Hey JiaPei,
I think your code is right. Well, in my
struts based applications, the *.properties files are located in the \WEB-INF\classes\resources directory.
Example of configuring the file \WEB-INF\classes\resources\application.properties in struts-config.xml:
...
<message-resources parameter="resources.application"/>
...
I hope it helps!
Best regards,