controllerservlet.java

两种开发JSP的模型

package org.sunxin.ch10.model2.servlet;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.sunxin.ch10.model2.beans.UserBean;
import org.sunxin.ch10.model2.beans.UserCheckBean;

public class ControllerServlet extends HttpServlet
{
    public void service(HttpServletRequest request, HttpServletResponse response)
                 throws ServletException,IOException
    {
        request.setCharacterEncoding("GBK");
        response.setContentType("text/html;charset=GBK");
        
        String action=request.getParameter("action");
        
        if (!isValidated(request) && !("login".equals(action)))
        {
            gotoPage("/WEB-INF/pages/login2.jsp",request,response);
            return;
        }
        if("login".equals(action))
        {
            UserBean user=new UserBean();
            user.setName(request.getParameter("name"));
            user.setPassword(request.getParameter("password"));
            
            UserCheckBean uc=new UserCheckBean(user);
                 
            if(uc.validate())
            {
                HttpSession session = request.getSession();
                //将user对象保存到Session对象中，在welcome.jsp中通过
                //<jsp:useBean>动作元素从Session中得到user对象。
                session.setAttribute("user",user);
                //验证成功，将请求转向welcome.jsp。
                gotoPage("/WEB-INF/pages/welcome.jsp", request, response);
            }
            else
            {
                //验证失败，将请求转向loginerr.jsp。
                gotoPage("/WEB-INF/pages/loginerr.jsp", request, response);
            }
        }
        //对于其它的action请求，可在后面的else if...else语句中继续处理。
        /*else if
        {
        }
        else
        {
        }*/
    }
    
    /**
    * 判断用户是否已经登录了。
    */
    private boolean isValidated(HttpServletRequest request)
    {
        HttpSession session = request.getSession();
        if (session.getAttribute("user") != null)
            return true;
        else
            return false;
    }
    
    /**
    * 将请求导向指定的页面。
    */
    private void gotoPage(String targetURL, HttpServletRequest request,
                          HttpServletResponse response)
                   throws IOException, ServletException
    {
        RequestDispatcher rd;
        rd=request.getRequestDispatcher(targetURL);
        rd.forward(request, response);
    }
}