Java base64 添加data URI

　　任何语言生成的base64均不会携带data URI，而前端在读取base64时需要携带data URI头

    public String getContentType(Path path){
        try {
            return Files.probeContentType(path);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    public String getContentType(byte[] bytes){
        MagicMatch match = null;
        try {
            match = Magic.getMagicMatch(bytes);
        } catch (MagicParseException e) {
            e.printStackTrace();
        } catch (MagicMatchNotFoundException e) {
            e.printStackTrace();
        } catch (MagicException e) {
            e.printStackTrace();
        }
        return match.getMimeType();
    }

    public String encryptToBase64(String filePath) {
        if (filePath == null) {
            return null;
        }
        try {
            Path path = Paths.get(filePath);
            if(Files.exists(path,new LinkOption[]{ LinkOption.NOFOLLOW_LINKS})){
                byte[] b = Files.readAllBytes(path);
                String contentType = getContentType(path);
                String contentType1 = getContentType(b);
                String base64str1 = DatatypeConverter.printBase64Binary(b);  //Java7
                String base64Str = Base64.getEncoder().encodeToString(b);
                // cretate "data URI"
                StringBuilder sb = new StringBuilder();
                sb.append("data:");
                sb.append(contentType);
                sb.append(";base64,");
                sb.append(base64Str);
                return sb.toString();
            }
            return null;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }