利用J2EE模式构建网站

   public void performTask(javax.servlet.http.HttpServletRequest request,
  javax.servlet.http.HttpServletResponse response)
  throws javax.servlet.ServletException, java.io.IOException 
   {
       RegisterHelper rh=new RegisterHelper(request,response);//启动注册视图助手
       Command command=rh.getCommand();//由视图助手中获得并初始化Command
       CustomerBean cb=rh.getCustomerBean();//由视图助手中获得并初始化值对象
       request.setAttribute("customerbean",cb);
       String dispatcher=rh.getDispatcher();//由视图助手中获得并初始化分发者
    request.setAttribute("type",rh.getType());//设置上下文属性
       try {
        command.execute((Helper)rh);//执行业务代码
       } catch(javax.ejb.DuplicateKeyException de) {
  request.setAttribute("errorbean",new ErrorBean("对不起，已经有人注册了该用户名!"));//注册重名处理
  dispatch(request,response,dispatcher);//分发并移交控制权
  return;
       } catch(Exception e) {
     request.setAttribute("errorbean",new ErrorBean("对不起，数据库出错!"));//出错处理
  dispatch(request,response,dispatcher);
  return;
    }
       dispatch(request,response,dispatcher);
    
   }
   
    

public class RegisterHelper implements Helper {
 static String dispatcher = "RegisterDispatcher";
 private CustomerBean customer = null;
 private String type = null;
 
 public RegisterHelper(
  javax.servlet.http.HttpServletRequest request,
  javax.servlet.http.HttpServletResponse response) {
  setType(request);
  setCustomerBean(request);  
 }
 /**
  * 定义页面类型:HTML or XML
  */
 public void setType(javax.servlet.http.HttpServletRequest request) {
  type = request.getParameter("type");
 }
 /**
  * 获取Command
  */
 public Command getCommand() {
  RegisterCommand rc = new RegisterCommand();
  return rc;
 }
 /**
  * 向值对象中填充数据
  */
 public void setCustomerBean(javax.servlet.http.HttpServletRequest request) {
  customer = new CustomerBean();
  customer.setUsername(request.getParameter("username"));
  customer.setPassword(request.getParameter("password"));
  customer.setEmail(request.getParameter("email"));
  customer.setTruename(request.getParameter("truename"));
  customer.setId(request.getParameter("id"));
  customer.setService(this.setService(request));
 }
 /**
  * 获取值对象
  */
 public CustomerBean getCustomerBean() {
  return this.customer;
 }
 /**
  * 获取分发者
  */
 public String getDispatcher() {
  return this.dispatcher;
 }
 /**
  * 获取类型
  */
 public String getType() {
  return type;
 }
}
    

      public void execute(Helper helper) throws Exception 
   {
      RegisterHelper rh = (RegisterHelper) helper;//获取视图助手
  CustomerBean cb = rh.getCustomerBean();//从视图助手中获取值对象
  ServiceLocator sl = ServiceLocator.getInstance();//初始化服务定位器
  CustomersHome ch = (CustomersHome) sl.getHome(ServiceLocator.Services.CUSTOMERS);//从服务定位器中获取Entity Bean本地接口
  try { 
   Customers customers = ch.create(cb);//将注册信息导入数据库
  } catch(javax.ejb.DuplicateKeyException e) {
   throw new javax.ejb.DuplicateKeyException();
  } catch(Exception e) {
   throw e;
  }
 
   }
   
    

  public void performTask(
  javax.servlet.http.HttpServletRequest request,
  javax.servlet.http.HttpServletResponse response)
  throws javax.servlet.ServletException, java.io.IOException {
  String type=(String)request.getAttribute("type");//获取页面类型
  isError=(request.getAttribute("errorbean")!=null)?true:false;//判断是否出错
  String file=selectType(type,isError,response);//根据页面类型和是否出错确定显示页面
  getServletConfig().getServletContext().getRequestDispatcher(file).forward(request,response);//重定向到显示页面
 }
 
 public String selectType(String str,boolean isError,javax.servlet.http.HttpServletResponse response) {
  if (str.equals("html")) {//HTML类型的页面
   if (isError) {//成功
    System.out.println("Some error happens!");
    return "register_error.jsp";
   } else {//出错    return "register_ok.jsp";
   }
  } else {//WML手机页面
   if (isError) {//成功
    System.out.println("Some error happens!");
    return "wml/register_error.jsp";
   } else {//出错    
    response.setContentType("text/vnd.wap.wmlcharset=ISO-8859-1");
    return "wml/register_ok.jsp";
   }
  }
 }
 
    

public class ServiceLocator 
{
    private static ServiceLocator me;
 InitialContext context = null;
   /**
    * 初始化上下文
    */
   public ServiceLocator() 
   {
  try {
   context = new InitialContext();
  } catch (NamingException e) {
   e.printStackTrace();
  }    
   }
 public class Services {
  //为EJB设定请求序号
  final public static int CUSTOMERS=0;
  final public static int PARTNERS=1;
  final public static int ADMINISTRATORS=2;
  final public static int PERMITS=3;
  final public static int PAPERBROKER=4;
  final public static int CHECK=5;
 }
 final static Class CUSTOMERS_CLASS=CustomersHome.class;
 final static String CUSTOMERS_NAME="CustomersHome";
 final static Class PARTNERS_CLASS=PartnersHome.class;
 final static String PARTNERS_NAME="PartnersHome";
 final static Class ADMINISTRATORS_CLASS=AdministratorsHome.class;
 final static String ADMINISTRATORS_NAME="AdministratorsHome";
 final static Class PERMITS_CLASS=PermitsHome.class;
 final static String PERMITS_NAME="PermitsHome";
 final static Class PAPERBROKER_CLASS=PaperBrokerHome.class;
 final static String PAPERBROKER_NAME="PaperBrokerHome";
 final static Class CHECK_CLASS=CheckHome.class;
 final static String CHECK_NAME="CheckHome";
 public static ServiceLocator getInstance() {//单线程处理以节省资源
  if (me == null)
   me = new ServiceLocator();
  return me;
 }   
 static private Class getServiceClass(int service) {
  switch(service) {
   case Services.CUSTOMERS:
    return CUSTOMERS_CLASS;
   case Services.PARTNERS:
    return PARTNERS_CLASS;
   case Services.ADMINISTRATORS:
    return ADMINISTRATORS_CLASS;
   case Services.PERMITS:
    return PERMITS_CLASS;
   case Services.PAPERBROKER:
    return PAPERBROKER_CLASS;
   case Services.CHECK:
    return CHECK_CLASS;
  }
  return null;
 }
 static private String getServiceName(int service) {
  switch(service) {
   case Services.CUSTOMERS:
    return CUSTOMERS_NAME;
   case Services.PARTNERS:
    return PARTNERS_NAME;
   case Services.ADMINISTRATORS:
    return ADMINISTRATORS_NAME;
   case Services.PERMITS:
    return PERMITS_NAME;
   case Services.PAPERBROKER:
    return PAPERBROKER_NAME;
   case Services.CHECK:
    return CHECK_NAME;
  }
  return null;
 }
   /**
    * 返回EJB本地接口
    */
   public EJBHome getHome(int s) 
   {
     EJBHome home = null;
  try {
   Object objref = context.lookup(getServiceName(s));
   home = (EJBHome) PortableRemoteObject.narrow(objref, getServiceClass(s));
  } catch (NamingException e) {
   e.printStackTrace();
  }
  return home;
   }
}