用Springboot实现文件下载功能

ApiOperation(value = "下载文件", httpMethod = "GET", notes = "downloadFile", response = String.class)
    public String downloadFile(HttpServletRequest request, HttpServletResponse response) {
       String fileName = "zabbix.txt";// 设置文件名
            if (fileName != null) {
                //设置文件路径
               // String realPath = "D://zabbix_agentd.conf";
                String realPath = "D:" + File.separator + "zabbix_agentd.conf";
                File file = new File(realPath , fileName);
                if (file.exists()) {
                    response.setContentType("application/force-download");// 设置强制下载不打开
                    response.addHeader("Content-Disposition", "attachment;fileName=" + fileName);// 设置文件名
                    byte[] buffer = new byte[1024];
                    FileInputStream fis = null;
                    BufferedInputStream bis = null;
                    try {
                        fis = new FileInputStream(file);
                        bis = new BufferedInputStream(fis);
                        OutputStream os = response.getOutputStream();
                        int i = bis.read(buffer);
                        while (i != -1) {
                            os.write(buffer, 0, i);
                            i = bis.read(buffer);
                        }
                        System.out.println("success");
                        
                        InetAddress addr = InetAddress.getLocalHost();  
                        String ip=addr.getHostAddress(); //获取本机ip
                        replacTextContent(ip);
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        if (bis != null) {
                            try {
                                bis.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                        if (fis != null) {
                            try {
                                fis.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
            return null;
    }
    /**
     * 替换文本文件中的 指定字符串
     * @param path
     * @throws IOException
     */
    public void replacTextContent(String ip){
        try {
            File file = new File("D:zabbix_agentd.conf");
            String content = FileUtils.readFileToString(file, "utf-8");
            //原有的内容
            String srcStr = "Hostname=192.168.1.177";        
            //要替换的内容
            String replaceStr ="Hostname"+ ip;     
            // 读  
            FileReader in = new FileReader(content);  
            BufferedReader bufIn = new BufferedReader(in);  
            // 内存流, 作为临时流  
            CharArrayWriter  tempStream = new CharArrayWriter();  
            // 替换  
            String line = null;  
            while ( (line = bufIn.readLine()) != null) {  
                // 替换每行中, 符合条件的字符串  
                line = line.replaceAll(srcStr, replaceStr);  
                // 将该行写入内存  
                tempStream.write(line);  
                // 添加换行符  
                tempStream.append(System.getProperty("line.separator"));  
            }  
            // 关闭 输入流  
            bufIn.close();  
            // 将内存中的流 写入 文件  
            FileWriter out = new FileWriter(file);  
            tempStream.writeTo(out);  
            out.close();  
        }catch (Exception e) {
            e.printStackTrace();
        }
    }