Response + Servlet实现文件下载功能

超、凢脫俗 2022-03-20 05:08 320阅读 0赞

1、获取文件名：request.getParameter()方法

2、获取文件类型名称：getServletContext().getMimeType()方法

3、设置响应文件类型名称（解决文件类型无法识别问题）：response.setContentType()方法

4、设置浏览器以附件形式进行识别（可以实现直接弹窗下载）：response.setHeader("Content-Disposition", "attachment;filename="+文件名);

5、请求参数中文乱码解决(这是由于使用较高版本Tomcat导致):配置tomcat的catalina.properties（最后一行），添加或者修改以下语句：

tomcat.util.http.parser.HttpParser.requestTargetAllow=|{}
    或
    org.apache.tomcat.util.buf.UDecoder.ALLOW_ENCODED_SLASH=true

还有一种解决办法是前台代码使用js提供的encodeURI方法对url进行转义encodeURI（URI）。

还可以在后端对文件名进行编码：

//获取客户信息
    		String agent = request.getHeader("User-Agent");
    		//记录编码之后的名字
    		String filenameEncoder="";
    		if(agent.contains("MSIE")) {
    			//IE浏览器编码
    			filenameEncoder = java.net.URLEncoder.encode(FileName,"UTF-8");
    			filenameEncoder = filenameEncoder.replace("+", " ");
    		}else if(agent.contains("Firefox")) {
    			//火狐浏览器编码
    			BASE64Encoder base64Encoder = new BASE64Encoder();
    			filenameEncoder = "=?UTF-8?B?" + base64Encoder.encode(FileName.getBytes("UTF-8")) + "?=";
    			
    		}else {
    			//基于Chromium内核的浏览器
    			filenameEncoder = java.net.URLEncoder.encode(FileName,"UTF-8");
    		}
    		
    		//设置浏览器以附件形式进行识别(可以实现直接下载相应文件)
    		response.setHeader("Content-Disposition", "attachment;filename="+filenameEncoder);

### 主要代码如下： ###

package com.HttpServlet.Index;
     
    import java.io.FileInputStream;
    import java.io.IOException;
    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.net.URLEncoder.*;
     
    import org.apache.catalina.util.URLEncoder;
     
    import sun.misc.BASE64Encoder;
     
    /**
     * Servlet implementation class DownLoadServlet
     */
    @WebServlet("/DownLoadServlet")
    public class DownLoadServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        /**
         * @see HttpServlet#HttpServlet()
         */
        public DownLoadServlet() {
            super();
            // TODO Auto-generated constructor stub
        }
     
    	/**
    	 * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		response.setContentType("text/html;charset=UTF-8");
    		
    		//获取文件名
    		String FileName = request.getParameter("filename");
    		
    		//把乱码进行转码
    		byte[] bytes = FileName.getBytes("ISO8859-1");
    		FileName = new String(bytes,"UTF-8");
    		//获取文件类型名称
    		String mimeType = this.getServletContext().getMimeType(FileName);
    		//设置响应文件类型名称，这样可以解决文件类型无法识别问题
    		response.setContentType(mimeType);
    		
    		//获取客户信息
    		String agent = request.getHeader("User-Agent");
    		//记录编码之后的名字
    		String filenameEncoder="";
    		if(agent.contains("MSIE")) {
    			//IE浏览器编码
    			filenameEncoder = java.net.URLEncoder.encode(FileName,"UTF-8");
    			filenameEncoder = filenameEncoder.replace("+", " ");
    		}else if(agent.contains("Firefox")) {
    			//火狐浏览器编码
    			BASE64Encoder base64Encoder = new BASE64Encoder();
    			filenameEncoder = "=?UTF-8?B?" + base64Encoder.encode(FileName.getBytes("UTF-8")) + "?=";
    			
    		}else {
    			//基于Chromium内核的浏览器
    			filenameEncoder = java.net.URLEncoder.encode(FileName,"UTF-8");
    		}
    		
    		//设置浏览器以附件形式进行识别(可以实现直接下载相应文件)
    		response.setHeader("Content-Disposition", "attachment;filename="+filenameEncoder);
     
    		//拼接文件路径
    		String FilePath = this.getServletContext().getRealPath("DownLoad/"+FileName);
    		
    		//根绝Path加载文件
    		
    		FileInputStream in = new FileInputStream(FilePath);
    		
    		//获取响应输出流
    		ServletOutputStream out = response.getOutputStream();
    		
    		byte[] buffer = new byte[1024];
    		int length = 0;
    		while( (length = in.read(buffer)) !=-1 ) {
    			out.write(buffer,0,length);
    		}
    		
    		//关闭文件流
    		in.close();
    		out.close();
    	}
     
    	/**
    	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		response.getWriter().append("Served at: ").append(request.getContextPath());
    	}
     
    	/**
    	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		doGet(request, response);
    		
    		String FileName = request.getParameter("filename");
    		System.out.println(FileName);
    		
    	}
     
    }

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="UTF-8">
    <title>首页</title>
    </head>
    <body>
    <hr>
    <h3>下载功能</h3>
    <a href="/JWDemo/DownLoadServlet?filename=宋兆恒.zip">Hern图片</a>
    </body>
    </html>

本文原文地址：[https://blog.csdn.net/qq\_36761831/article/details/86485166][https_blog.csdn.net_qq_36761831_article_details_86485166]

[https_blog.csdn.net_qq_36761831_article_details_86485166]: https://blog.csdn.net/qq_36761831/article/details/86485166