1.读文件

package com.demo;import java.io.BufferedReader;import java.io.FileReader;import java.io.PrintWriter;import javax.servlet.http.*;public class ServletFileTest1 extends HttpServlet {    public void doGet(HttpServletRequest req,HttpServletResponse res){        try {            req.setCharacterEncoding("gb2312");            res.setContentType("text/html;charset=gb2312");            PrintWriter pw=res.getWriter();//创建一个FileReader            FileReader f=new FileReader("D:\\myCount.txt");            BufferedReader br=new BufferedReader(f);            String numVal=br.readLine();            br.close();     //一定要关闭文件流            pw.println("从文件中读取的数据是： "+numVal);        } catch (Exception e) {            e.printStackTrace();        }    }        public void doPost(HttpServletRequest req,HttpServletResponse res){        this.doGet(req, res);    }}

2.写文件

package com.demo;import java.io.*;import javax.servlet.http.*;public class ServletFileTest2 extends HttpServlet{    public void doGet(HttpServletRequest req,HttpServletResponse res){        try {            req.setCharacterEncoding("gb2312");            res.setContentType("text/html;charset=gb2312");            PrintWriter pw=res.getWriter();//创建一个FileWriter            FileWriter f=new FileWriter("D:\\myCount.txt");            BufferedWriter bw=new BufferedWriter(f);            bw.write("hello");    //会把原来文件中的信息给删除掉，相当于>            bw.close();            pw.println("向文件写入信息");        } catch (Exception e) {            e.printStackTrace();        }    }    public void dopost(HttpServletRequest req,HttpServletResponse res){        this.doGet(req, res);    }}