本文实例为大家分享了servlet下载文件的具体代码，供大家参考，具体内容如下

1.servlet下载文件

　　servlet下载文件就是将服务器端的文件传输到客户端。

2案例

下载文件servlet类

package com.learn;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;/** * Created by Administrator on 2017/09/24. */public class DownLoadServlet extends HttpServlet { private String filePath; @Override public void init(ServletConfig config) throws ServletException { super.init(config); filePath = config.getInitParameter("filePath"); //初始化路径 //filePath = config.getServletContext().getRealPath(filePath); System.out.println("初始化文件路径："+filePath); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req,resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { OutputStream out; //输出流 InputStream in; //输入流 String fileName = req.getParameter("fileName"); System.out.println("文件名称："+fileName); //如果把文件名为null则提示用户 if(fileName == null){ out = resp.getOutputStream(); out.write("please input fileName".getBytes()); out.close(); } //获取文件流 in = getServletContext().getResourceAsStream(filePath+ File.separator+fileName); System.out.println(in==null?true:false); int length = in.available(); //设置返回消息头部信息 resp.setContentType("application/force-download"); resp.setHeader("Content-Length",String.valueOf(length)); resp.setHeader("content-disposition","attachment;filename=\""+fileName+"\""); //输出文件到客户端 out = resp.getOutputStream(); int bytesend = 0 ; byte[] buff = new byte[512]; while ((bytesend = in.read(buff))!= -1){ out.write(buff,0,bytesend); } in.close(); out.close(); }}

web.xml配置

<servlet> <servlet-name>download</servlet-name> <servlet-class>com.learn.DownLoadServlet</servlet-class> <init-param> <param-name>filePath</param-name> <param-value>file</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>download</servlet-name> <url-pattern>/download</url-pattern> </servlet-mapping>