Servlet下载方法 Java

来源：互联网发布：巴菲特知乎编辑：程序博客网时间：2024/05/22 09:43

第一步：servlet代码

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;

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

/**
*
* 页面附件下载
* @author sxq
* 只需传入相对的文件路径属性名为：filePath 如filePath=attached/file/20140327/20140327094258_685.xls
*
*/
public class Download extends HttpServlet {
   /**
   *
   */
   private static final long serialVersionUID = -1359970931835765041L;

   private static final String CONTENT_TYPE = "application/octet-stream";

   public void init() throws ServletException {
   }

   /**
   * 页面附件下载
   * 只需传入相对的文件路径属性名为：filePath 如filePath=attached/file/20140327/20140327094258_685_servlet下载.xls
   */
   public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

       response.setContentType(CONTENT_TYPE);//设置内容格式
       String filePathTrue=request.getParameter("filePath");

       if(request.getParameter("filePath").startsWith("/")){
           filePathTrue=filePathTrue.replace(filePathTrue.substring(0,filePathTrue.indexOf("attached")), "");
       }
       String filePath=request.getSession().getServletContext().getRealPath("/")+filePathTrue;

        //判断下载文件是否包含attached文件夹，防止一些非法下载
       if(!filePath.contains("attached")){
           PrintWriter out =response.getWriter();
            out.print("<script>alert('文件路径不合法');</script>");
            out.flush();
            out.close();
           return ;
       }
        //获取文件名
       String filename=filePath.substring(filePath.lastIndexOf("_")+1);
        //创建file对象
        File file=new File(filePath);

        if(!file.exists()){
           PrintWriter out =response.getWriter();
           out.print("<script>alert('文件不存在');</script>");
           out.flush();
           out.close();
           return ;
        }

        //写明要下载的文件的大小
        response.setContentLength((int)file.length());

        //防止中文文件名过长，或者含有“-”字符时，火狐下载，没有文件格式的情况
        if(filename.length()>17){
           filename=filename.substring(0,15)+"..."+filename.substring(filename.lastIndexOf("."));
        }
        if(filename.contains("-")){
           filename=filename.substring(0, filename.indexOf("-")-1)+"..."+filename.substring(filename.lastIndexOf("."));
        }
       //设置附加文件名 ---解决中文乱码
        filename = new String(filename.getBytes("GBK"), "ISO-8859-1");

        response.setHeader("Content-Disposition","attachment;filename="+filename);

        //读出文件到i/o流
        FileInputStream fis=new FileInputStream(file);
        BufferedInputStream buff=new BufferedInputStream(fis);
        byte [] b=new byte[1024];
        long k=0;                               //该值用于计算当前实际下载了多少字节

        OutputStream myout=response.getOutputStream();

        while(k<file.length()){
            int j=buff.read(b,0,1024);
            k+=j;

            myout.write(b,0,j);
        }
        //将写入到客户端的内存的数据,刷新到磁盘
        myout.flush();
        myout.close();
        buff.close();
        fis.close();
   }

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

   }

}

第二步：web.xml 配置

前部分省略，相信一般人看的懂

<servlet>
       <servlet-name>download</servlet-name>
       <servlet-class>servlet文件所在位置</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>download</servlet-name>
       <url-pattern>/download</url-pattern>
   </servlet-mapping>

第三步：访问

很简单的：就可以用html标签直接访问，比如：

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