Filter-回声对暗号

code.html

    

    
请输入暗号
    暗号1 : 
        
    

err_msg.html

    
暗号输入有误，请重新输入
    

    回到暗号输入界面...
    3后跳转

package filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FilterDemo1 implements Filter {

    /**
     * 在Filter实例创建之后立即执行,进行初始化的操作(里面不写代码也没关系)
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("FilterDemo1实例创建成功");
    }
    /**
     * 对过滤器所拦截的请求，进行处理的核心方法
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        //ServletRequest->HttpServletRequest->xxxRequest
//      HttpServletRequest req=(HttpServletRequest) request;
//      HttpServletResponse res=(HttpServletResponse) response;
//      req.getMethod();
//      res.getContentType();
        //处理...
        System.out.println("FilterDemo1.doFilter()。。。。。");
        //处理请求参数乱码
        request.setCharacterEncoding("utf-8");
        //1.获取用户提交的暗号
        String code1=request.getParameter("code1");
        //2.判断暗号是否正确
        if(!"芝麻开门".equals(code1))
        {
            //3.如果暗号不正确，则跳转到错误提示页面
            request.getRequestDispatcher("/err_msg.html").forward(request, response);
            return;
        }else{
            //4.如果暗号正确，则放行过滤器访问ServletDemo1
            //如果处理OK,要放行过滤器，接着执行后面的资源
            chain.doFilter(request, response);
        }
    }

    /**
     * 在Filter实例销毁之前执行,进行善后的处理(里面不写代码也没关系)
     */
    @Override
    public void destroy() {
        System.out.println("FilterDemo1实例将要被销毁");
    }

}

package filter;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletDemo1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("ServletDemo1.doGet()");
        response.getWriter().write("This is ServletDemo1 !");
        response.getWriter().write("code right!");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

  
    code.html
  
  
   
    listener.MyServletContextListener
    
  
  
    FilterDemo1
    filter.FilterDemo1
  
  
    FilterDemo1
    /ServletDemo1
  
  
    ServletDemo1
    filter.ServletDemo1
  
  
    ServletDemo1
    /ServletDemo1