java.lang.OutOfMemoryError Java heap space

public static String uploadSingleFile(String path,MultipartFile file) {
   
  if (!file.isEmpty()) {
     
      byte[] bytes;
      try {
        bytes = file.getBytes();
         
        // Create the file on server
        File serverFile = createServerFile(path,file.getOriginalFilename());
        BufferedOutputStream stream = new BufferedOutputStream(
            new FileOutputStream(serverFile));
        stream.write(bytes);
        stream.flush();
        stream.close();
 
        logger.info("Server File Location="
            + serverFile.getAbsolutePath());
 
        return getRelativePathFromUploadDir(serverFile).replaceAll("\\\\", "/");
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        System.out.println(e.getMessage());
      }
     
  }else{
    System.out.println("文件内容为空");
  }
  return null;  
}

public static String uploadSingleFile(String path,MultipartFile file) {
   
  if (!file.isEmpty()) {
     
      //byte[] bytes;
      try {
        //bytes = file.getBytes();
         
        // Create the file on server
        File serverFile = createServerFile(path,file.getOriginalFilename());
        BufferedOutputStream stream = new BufferedOutputStream(
            new FileOutputStream(serverFile));
        int length=0;
        byte[] buffer = new byte[1024];
        InputStream inputStream = file.getInputStream();
        while ((length = inputStream.read(buffer)) != -1) {
          stream.write(buffer, 0, length);
        }
        //stream.write(bytes);
        stream.flush();
        stream.close();
 
        logger.info("Server File Location="
            + serverFile.getAbsolutePath());
 
        return getRelativePathFromUploadDir(serverFile).replaceAll("\\\\", "/");
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        System.out.println(e.getMessage());
      }
     
  }else{
    System.out.println("文件内容为空");
  }
  return null;  
}