string 转换成date
String date="2014-06-26 10:09:22.819"；

SimpleDateFormat sdf = new SimpleDateFormat(

					"yyyy-MM-dd HH:mm:ss.SSS");

Date lastupdated = sdf.parse(date);

	private String changedtos(Date date) {

		// TODO Auto-generated method stub

		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");

		String ss = sdf.format(date);

		System.out.println(ss);

		return ss;

	}

// date以降のmessage

		try {

			Query query = em

					.createQuery(

							"select e from MessageEntity e where e.groupId = :groupId AND :date < e.date"

							+ " order by e.date asc",

							MessageEntity.class);

			query.setParameter("groupId", groupId);

			query.setParameter("date", date);

			return query.getResultList();

		} finally {

			em.close();

		}