有没有接触过Java开源shuzheng/zheng的？有一些疑问：报错

https://gitee.com/shuzheng/zheng

这是地址

它有一个filter

public class UpmsAuthenticationFilter extends AuthenticationFilter {

    private static final Logger LOGGER = LoggerFactory.getLogger(UpmsAuthenticationFilter.class);

    // 局部会话key
    private final static String ZHENG_UPMS_CLIENT_SESSION_ID = "zheng-upms-client-session-id";
    // 单点同一个code所有局部会话key
    private final static String ZHENG_UPMS_CLIENT_SESSION_IDS = "zheng-upms-client-session-ids";

    @Autowired
    UpmsSessionDao upmsSessionDao;

    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        Subject subject = getSubject(request, response);
        Session session = subject.getSession();
        // 判断请求类型
        String upmsType = PropertiesFileUtil.getInstance("zheng-upms-client").get("zheng.upms.type");
        session.setAttribute(UpmsConstant.UPMS_TYPE, upmsType);
        if ("client".equals(upmsType)) {
            return validateClient(request, response);
        }

        if ("server".equals(upmsType)) {
            return subject.isAuthenticated();
        } 
        return false;
    }
}

这里有一句

 String upmsType = PropertiesFileUtil.getInstance("zheng-upms-client").get("zheng.upms.type");

这里看起来是通过PropertiesFileUtil去获取当前请求是客户端还是服务器端，然而...我没太明白它是怎么实现判断的？求解！！！！！

/**
 * 资源文件读取工具
 * @author shuzheng
 * @date 2016年10月15日
 */
public class PropertiesFileUtil {

    // 当打开多个资源文件时，缓存资源文件
    private static HashMap<String, PropertiesFileUtil> configMap = new HashMap<String, PropertiesFileUtil>();
    // 打开文件时间，判断超时使用
    private Date loadTime = null;
    // 资源文件
    private ResourceBundle resourceBundle = null;
    // 默认资源文件名称
    private static final String NAME = "config";
    // 缓存时间
    private static final Integer TIME_OUT = 60 * 1000;

    // 私有构造方法，创建单例
    private PropertiesFileUtil(String name) {
        this.loadTime = new Date();
        this.resourceBundle = ResourceBundle.getBundle(name);
    }

    public static synchronized PropertiesFileUtil getInstance() {
        return getInstance(NAME);
    }

    public static synchronized PropertiesFileUtil getInstance(String name) {
        PropertiesFileUtil conf = configMap.get(name);
        if (null == conf) {
            conf = new PropertiesFileUtil(name);
            configMap.put(name, conf);
        }
        // 判断是否打开的资源文件是否超时1分钟
        if ((System.currentTimeMillis() - conf.getLoadTime().getTime()) > TIME_OUT) {
            conf = new PropertiesFileUtil(name);
            configMap.put(name, conf);
        }
        return conf;
    }

    // 根据key读取value
    public String get(String key) {
        try {
            String value = resourceBundle.getString(key);
            return value;
        } catch (MissingResourceException e) {
            return "";
        }
    }

    // 根据key读取value(整形)
    public Integer getInt(String key) {
        try {
            String value = resourceBundle.getString(key);
            return Integer.parseInt(value);
        } catch (MissingResourceException e) {
            return null;
        }
    }

    // 根据key读取value(布尔)
    public boolean getBool(String key) {
        try {
            String value = resourceBundle.getString(key);
            if ("true".equals(value)) {
                return true;
            }
            return false;
        } catch (MissingResourceException e) {
            return false;
        }
    }

    public Date getLoadTime() {
        return loadTime;
    }

}

这是那个工具类

我想不明白的是，为什么能根据读取配置文件来判断当前前来的是server还是client？？？？？？？

求助！！！！