spring下载文件

@GetMapping("downloadImg")
public ResponseEntity<byte[]> downloadImg(HttpServletRequest request) {
    String realPath = request.getServletContext().getRealPath("upload/2.jpg");
    byte[] bytes;
    try {
        FileInputStream fileInputStream = new FileInputStream(realPath);
        bytes = new byte[fileInputStream.available()];
        int read = fileInputStream.read(bytes);
    } catch (IOException e) {
        throw new RuntimeException(e);
    }
    //告知浏览器，我的流是一个 附件 （文件），浏览器触发下载
    HttpHeaders httpHeaders = new HttpHeaders();
    String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
    System.out.println(fileName);
    httpHeaders.setContentDispositionFormData("attachment", fileName);
    //返回对象
    ResponseEntity<byte[]> responseEntity = new ResponseEntity<>(bytes, httpHeaders, HttpStatus.OK);
    return responseEntity;
}

乱码解决：获取文件名的时候，将文件名转为utf-8格式：

String encode = URLEncoder.encode(fileName, "UTF-8");

下载rar文件如下：

@GetMapping("downLoadTxt")
    public ResponseEntity<byte[]> downLoadTxt(HttpServletRequest request){
        //获取要下载的文件地址
        String realPath = request.getServletContext().getRealPath("upload/新建文本文档.txt");
        byte[] bytes;
        String fileName;
        try {
            //将文件转为字节流对象
            FileInputStream fileInputStream = new FileInputStream(realPath);
            //定义接收字节流对象的数组
            bytes = new byte[fileInputStream.available()];
            //读取字节流
            int read = fileInputStream.read(bytes);
            //获取文件名并且将文件名编码格式改为utf-8
            fileName = URLEncoder.encode(realPath.substring(realPath.lastIndexOf("\\")+1),"UTF-8");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        //告诉浏览器，出发下载
        HttpHeaders httpHeaders = new HttpHeaders();
        //设置浏览器下载附件，传入文件名
        httpHeaders.setContentDispositionFormData("attachment",fileName);
        //返回响应实体，字节流数组，下载附件，状态
        return new ResponseEntity<byte[]>(bytes,httpHeaders,HttpStatus.OK);
    }