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();
		}