Java代码

import java.io.IOException;import java.io.InputStream;import java.util.Properties;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class DownServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {        //获取表单参数        String username = request.getParameter("username");        String password = request.getParameter("password");        //用户名和密码是否填了        if(username!=null && password!=null){            //加载文件            InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/cn/itcast/web/request/config.properties");            Properties props = new Properties();            props.load(is);            //请求参数与文件内容是否相同            if(props.getProperty(username).equals(password)){                //有权限                response.setHeader("content-disposition","attachment;filename=a.JPG");            }else{                //转发到message.html页面                request                    .getRequestDispatcher("/message.html")                    .forward(request,response);            }        }else{            //转发到login.html页面            request                .getRequestDispatcher("/login.html")                .forward(request,response);        }    }    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {        request.setCharacterEncoding("UTF-8");        this.doGet(request,response);    }}

config.properties
uername=liwen
password=123456

html代码

index.html

HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">                    

HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">