java: read image file from resou

pre

public Boolean uploadAvatarByDefaultImage(AccountEntity user) {
        ResponseBody responseInfo = null;
        try {
            String index=user.getExtensionLink()[0].getExtension().substring(2);
            File photo = new File("./avatar/"+index+".png");
            String name = "image";
            String fileName = "user_avatar.png";
            String mediaType = "image/png";
            BufferedImage bufferedImage = ImageIO.read(photo);
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ImageIO.write(bufferedImage, "png", bos);
            byte[] fileContent = bos.toByteArray();
            ## responseInfo = setting avatar function ##
            return responseInfo.contentLength() == (-1);

        } catch (NoSuchFileException e) {
            logger.error("not avatar file", e);
        } catch (IOException | RestException e) {
            logger.error("failed to upload avatar", e);
        } finally {
            if (responseInfo != null) {
                responseInfo.close();
            }
        }
        return false;
    }

很早以前实现的一个用来更新账号头像的方法，当时没有注意在docker跑的时候会失败
问题点在于以前是直接去load一个文件，但是在docker跑的时候，已经打包成一个jar包，直接load是没办法去获取的
把图片文件放在resources目录下，就可以使用java的load resources的方法去读取文件
网上给的方法是

1. BufferedImage im = ImageIO.read(new File(getClass().getResource(fileName).toURI()));
这种方法没办法读取到文件
2. BufferedImage buff =ImageIO.read(getClass().getResourceAsStream(fileName));
这种方法是OK的

也可以使用java封装好的类ClassPathResource

ClassPathResource resource = new ClassPathResource(pngPath);

filePath: /avatar 即可

after

public Boolean uploadAvatarByDefaultImage(AccountEntity user) {
        ResponseBody responseInfo = null;
        try {
            String index=user.getExtensionLink()[0].getExtension().substring(2);
            String name = "image";
            String fileName = "user_avatar.png";
            String mediaType = "image/png";
            String pngPath = "/avatar/" + index + ".png"; 
            ClassPathResource resource = new ClassPathResource(pngPath);
            BufferedImage bufferedImage = ImageIO.read(resource.getInputStream());
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ImageIO.write(bufferedImage, "png", bos);
            byte[] fileContent = bos.toByteArray();
           ## responseInfo = setting avatar function ##
            bos.close(); #只要是stream类型都需要close
            return responseInfo.contentLength() == (-1);

        } catch (NoSuchFileException e) {
            logger.error("not avatar file", e);
        } catch (IOException | RestException e) {
            logger.error("failed to upload avatar", e);
        } finally {
            if (responseInfo != null) {
                responseInfo.close();
            }
        }
        return false;
    }