About the querymessage method of MQAdmin.java

[xhrg]

 /**
     * Query messages
     *
     * @param topic message topic
     * @param key message key index word
     * @param maxNum max message number
     * @param begin from when
     * @param end to when
     * @return Instance of QueryResult
     */
    QueryResult queryMessage(final String topic, final String key, final int maxNum, final long begin,
        final long end) throws MQClientException, InterruptedException;

When I test, the key cannot be "" or null， If the key can be empty, it will be much more convenient to query the message according to the time

我测试的时候，发现参数key不能为空或者null 如果key可以为空，根据时间查询消息会方便很多。