我需要在springboot中的组件之间创建一条消息。为此，我创建了一个messagehandler组件，需要使用一个键并清除输出消息，因为它具有单例作用域。
我不知道这是不是最好的办法。有什么建议吗？

@Component
public class MessageHandler {
    @Autowired
    private JavaMailSender emailSender;
    Map<String, StringBuilder> outputMessage = new HashMap<String, StringBuilder>();
    public void addMessage(@NotNull String key, @NotNull String str) {
        if (key != null && !key.isEmpty() && str != null && !str.isEmpty()) {
            if (outputMessage.containsKey(key)) {
                outputMessage.put(key, outputMessage.get(key).append(str + "\n"));
            } else {
                outputMessage.put(key, new StringBuilder(str + "\n"));
            }
        }
    }
    public String getMessage(@NotNull String key) {
        if (key != null && !key.isEmpty())
            return outputMessage.get(key).toString();
        return "";
    }
    public void clear(@NotNull String key) {
        outputMessage.remove(key);
    }
    public void sendStringAsAttachment(String to, String subject, String text, String filename) {
        MimeMessage message = emailSender.createMimeMessage();
        try {
            MimeMessageHelper helper = new MimeMessageHelper(message, true);
            helper.setTo(to);
            helper.setSubject(subject);
            helper.setText(text);
            byte[] bytes = getMessage(filename).getBytes(Charset.forName("UTF-8"));
            helper.addAttachment(filename, new ByteArrayResource(bytes));
        } catch (MessagingException ex) {
            logger.error("Could not send file {}", ex.getMessage());
        }
        emailSender.send(message);
    }
}