好吧，我找到了答案：

RedisTemplate template = (RedisTemplate) applicationContext.getBean("redisTemplate");
        JedisConnectionFactory redisConnectionFactory = (JedisConnectionFactory) template.getConnectionFactory();
        //关闭连接池
        redisConnectionFactory.destroy();
        redisConnectionFactory.setShardInfo(null);
        redisConnectionFactory.setHostName(host);
        redisConnectionFactory.setPort(port);
        redisConnectionFactory.setPassword(password);
        redisConnectionFactory.setDatabase(database);
        //重新创建连接池
        redisConnectionFactory.afterPropertiesSet();
        template.setConnectionFactory(redisConnectionFactory);