So far with this approach I get a javax.naming.NoInitialContextException. My question is how can load up IoC features in a standalone application using Java EE?

EDIT Thanks for the help guys...I went with the OpenWebBeans CDI implementation... Thanks for the help.

Answer 1

Currently you are working with JNDI , not an IoC.

If you want JNDI worked in standalone application to locate remote data google for "jndi client".

If you want to use IoC in your Java EE application - check CDI

Answer 2

If you need to get JNDI resource outside web-container or application server, then before lookup you need to bind resource. But before binding you need to implement and register javax.naming.spi.InitialContextFactory implementation.

In the easiest way I would suggest to keep all bindings in the global java.util.concurrent.ConcurrentHashMap . So it should look like the following (please keep in mind that this is easiest solution, and it might not work properly in some cases, but it satisfies your particular request):

public class Driver {

    //static initializtion
    static {
        //registering you custom InitialContextFactory
        //note, that you can register it in some other way, check http://docs.oracle.com/javase/jndi/tutorial/beyond/env/source.html
        System.setProperty("java.naming.factory.initial", SimpleInitialContextFactory.class.getName());

        bindMyClass();
    }

    private static void bindMyClass(){
        try {
            InitialContext context = new InitialContext();
            context.bind("java:module/MyClass", new MyClass());
        } catch (NamingException ignored) {}
    }

    public static void main(String args[]) throws Exception {
        InitialContext ic = new InitialContext();
            // JNDI lookup
        MyClass myClass = (MyClass)ic.lookup("java:module/MyClass");//should find it
    }
}

class SimpleInitialContextFactory implements InitialContextFactory {

        @Override
        public Context getInitialContext(Hashtable<?, ?> environment) throws NamingException {
            return new MapBasedContext(environment);
        }
    }

public class MapBasedContext implements Context {
    //actual holder of context
    private static Map values = new ConcurrentHashMap();

    public MapBasedContext() {
    }

    public MapBasedContext(Hashtable<?, ?> environment) {
        values.putAll(environment);
    }

    @Override
    public void bind(String name, Object obj) throws NamingException {
        values.put(name, obj);
    }

    @Override
    public Object lookup(String name) throws NamingException {
        return values.get(name); //you may throw an exception in case if name is absent
    }

    //TODO everything else should be implemented, but actual methods bodies aren't required
}

Answer 3

CDI is the spring "equivalent" in java EE 6
(in fact it is not equivalent cause it covers only Context and DI features, the others one are covered by other JSR implementation like EJB or JPA but if your problem is only to use DI then it will fit perfectly. You won't be able however to use others spring / Java EE features like Container managed transaction for example)
If you want to run it in a standalone application, go on Jboss WELD CDI implementation.

Personally i think that's it's farly better than spring for Context and DI management, but here's not the place to troll