import java.lang.reflect.*;
import java.rmi.*;
import javax.ejb.*;
import javax.naming.*;

import com.gdpost.isp.lis.util.exception.*;
import com.gdpost.isp.lis.util.logging.*;
import com.gdpost.isp.lis.util.naming.*;

/**
 * <p>Title: stateless sessionBean的动态代理。这是一个单实例类，
 * 只能通过getInstance方法获得这个实例。</p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: </p>
 * @author wuwei
 * @version 1.0
 */
public class DynamicEJBProxy {

    // 私有构造函数，防止从外部创建实例
    private DynamicEJBProxy () {}

    private static DynamicEJBProxy singleton = new DynamicEJBProxy ();
    /**
     * 得到唯一的实例
     * @return  本类唯一的一个实例
     */
    public static DynamicEJBProxy getInstance () {
        return singleton;
    }

    /**
     * 此方法用来呼叫指定的stateless sessionBean的指定的业务方法。
     * 实现过程为：
     *   <br>&nbsp;&nbsp;1>  根据jndiName和homeInterface找到home接口
     *   <br>&nbsp;&nbsp;2>  呼叫home接口的create方法，返回remote接口
     *   <br>&nbsp;&nbsp;3>  呼叫remote接口的业务方法，保存调用结果
     *   <br>&nbsp;&nbsp;4>  呼叫remote接口的remove方法
     *   <br>&nbsp;&nbsp;5>  返回第3步的调用接过
     * @param jndiName  sessionBean的JNDI名字
     * @param homeInterface  sessionBean的home接口类型
     * @param methodName  sessionBean的业务方法名字
     * @param args  sessionBean的业务方法参数
     * @return  sessionBean的业务方法返回结果
     * @throws UserException  被呼叫的sessionBean的业务方法抛出的业务异常
     */
    public Object invoke (String jndiName,
                          Class homeInterface,
                          String methodName,
                          Object[] args)
        throws UserException {
        try {
            // 得到home stub
            EJBHome homestub =
                NamingLocator.getInstance().lookup (
                jndiName, homeInterface);

            // 调用home stub上的create方法，得到remote stub
            Object remotestub = homestub.getClass ().getMethod (
                "create", null).invoke (homestub, null);

            // 得到remote stub上的要调用的业务方法的参数类型
            Class[] paramTypes = new Class[args.length];
            for (int i = 0; i < args.length; ++i) {
                paramTypes[i] = args[i].getClass ();
            }

            // 调用remote stub上的业务方法
            Object returnValue = remotestub.getClass ().getMethod (
                methodName, paramTypes).invoke (remotestub, args);

            // 调用remote stub上的remove方法
            remotestub.getClass ().getMethod (
                "remove", null).invoke (remotestub, null);

            // 返回调用结果
            return returnValue;
        }
        catch (NamingException e) {
            LoggingUtil.loggingExceptionInLIS (e);
            throw new UserException ("399490000", 3, 6, "", "查询jndi出现异常");
        }
        catch (NoSuchMethodException e) {
            LoggingUtil.loggingExceptionInLIS (e);
            throw new UserException ("399490000", 3, 6, "", "ejb没有"+methodName+"方法");
        }
        catch (IllegalAccessException e) {
            LoggingUtil.loggingExceptionInLIS (e);
            throw new UserException ("399490000", 3, 6, "", e.getMessage());
        }
        catch (InvocationTargetException e) {
            // 得到sessionBean的create方法、业务方法以及remove方法抛出的异常
            Throwable cause = e.getTargetException();
            LoggingUtil.loggingExceptionInLIS (cause);
            // 判断异常的类型
            if (cause instanceof CreateException) {
                throw new UserException ("399490000", 3, 6, "",
                                         "ejb抛出CreateException");
            }
            else if (cause instanceof RemoveException) {
                throw new UserException ("399490000", 3, 6, "",
                                         "ejb抛出RemoveException");
            }
            else if (cause instanceof RemoteException) {
                throw new UserException ("399490000", 3, 6, "",
                                         "ejb抛出RemoteException");
            }
            else if (cause instanceof UserException) {
                // 真正的业务异常
                throw (UserException) cause;
            }
            else {
                // 未知类型的异常
                throw new UserException ("399490000", 3, 6, "",
                                         "ejb抛出未知类型的异常");
            }
        }
    }

}

import javax.naming.*;
import java.util.Properties;
import javax.rmi.PortableRemoteObject;
import javax.ejb.*;
import java.lang.reflect.*;
...
...

class EJBInvocationHandler implements InvocationHandler {
  private Object homeStub;
  public EJBInvocationHandler(Object o) {
    homeStub = o;
  }
  public Object invoke(Object proxy,Method method,Object[] args){
    Object returnValue = null;
    Class[] argTypes = null;
    try {
      Object remoteStub = homeStub.getClass().getMethod("create",
          null).invoke(homeStub, null);
      // 得到remote stub上的要调用的业务方法的参数类型
      if(args != null){
        argTypes = new Class[args.length];
        for (int i = 0; i < args.length; i++) {
          argTypes[i] = args[i].getClass();
        }
      }
      // 这里可以加入诸如权限控制和日志记录的代码
      ...
      ...
      // 调用remote stub上的业务方法
      returnValue = remoteStub.getClass().getMethod(method.getName(),
          argTypes).
          invoke(remoteStub, args);
      // 调用remote stub上的remove方法
      remoteStub.getClass().getMethod("remove", null).invoke(remoteStub, null);
    }
    catch (Exception e) {
      e.printStackTrace();
    }
    return returnValue;
  }
}

public class DynamicEJBProxy{
  private Context ctx;
  public DynamicEJBProxy() {
    try{
      //create initial context
      String url = "t3://127.0.0.1:7001";
      String user = null;
      String password = null;

      Properties h = new Properties();
      h.put(Context.INITIAL_CONTEXT_FACTORY,
            "weblogic.jndi.WLInitialContextFactory");
      h.put(Context.PROVIDER_URL, url);
      ctx = new InitialContext(h);
    }
    catch(NamingException e){
      System.out.print(e.getMessage());
    }
  }
  private static DynamicEJBProxy me = new DynamicEJBProxy();
  static public DynamicEJBProxy getInstance() {
    return me;
  }
  public Object createProxy(String jndi,Class clazz){
    Object proxy = null;
    try {
      //look-up home
      Object home = ctx.lookup(jndi);
      Object homeStub = PortableRemoteObject.narrow(home, home.getClass());
      ClassLoader loader = clazz.getClassLoader();

      EJBInvocationHandler handler = new EJBInvocationHandler(homeStub);
      //创建homeStub的动态代理类
      proxy = Proxy.newProxyInstance(loader, new Class[] {clazz},handler);
    }
    catch(Exception e){
      System.out.print(e.getMessage());
    }
    return proxy;
  }
  
  //调用方式
  //SessionFacadeInterface是Web与Session Bean的通用接口
  //JbPurviewManagerFacade是Session Bean的JNDI名
  public static void main(String[] args){
    try{
      DynamicEJBProxy proxyManager = DynamicEJBProxy.getInstance();
      SessionFacadeInterface proxy = (SessionFacadeInterface) proxyManager.createProxy("JbPurviewManagerFacade",SessionFacadeInterface.class);

      //通过Web与Session Bean的通用接口调用业务方法

      JbUserDto[] users = (JbUserDto[]) proxy.getAllUsers();
      ...
      ...
    }
    catch(Exception e){
      System.out.print(e.getMessage());
    }
  }
}