read value from property file in spring mvc

Question

I create a springmvc web application. I want to read property file. I have a properties file app.properties located in resources

p.id=1
p.name=test

I have a class Constant.java

public class Constant{

    public static PropertyFile{
        public static final String APP="resources/app";
    }
    public static PropertyKey{
        public static final String P_ID = "p.id";
        public static final String P_Name = "p.name";
    }

}

I have an AppSetting.java

public class AppSetting{
       private static final ResourceBundle resource =
            ResourceBundle.getBundle(Constants.PropertyFile.APP);
       public String getId(){
        return resource.getString(Constant.PropertyKey.P_ID);
        }

}

when I called it AppSetting.getId(); it cannot find resource. Can you help me?