@IocBean(name = "emailService")
public class EmailService {
	private static final Log log = Logs.get();

	@Inject("refer:$ioc")
	protected Ioc ioc;

	public boolean send(String to, String subject, String html) {
		try {
			HtmlEmail email = ioc.get(HtmlEmail.class);
			email.setSubject(subject);
			email.setHtmlMsg(html);
			email.addTo(to);
			email.buildMimeMessage();
			email.sendMimeMessage();
			return true;
		} catch (Throwable e) {
			log.info("send email fail", e);
			return false;
		}
	}
}

这代码里面的HtmlEmail是什么时候注入的？，这代码在入门手册里面有的！表示不懂什么时候就注入了，哪里写了相关的注入？