本文讲解如何用java实现把数据库的数据写入到txt中 并实现类似下载软件的样子在网页中弹出下载.

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package datatest;

import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import bean.ConnDB;


public class export extends HttpServlet {
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  //设置编码
  response.setCharacterEncoding("UTF-8");
  //连接数据库
  ConnDB conn = new ConnDB();
  ServletOutputStream outputstream = null;
  BufferedOutputStream buffoutputstream = null; 
  String txt_name = "导出的txt文件名.txt";//导出的txt文件名
  try {
   response.reset();// 清空输出流
   response.setContentType("text/plain;charset=utf-8");
   //设置txt文件名称编码，防止中文乱码
   response.setHeader("Content-disposition", "attachment; filename="+URLEncoder.encode(txt_name, "UTF-8"));
  StringBuffer write = new StringBuffer();
   outputstream=response.getOutputStream();
   buffoutputstream = new BufferedOutputStream(outputstream);
  //根据id查询数据库
   int id=Integer.parseInt(request.getParameter("id"));
   String sql = "select a.id,name,account,password ";
   sql+="from test_rank a ";
   sql+="left join test_join b on b.id=a.id where a.id="+id;
   ResultSet rs = conn.doQuery(sql);
   String content="";
   try {
    while(rs.next())
    {
     //把数据库中读取的数据写入
     content=rs.getString("name")+"\r\n";//在txt中换行为\t\n
     write.append(content);
     content=rs.getString("account")+"\r\n";
     write.append(content);
     break;
    }
   } catch (SQLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
   //write.append(content);
   //设置编码 防止中文乱码
   String str = new String(write.toString().getBytes(),"gbk");
   buffoutputstream.write(str.toString().getBytes("gbk"));
   buffoutputstream.flush();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  finally {
   if (outputstream != null)
    try {
     outputstream.close();
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   if (buffoutputstream != null)
    try {
     buffoutputstream.close();
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
  }

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

}

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