Document root element "struts-config", must match DOCTYPE root "null"

写了一个是struts的程序, 启动tomcat的时候会遇到如下 error :

SEVERE: Parse Error at line 2 column 15: Document is invalid: no grammar found.

org.xml.sax.SAXParseException: Document is invalid: no grammar found.

SEVERE: Parse Error at line 2 column 15: Document root element "struts-config", must match DOCTYPE root "null".

org.xml.sax.SAXParseException: Document root element "struts-config", must match DOCTYPE root "null".

上述error的出现是因为在编写 配置文件 struts-config.xml 的时候,在xml中没有添加如下声明造成的:

<!DOCTYPE struts-config PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 1.3//EN"

"http://struts.apache.org/dtds/struts-config_1_3.dtd">