1---:java.lang.NoClassDefFoundError: org/apache/struts2/dojo/views/jsp/ui/HeadTag
解决办法：原因缺少了dojo的JAR包，引入即可:struts2-dojo-plugin-2.1.2.jar
The "head" tag renders required JavaScript code to configure Dojo and is required in order to use any of the tags included in the Dojo plugin.
--------------------
If you are planning to nest tags from the Dojo plugin, make sure you set parseContent="false", otherwise each request made by the inner tags will be performed twice.
2---:Unable to load configuration. -bean -jar:file:/F:/Struts2/Struts2/WebRoot/WEB-INF/lib/struts2-core- 2.1.2.jar!/struts-default.xml:46:178
Caused by: Unable to load bean: type:org.apache.struts2.dispatcher.multipart.MultiPartRequest class:org.apache.struts2.dispatcher.multipart.JakartaMultiPartRequest -bean -jar:file:/F:/Struts2/Struts2/WebRoot/WEB-INF/lib/struts2-core-2.1.2.jar!/struts-default.xml:46:178
Caused by: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/RequestContext
解决办法：缺少JAR包，引入commons-fileupload-1.2.1.jar，commons-io-1.3.2.jar即可
3---:No tag "datetimepicker" defined in tag library imported with prefix "s"
原因版本问题：缺少struts-dojo-plugin JAR包，以及HTML的,<HEAD></HEAD>中没有使用<s:head/>标签
If you're using Struts 2.1.x you're probablymissing the>struts-dojo-plugin. Michal's reference below applies to Struts 2.1.xonly. In the lasts versions (since 2.0.9 I guess), all AJAX are in dojo> plugin.
> > So you need toinclude <%@ taglib uri="/struts-dojo-tags" prefix="sx"%>
> > and <sx:head/>
> >( Temp1:
<sx:datetimepicker name="picker" />
Temp2:
<sx:datetimepicker type="time" name="picker" /><br/>
Temp3:
<sx:datetimepicker value="%{'2008-06-08'}" name="picker" />
Temp4:
<sx:datetimepicker value="date" name="picker" />)
> > and call :<sx:datetimepicker .../>
4---:使用TILES框架
If you use the Tiles 2 plugin, check your tiles.xml file(s) to ensure they contain a DOCTYPE.
<!DOCTYPE tiles-definitions PUBLIC "-//Apache Software Foundation//DTD Tiles Configuration 2.0//EN" "http://tiles.apache.org/dtds/tiles-config_2_0.dtd"><tiles-definitions>
5---:struts2中不支持EL表达式
Struts2.1 tags do not allow evaluation of JSP EL within their attributes.Instead, Struts2 tags evaluate attribute values as OGNL. Allowing bothexpression languages within the same attribute opens major securityvulnerabilities.
6---文件上传过程中取不到文件名和文件类型，即都取到NULL
原因：如果页面中file的name=“a”则我们ACTION中设置String aContentType,String aFileName;(此两个其实无所谓，关键是SET方法)
setA(File file)(){}; setAContentType(String s){};setAFileName(String name){} 即格式如下：setXContentType() setXFileName().X代表你给FILE取的NAME名字
必须和它相同，固定格式
7---严重: Unable to parse request
org.apache.commons.fileupload.FileUploadBase$SizeLimitExceededException: the request was rejected because its size (8523356) exceeds the configured maximum (2097152)
at org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.<init>(FileUploadBase.java:914)2008-5-27 17:46:51 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [struts.valueStack]
2008-5-27 17:46:51 com.opensymphony.xwork2.util.logging.commons.CommonsLogger error
严重: the request was rejected because its size (8523356) exceeds the configured maximum (2097152)
2008-5-27 17:46:51 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [org.apache.catalina.jsp_file]
原因：上传文件大小超过预定大小，可以在struts.properties配置文件中设置struts.multipart.maxSize=XXX（XXX为文件大小）
8---配置了文件类型限制后，当传错误类型可以拦截不让用户上传该文件，可是跳转的页面却没有跳转到input配置的错误页面，而是返回
到了success正确页面。
严重: Content-Type not allowed: filedata "upload__5b01657_11a329d4dcf__8000_00000000.tmp" text/plain
《我的打印输出DEBUG语句内容:File:null FlieName:null type:null》即拦截类型成功了
java.lang.NullPointerException
at java.io.FileInputStream.<init>(FileInputStream.java:103)
at com.study.web.util.FileUploadUtil.uploadFile(FileUploadUtil.java:36)
at com.study.web.action.UploadFileAction.execute(UploadFileAction.java:58)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)。。。
2008-5-29 10:59:07 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [org.apache.catalina.jsp_file]
2008-5-29 10:59:07 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [struts]
2008-5-29 10:59:07 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Removing file filedata \tmp\upload__5b01657_11a329d4dcf__8000_00000000.tmp
原因及解决办法：在该文件上传Action中只配置了FileUploadInterceptor后缺少配置了defaultStack拦截器.
在ACTION中配置玩defaultStack拦截器后改错误消失。
9---struts.properties中全局配置文件大小，再使用默认FileUploadInterceptor拦截器时候能实现拦截的功能但是后台出现异常。
严重: Unable to parse request
org.apache.commons.fileupload.FileUploadBase$SizeLimitExceededException: the request was rejected because its size (380) exceeds the configured maximum (10)
at org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.<init>(FileUploadBase.java:914)
原因：未知。将全局配置中的限制大小去掉，再重新在ACTION中覆盖配置FileUploadInterceptor拦截器设置大小和文件类型限制，可消除异常。
10---多文件上传中，其中一个传被限制的文件如限制aplication/msword(即.doc)文件，允许传文本文件。然而当夹杂在一起传的时候，后台能截获类型错误不可传信息，但是
实际却还是上传成功。
严重: Content-Type not allowed: filedata "upload_4d958287_11a33e76ab9__8000_00000007.tmp" application/msword
file is :\tmp\upload_4d958287_11a33e76ab9__8000_00000006.tmp fileName:project.txt fileType:text/plain
file is :\tmp\upload_4d958287_11a33e76ab9__8000_00000007.tmp fileName:application base.doc fileType:application/msword
file is :\tmp\upload_4d958287_11a33e76ab9__8000_00000008.tmp fileName:zhongqi-bug.txt fileType:text/plain
原因：忘记了继承ActionSupport类。继承后异常消失。
11--文件上传异常，不能创建File文件
Cannot create type class java.io.File from value C:\Documents and Settings\admin\桌面\OrderReporterServiceImp.java - [unknown location]
原因：忘记了在form表单里将enctype设置成文件上传格式：enctype="multipart/form-data"
12--当使用限制文件类型和大小的时候抛出空指针异常
java.lang.NullPointerExceptiondemo.struts2.action.ValidatFileUploadAction.execute(ValidatFileUploadAction.java:71)sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)原因：在ACTION中配置了fileUpload拦截器后忘记了配置默认拦截器：defautlStack。注意当ACTION中配置自己的拦截器后需要显示配置默认
拦截器defaultStack
13--在国际化时候抛空指针异常：
16:31:12,812 ERROR [jsp]:253 - Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException at java.text.MessageFormat.applyPattern(MessageFormat.java:414)
at java.text.MessageFormat.<init>(MessageFormat.java:350)
at com.opensymphony.xwork2.DefaultTextProvider.getText(DefaultTextProvider.java:70)
原因：忘记了在struts.xml中配置国际化常量，或者在struts.properties中配置全局国际化常量 struts.custom.i18n.resources=globeMessage
14-- struts action的配置文件加载失败：
Unable to load configuration. - result - file:/D:/Java/apache-tomcat-5.5.20/webapps/mysts/WEB-INF/classes/test.xml:10:26
Caused by: No result type specified for result named 'error', perhaps the parent package does not specify the result type? - result - file:/D:/Java/apache-tomcat-5.5.20/webapps/mysts/WEB-INF/classes/test.xml:10:26
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.buildResults(XmlConfigurationProvider.java:609)
原因：忘记了继承包struts-default
15-- struts action 配置文件注意事项：
1. 别忘记了继承struts-default默认配置包
2.如果配置命名空间，一定要以"/"开始，例如：namespace="/test"
3.每个模块struts action配置文件中都可以配置全局result，global-result 经测试不会冲突，STRTUS会智能寻找该Action请求的
模块STRUTS ACTION配置包
关键字: 警告: no configuration found for the specified action
警告: No configuration found for the specified action: 'ShowMessage' in namespace: ''. Form action defaulting to 'action' attribute's literal value.
解决方法：
经过测试发现，是没有正确使用tag的原因，这种情况下，正确的写法应该是，<s:form name="login" method="post" action="login" >
您是否添加了action这个呢？