web.xml中添加taglib标签后

原文地址：http://hi.baidu.com/tediou/blog/item/5d0dce556f7a4a828d5430ca.html

现象为如下的web.xml在Eclipse Helios中出现警告信息

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>WebTest</display-name>
<welcome-file-list>
   <welcome-file>index.html</welcome-file>
   <welcome-file>index.htm</welcome-file>
   <welcome-file>index.jsp</welcome-file>
   <welcome-file>default.html</welcome-file>
   <welcome-file>default.htm</welcome-file>
   <welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
   <servlet-name>action</servlet-name>
   <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
   <init-param>
    <param-name>config</param-name>
    <param-value>/WEB-INF/struts-config.xml</param-value>
   </init-param>
   <init-param>
    <param-name>debug</param-name>
    <param-value>3</param-value>
   </init-param>
   <init-param>
    <param-name>detail</param-name>
    <param-value>3</param-value>
   </init-param>
   <load-on-startup>0</load-on-startup>
</servlet>
<servlet-mapping>
   <servlet-name>action</servlet-name>
   <url-pattern>*.do</url-pattern>
</servlet-mapping>
<filter>
   <filter-name>Set Character Encoding</filter-name>
   <filter-class>WebTest.SetCharacterEncodingFilter</filter-class>
</filter>
<filter-mapping>
   <filter-name>Set Character Encoding</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>
<taglib>
   <taglib-uri>/tags/struts-bean</taglib-uri>
   <taglib-location>/WEB-INF/lib/struts-bean.tld</taglib-location>
</taglib>
<taglib>
   <taglib-uri>/tags/struts-html</taglib-uri>
   <taglib-location>/WEB-INF/lib/struts-html.tld</taglib-location>
</taglib>
<taglib>
   <taglib-uri>/tags/struts-logic</taglib-uri>
   <taglib-location>/WEB-INF/lib/struts-logic.tld</taglib-location>
</taglib>
</web-app>
错误信息：
Description Resource Path Location Type
cvc-complex-type.2.4.a: Invalid content was found starting with element 'taglib'.
One of '{
"http://java.sun.com/xml/ns/j2ee":description,
"http://java.sun.com/xml/ns/j2ee":display-name,
"http://java.sun.com/xml/ns/j2ee":icon,
"http://java.sun.com/xml/ns/j2ee":distributable,
"http://java.sun.com/xml/ns/j2ee":context-param,
"http://java.sun.com/xml/ns/j2ee":filter,
"http://java.sun.com/xml/ns/j2ee":filter-mapping,
"http://java.sun.com/xml/ns/j2ee":listener,
"http://java.sun.com/xml/ns/j2ee":servlet,
"http://java.sun.com/xml/ns/j2ee":servlet-mapping,
"http://java.sun.com/xml/ns/j2ee":session-config,
"http://java.sun.com/xml/ns/j2ee":mime-mapping,
"http://java.sun.com/xml/ns/j2ee":welcome-file-list,
"http://java.sun.com/xml/ns/j2ee":error-page,
"http://java.sun.com/xml/ns/j2ee":jsp-config,
"http://java.sun.com/xml/ns/j2ee":security-constraint,
"http://java.sun.com/xml/ns/j2ee":login-config,
"http://java.sun.com/xml/ns/j2ee":security-role,
"http://java.sun.com/xml/ns/j2ee":env-entry,
"http://java.sun.com/xml/ns/j2ee":ejb-ref,
"http://java.sun.com/xml/ns/j2ee":ejb-local-ref,
"http://java.sun.com/xml/ns/j2ee":service-ref,
"http://java.sun.com/xml/ns/j2ee":resource-ref,
"http://java.sun.com/xml/ns/j2ee":resource-env-ref,
"http://java.sun.com/xml/ns/j2ee":message-destination-ref,
"http://java.sun.com/xml/ns/j2ee":message-destination,
"http://java.sun.com/xml/ns/j2ee":locale-encoding-mapping-list}' is expected.
web.xml /WebTest/WebContent/WEB-INF line 41 XML Problem

原因：
在jsp2.0中,且2.4版的DTD验证中,taglib描述符,正确写法是放到<jsp-config></jsp-config>描述符中。

解决办法：
1）将<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
改为<web-app>，去除验证。

2）按规范，把taglib标签放进jsp-config标签中。如下：
<jsp-config>
   <taglib>
    <taglib-uri>/tags/struts-bean</taglib-uri>
    <taglib-location>/WEB-INF/lib/struts-bean.tld</taglib-location>
   </taglib>
   <taglib>
    <taglib-uri>/tags/struts-html</taglib-uri>
    <taglib-location>/WEB-INF/lib/struts-html.tld</taglib-location>
   </taglib>
   <taglib>
    <taglib-uri>/tags/struts-logic</taglib-uri>
    <taglib-location>/WEB-INF/lib/struts-logic.tld</taglib-location>
   </taglib>
</jsp-config>