将 base64 转为 输入流

                //base64字符串
                String file = "XXXXXXXXXX";
                //将字符串转换为byte数组
                byte[] bytes = new BASE64Decoder().decodeBuffer(file.trim());
                //转化为输入流
                ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes);

ps:要注意向后台传base64字符串时,要去掉   data:image/jpeg;base64,    前缀