Question

in my application the follwoing code is used. Can some one give a detailed explanation for the code that is highlighted?

I understood that in first highlighted block java reflection is used in invoking the method handle_validation..but need the detailed explanation.

Then in second highlighted block RemoteException is thrown..

My exact question is why they used reflection to call EngineHandlerIF and then why they are using RMI in this EngineHandlerIF to invoke the definition of method in EngineHandler?

private static EngineHandlerIF init() {
        ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[] { "validation.xml" });
        String[] beans = ctx.getBeanDefinitionNames();
        for (String string : beans) {
            logger.info(string);
        }
        EngineHandlerIF engine = (EngineHandlerIF) ctx.getBean("engine");
        return engine;
    }



private Object callEngineMethod(MiddlewareMessage mmsg) {
        Object resultObj;
        try {
            **String methodName = "handle_validation";
            Method method = EngineHandlerIF.class.getDeclaredMethod(methodName, MiddlewareMessage.class);
            method.setAccessible(true);
            resultObj = method.invoke(engine, new Object[] { mmsg });**
        } catch (Exception e) {
            logger.error("sendMessage Exception: ", e);
            return new Boolean(false);
        }
        return resultObj;
    }

EngineHandlerIF:
----------------
**public abstract String handle_validation(MiddlewareMessage mmsg) throws RemoteException;**

EngineHandler:
--------------
public String handle_validation(MiddlewareMessage mmsg) throws Exception {
//some code
    }

Answer 1

I understood that in first highlighted block java reflection is used
in invoking the method handle_validation..but need the detailed
explanation.

That’s pretty much it. The only other bit is the

 method.setAccessible(true);

which makes the method accessible to the caller (e.g. from private to public), thus allowing you to call it. However the above method does appear to be public already. Perhaps this is some legacy following a refactor ?

Note that this isn’t RMI (remote method invocation), but rather reflection. The only RMI I can see here is the handle_validation() method possibly throwing a RemoteException.