java下载文件，返回文件流

有时候我们会下载服务器文件，需要将文件返回：

/** * 文件下载 * * @param fileName * @param request * @param response * @throws Exception * @PathVariable注解参考https://www.cnblogs.com/williamjie/p/9139548.html */
    @ApiOperation("文件下载")
    @PostMapping("/download/{fileName}.log")
    public void download(@PathVariable("fileName") String fileName, HttpServletRequest request, HttpServletResponse response) throws Exception { 
   
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("UTF-8");
        //fileName为传入的要下载的文件的文件名，本示例下载的是日志文件所以后缀是.log
        fileName = URLDecoder.decode(fileName, "UTF-8");
        //要下载的文件的路径
        File logFile = new File("/usr/local/jar/log/" + fileName + ".log");
        try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(logFile));
             BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream())) { 
   
            long fileLength = logFile.length();
            response.setContentType("application/x-msdownload;");
            response.setHeader("Content-disposition", "attachment; filename=" + new String(fileName.getBytes("utf-8"), "ISO8859-1"));
            response.setHeader("Content-Length", String.valueOf(fileLength));
            byte[] buff = new byte[2048];
            int bytesRead;
            while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) { 
   
                bos.write(buff, 0, bytesRead);
            }
        } catch (Exception e) { 
   
            logger.error("错误信息: ", e);
        }
    }

如果使用commons上面代码可简化代码如下：
org.apache.commons.io的maven如下：

<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.11.0</version>
</dependency>

简化代码：

    /** * 文件下载 * * @param fileName * @param request * @param response * @throws Exception * @PathVariable注解参考https://www.cnblogs.com/williamjie/p/9139548.html */
    @ApiOperation("文件下载")
    @PostMapping("/download/{fileName}.log")
    public void download(@PathVariable("fileName") String fileName, HttpServletRequest request, HttpServletResponse response) throws Exception { 
   
        //fileName为传入的要下载的文件的文件名，本示例下载的是日志文件所以后缀是.log
        fileName = URLDecoder.decode(fileName, "UTF-8");
        //要下载的文件的路径
        File logFile = new File("/usr/local/jar/log/" + fileName + ".log");
        InputStream in = new FileInputStream(logFile);
        String filenamedisplay = URLEncoder.encode(fileName + ".log", "UTF-8");
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("UTF-8");
        response.setHeader("Content-Disposition", "attachment; filename=" + filenamedisplay);
        response.setContentType("application/x-download;charset=utf-8");
        OutputStream out = response.getOutputStream();
        IOUtils.copy(in, out);
        out.flush();
        in.close();
    }