servlet实现浏览器文件下载

妖狐艹你老母 2022-02-01 07:35 335阅读 0赞

### servlet实现浏览器文件下载 ###

> download.html

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
        <a href="/downloadServlet?filename=01.jpg">点击下载图片</a>
    </body>
    </html>

> DownloadServlet.java

package com.zr.web.servlet;
    
    import com.zr.util.DownLoadUtils;
    
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.ServletOutputStream;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.FileInputStream;
    import java.io.IOException;
    
    @WebServlet("/downloadServlet")
    public class DownloadServlet extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            this.doPost(req, resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            //1.获取请求参数，文件名称
            String filename=req.getParameter("filename");
            //2.使用字节输入流加载文件到内存
            //2.1找到文件服务器路径
            ServletContext servletContext = this.getServletContext();
            String realPath = servletContext.getRealPath("/img/" + filename);
            //2.1用字节流关联
            FileInputStream fis = new FileInputStream(realPath);
    
            //解决中文名乱码问题
            //获取浏览器请求头
            String userAgent = resp.getHeader("user-agent");
            //使用DownLoadUtils工具类方法，处理编码格式
            filename = DownLoadUtils.getFileName(userAgent, filename);
    
            //3.设置response的响应头
            //3.1设置响应头类型：content-type
            String mimeType = servletContext.getMimeType(filename);
            resp.setHeader("content-type",mimeType);
            //3.2设置响应头打开方式：content-disposition
            resp.setHeader("content-disposition","attachment;filename="+filename);
    
            //4.将输入流的数据写出到输出流中
            ServletOutputStream sos = resp.getOutputStream();
            byte[] bytes=new byte[1024*8];
            int len;
            while ((len=fis.read(bytes))!=-1){
                sos.write(bytes,0,len);
            }
        }
    }

> DownLoadUtils.java  
> 工具类

package com.zr.util;
    
    import sun.misc.BASE64Encoder;
    import java.io.UnsupportedEncodingException;
    import java.net.URLEncoder;
    
    /*
        改变文件名编码格式，避免中文乱码
     */
    public class DownLoadUtils {
    
        public static String getFileName(String agent, String filename) throws UnsupportedEncodingException {
            if (agent.contains("MSIE")) {
                // IE浏览器
                filename = URLEncoder.encode(filename, "utf-8");
                filename = filename.replace("+", " ");
            } else if (agent.contains("Firefox")) {
                // 火狐浏览器
                BASE64Encoder base64Encoder = new BASE64Encoder();
                filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
            } else {
                // 其它浏览器
                filename = URLEncoder.encode(filename, "utf-8");
            }
            return filename;
        }
    }

> 01.jpg  
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpYW5ncnVpbHo_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpYW5ncnVpbHo_size_16_color_FFFFFF_t_70]: /images/20220201/e802991879d04a66a7862c0295e1273f.png