下载大文件时内存溢出怎么解决？？

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报错：java.lang.OutOfMemoryError: Java heap space

  @RequestMapping("/download")
  public void download (HttpServletResponse res,@Param("url")String url) throws IOException{
      byte[] retArr = null; 
      String fileName = new String(url.getBytes(),"ISO-8859-1");
      String path = request.getSession().getServletContext().getRealPath("vod"+File.separator+"log"+File.separator+url); 

          try {  
              File file = new File(path);  
              FileInputStream fis = new FileInputStream(file);  
              ByteArrayOutputStream bos = new ByteArrayOutputStream(1000);  
              byte[] b = new byte[1000];  
              int n;  
              while ((n = fis.read(b)) != -1) {  
                  bos.write(b, 0, n);  
              }  
              fis.close();  
              bos.close();  
              retArr = bos.toByteArray();  
          } catch (FileNotFoundException e) {  
              e.printStackTrace();  
          } catch (IOException e) {  
              e.printStackTrace();  
          }  
      OutputStream os = res.getOutputStream();  
      try {  
          res.reset();  
          res.setHeader("Content-Disposition", "attachment; filename="+fileName);  
          res.setContentType("application/octet-stream; charset=utf-8");  
          os.write(retArr);  
          os.flush();  
      } finally {  
          if (os != null) {  
              os.close();  
          }  
      }  
  }