struts.xml文件中没有提示代码，导入去约束dtd文件。
在myeclipse中 Preferences 下的 XML Catalog 中 add （事先将dtd文件放置到工程目录中） 选择 workspace 选择dtd文件；然后选择 System Id ，将key为空间名称（"http://struts.apache.org/dtds/struts-2.0.dtd"） 即可。
struts-2.1.7.dtd文件
<?xml version="1.0" encoding="UTF-8"?>
<!--
/*
* $Id: struts-2.0.dtd 651946 2008-04-27 13:41:38Z apetrelli $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
-->
<!-- START SNIPPET: strutsDtd -->
<!--
Struts configuration DTD.
Use the following DOCTYPE
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.1.7//EN"
"http://struts.apache.org/dtds/struts-2.1.7.dtd">
-->
<!ELEMENT struts ((package|include|bean|constant)*, unknown-handler-stack?)>
<!ATTLIST struts
order CDATA #IMPLIED
>
<!ELEMENT package (result-types?, interceptors?, default-interceptor-ref?, default-action-ref?, default-class-ref?, global-results?, global-exception-mappings?, action*)>
<!ATTLIST package
name CDATA #REQUIRED
extends CDATA #IMPLIED
namespace CDATA #IMPLIED
abstract CDATA #IMPLIED
externalReferenceResolver NMTOKEN #IMPLIED
>
<!ELEMENT result-types (result-type+)>
<!ELEMENT result-type (param*)>
<!ATTLIST result-type
name CDATA #REQUIRED
class CDATA #REQUIRED
default (true|false) "false"
>
<!ELEMENT interceptors (interceptor|interceptor-stack)+>
<!ELEMENT interceptor (param*)>
<!ATTLIST interceptor
name CDATA #REQUIRED
class CDATA #REQUIRED
>
<!ELEMENT interceptor-stack (interceptor-ref*)>
<!ATTLIST interceptor-stack
name CDATA #REQUIRED
>
<!ELEMENT interceptor-ref (param*)>
<!ATTLIST interceptor-ref
name CDATA #REQUIRED
>
<!ELEMENT default-interceptor-ref (#PCDATA)>
<!ATTLIST default-interceptor-ref
name CDATA #REQUIRED
>
<!ELEMENT default-action-ref (#PCDATA)>
<!ATTLIST default-action-ref
name CDATA #REQUIRED
>
<!ELEMENT default-class-ref (#PCDATA)>
<!ATTLIST default-class-ref
class CDATA #REQUIRED
>
<!ELEMENT global-results (result+)>
<!ELEMENT global-exception-mappings (exception-mapping+)>
<!ELEMENT action (param|result|interceptor-ref|exception-mapping)*>
<!ATTLIST action
name CDATA #REQUIRED
class CDATA #IMPLIED
method CDATA #IMPLIED
converter CDATA #IMPLIED
>
<!ELEMENT param (#PCDATA)>
<!ATTLIST param
name CDATA #REQUIRED
>
<!ELEMENT result (#PCDATA|param)*>
<!ATTLIST result
name CDATA #IMPLIED
type CDATA #IMPLIED
>
<!ELEMENT exception-mapping (#PCDATA|param)*>
<!ATTLIST exception-mapping
name CDATA #IMPLIED
exception CDATA #REQUIRED
result CDATA #REQUIRED
>
<!ELEMENT include (#PCDATA)>
<!ATTLIST include
file CDATA #REQUIRED
>
<!ELEMENT bean (#PCDATA)>
<!ATTLIST bean
type CDATA #IMPLIED
name CDATA #IMPLIED
class CDATA #REQUIRED
scope CDATA #IMPLIED
static CDATA #IMPLIED
optional CDATA #IMPLIED
>
<!ELEMENT constant (#PCDATA)>
<!ATTLIST constant
name CDATA #REQUIRED
value CDATA #REQUIRED
>
<!ELEMENT unknown-handler-stack (unknown-handler-ref*)>
<!ELEMENT unknown-handler-ref (#PCDATA)>
<!ATTLIST unknown-handler-ref
name CDATA #REQUIRED
>
<!-- END SNIPPET: strutsDtd -->