以下是客户端代码
System.setProperty("java.naming.factory.initial", 

"org.jnp.interfaces.NamingContextFactory");
System.setProperty("java.naming.provider.url", 
"localhost:1099");
System.out.println("Step 1");
    try {
     //get naming context
      Context ctx = new InitialContext();
System.out.println("Step 2");
      //look up jndi name
      Object ref = ctx.lookup("hello/Hello");
System.out.println("Step 3");
      //cast to Home interface
      helloHome = (HelloHome) PortableRemoteObject.narrow(ref, 

HelloHome.class);
System.out.println("Step 4");    
  Hello ff=helloHome.create();
System.out.println("Step 5");
      System.out.print(ff.helloWorld()) ;
执行时前四步都没有错误，在第五步creat()出错，提示如下：
Exception in thread "main" java.lang.NoClassDefFoundError: 

org/jboss/security/SecurityAssociation
at 

org.jboss.ejb.plugins.jrmp.interfaces.GenericProxy.getPrincipal(Generic

Proxy.java:184)
at 

org.jboss.ejb.plugins.jrmp.interfaces.HomeProxy.invoke(HomeProxy.java:2

31)
at $Proxy0.create(Unknown Source)
at Client.(Client.java:26)
at Client.main(Client.java:45)
有人知道是怎么回事吗？？

你用下面的试试    
    String url = "localhost:1099";
    String contextFactory="org.jnp.interfaces.NamingContextFactory";
    String urlPkg="org.jboss.naming:org.jnp.interfaces";
    Properties properties = null;
    Context ctx=null;
    try
    {
      properties = new Properties();
      properties.put(Context.INITIAL_CONTEXT_FACTORY, contextFactory);
      properties.put(Context.PROVIDER_URL, url);
      properties.put(Context.URL_PKG_PREFIXES, urlPkg);
      ctx=new InitialContext(properties);
    }
    catch(Exception e)
    {
      System.out.println("...");
      throw e;
    }