InitialContext.lookup(string) different on Stateless and Stateful session bean

[peter tong]

public class Test1(){
	public vod method1(){
		try{
			Hashtable<String, String> env = new Hashtable<String, String>();
			env.put(Context.INITIAL_CONTEXT_FACTORY, EJB_JNDI_FACTORY);
			env.put(Context.PROVIDER_URL, EJB_URL);
			InitialContext ctx = new InitialContext(env);			
			LogSearchRemote logSearchRemote = (LogSearchRemote) ctx.lookup(LOG_SEARCH_EJB_BINDNAME);
			System.out.println("logSearchRemote = " + logSearchRemote);
			logSearchRemote.setTest(5);
			System.out.println("logSearchRemote.getTest() = " + logSearchRemote.getTest());
			System.out.println("logSearchRemote.getTestAgain() = " + logSearchRemote.getTestAgain());
			LogSearchRemote logSearchRemote2 = (LogSearchRemote) ctx.lookup(LOG_SEARCH_EJB_BINDNAME);
			System.out.println("logSearchRemote2 = " + logSearchRemote2);
			System.out.println("logSearchRemote2.getTest() = " + logSearchRemote2.getTest());
			System.out.println("logSearchRemote2.getTestAgain() = " + logSearchRemote2.getTestAgain());
			this.session = session;
			session.setAttribute("LogSearchEJB", logSearchRemote);
			System.out.println("logSearchRemote = " + logSearchRemote);
		}catch(Exception e){
			e.printStackTrace();
		}
	// if @stateless, throw exception "$Proxy53 cannot be cast to hk.gov.ehr.service.tch.als.admin.logsearch.ejb.LogSearchRemote"
	// if @stateful, no error!!
	LogSearchRemote logSearchRemote = (LogSearchRemote)session.getAttribute("LogSearchEJB");
	//.....
	}
}

1) for the above code, if LogSearchRemote implementation bean is stateful, then

LogSearchRemote logSearchRemote = (LogSearchRemote)session.getAttribute("LogSearchEJB");

has no error, but if LogSearchRemote implementation bean is stateless, then exception
"$Proxy53 cannot be cast to hk.gov.ehr.service.tch.als.admin.logsearch.ejb.LogSearchRemote"
is thrown, why?
2) for stateful session bean, I find each time the

LogSearchRemote logSearchRemote = (LogSearchRemote) ctx.lookup(LOG_SEARCH_EJB_BINDNAME);

return different logSearchRemote implementation bean,
but if stateless session bean, each time the

LogSearchRemote logSearchRemote = (LogSearchRemote) ctx.lookup(LOG_SEARCH_EJB_BINDNAME);

return the same bean!!
why is this case? I expect stateless session bean should not keep state and each lookup should return a different implementation bean.

@Stateless(name = "AlsAdminLogSearch_1_0", mappedName = "ejb/AlsAdminLogSearch_1_0")
public class LogSearchBean implements LogSearchRemote{

	private int test; // kei testing
	
	@Override
	public void setTest(int value){
		test = value;
	}
	
	@Override
	public int getTest(){
		return test;
	}
	
	@Override
	public int getTestAgain(){
		return test;
	}

//...methods

}