loginfilter.java

一些的javaee5的实用代码

package ch10;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class LoginFilter extends HttpServlet implements Filter {
    private FilterConfig filterConfig;
    //Handle the passed-in FilterConfig
    public void init(FilterConfig filterConfig) {
        this.filterConfig = filterConfig;
    }
    //Process the request/response pair
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) {
        String username = request.getParameter("username");
        String userpass = request.getParameter("userpass");
        if(username.length()==0&&userpass.length()==0)
        {
            response.setContentType("text/html;charset=gb2312");
            try
            {
                PrintWriter out = response.getWriter();
                out.print("用户名和口令均为空，请重新输入！");
                out.flush();
                return;
            }catch(Exception e){}
        }
        try {
            filterChain.doFilter(request, response);
        }
        catch(ServletException sx) {
            filterConfig.getServletContext().log(sx.getMessage());
        }
        catch(IOException iox) {
            filterConfig.getServletContext().log(iox.getMessage());
        }
    }
    //Clean up resources
    public void destroy() {
    }
}