code: private static String getIdentitiesFromCertficate(X509Certificate aCert) {
  		String tDN = aCert.getSubjectDN().toString(); 
  		String tPart = "";
  		if ((tDN != null)) {
  			String tSplitStr[] = tDN.substring(tDN.indexOf("CN=")).split("@");
  			if (tSplitStr != null && tSplitStr.length > 2
  					&& tSplitStr[2] != null)
  				tPart = tSplitStr[2];
  		}
  		return tPart;
  	}
docs: 获取证书的CN
  @param aCert
  @return