JFinal中配置类实例无法创建的问题 创建报错

运行一个maven项目是报错，说WebConfig配置类无法实例化？如下所示 java.lang.RuntimeException: Can not create instance of class: net.dreamlu.common.WebConfig. Please check the config in web.xml.

配置文件WebConfig.java：

public class WebConfig extends JFinalConfig {
@Override
public void configConstant(Constants me) {
// 加载配置文件
loadPropertyFile("config.txt");
isdev = getPropertyToBoolean("isdev", false);
me.setDevMode(false);

.......(正常配置）

web.xml配置：

<display-name>JFinal2.0-beetl-training</display-name>
<filter>
<filter-name>jfinal</filter-name>
<filter-class>com.jfinal.core.JFinalFilter</filter-class>
<async-supported>true</async-supported>
<init-param>
<param-name>configClass</param-name>
<param-value>net.dreamlu.common.WebConfig</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>jfinal</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>