Tomcat中web.xml语句顺序问题

报错信息

The content of element type "web-app" must match "(icon?,display-name?,description?,distributable?,context-param*,filter*,filter-mapping*,listener*,servlet*,servlet-mapping*,session-config?,mime-mapping*,welcome-file-list?,error-page*,taglib*,resource-env-ref*,resource-ref*,security-constraint*,login-config?,security-role*,env-entry*,ejb-ref*,ejb-local-ref*)". 

 原因和DTD 的格式要求有关，原文摘录如下：

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So for the 2.3 version of the DTD, you have to put the tags in the correct order. You have:

<web-app>  <servlet></servlet>  <servlet-mapping></servlet-mapping>  <servlet></servlet>  <servlet-mapping></servlet-mapping>  <servlet></servlet>  <servlet-mapping></servlet-mapping>  <!-- ... -->  <listener></listener></web-app>

But the DTD says it must be:

<web-app>  <listener></listener>  <servlet></servlet>  <servlet></servlet>  <servlet></servlet>  <!-- ... -->  <servlet-mapping></servlet-mapping>  <servlet-mapping></servlet-mapping>  <servlet-mapping></servlet-mapping>  <!-- ... --></web-app>

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

The error message tells you the order they must be in:

 content of element type "web-app" must match "(icon?,display-name?,description?,distributable?,context-param*,filter*,filter-mapping*,listener*,servlet*,servlet-mapping*,session-config?,mime-mapping*,welcome-file-list?,error-page*,taglib*,resource-env-ref*,resource-ref*,security-constraint*,login-config?,security-role*,env-entry*,ejb-ref*,ejb-local-ref*)"

Means the order is:

icon (0 or 1 times)display-name (0 or 1 times)description (0 or 1 times)distributable (0 or 1 times)context-param (0 or more times)filter (0 or more times)filter-mapping (0 or more times)listener (0 or more times)servlet (0 or more times)servlet-mapping (0 or more times)session-config (0 or 1 times)mime-mapping (0 or more times)welcome-file-list (0 or 1 times)error-page (0 or more times)taglib (0 or more times)resource-env-ref (0 or more times)resource-ref (0 or more times)security-constraint (0 or more times)login-config (0 or 1 times)security-role (0 or more times)env-entry (0 or more times)ejb-ref (0 or more times)ejb-local-ref (0 or more times)

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

i also want to know that
are tags supposed to be in some order in version 2.4, or i can have them in any order ?


Answer:   

The 2.4 spec can be in any order.