今天要写struts2.1.8中的validation的练习，于是乎凭着以前看过的记忆，边查文档边写……但是随后遇到的问题，令我很恼火，上网一查，原来遇到的人也不少……
问题描述：按照struts2.1.8的文档，我贴一下应有的代码
struts.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.enable.DynamicMethodInvocation" value="false" />
<constant name="struts.devMode" value="true" />
<package name="default" namespace="/reg" extends="struts-default">
<default-action-ref name="quizAction" />
<action name="quizAction" class="com.linrui.action.QuizAction">
<result name="success">/Success.jsp</result>
<result name="input">/Input.jsp</result>
</action>
<action name="index">
<result>/index.jsp</result>
</action>
</package>
<!-- Add packages here -->
</struts>
QuizAction.java
package com.linrui.action;
import com.opensymphony.xwork2.ActionSupport;
public class QuizAction extends ActionSupport {
private String name;
private int age;
private String answer;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAnswer() {
return answer;
}
public void setAnswer(String answer) {
this.answer = answer;
}
@Override
public String execute() throws Exception {
return SUCCESS;
}
}
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<% String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort() + path + "/";
%>
<%@ taglib uri="/struts-tags" prefix="s"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>Validation - Basic</title>
<s:head />
</head>
<body>
<s:form method="post" action="quizAction" validate="true" namespace="/reg">
<s:textfield label="Name" name="name"/>
<s:textfield label="Age" name="age"/>
<s:textfield label="Favorite color" name="answer"/>
<s:submit/>
</s:form>
</body>
</html>
QuizAction-validation.xml (该文件和Action的类文件放在同一目录下，这里采用ActionName-validation.xml的命名方式) <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator 1.0.2//EN" "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd"> <validators> <field name="name"> <field-validator type="requiredstring"> <message>You must enter a name</message> </field-validator> </field> <field name="age"> <field-validator type="int"> <param name="min">1</param> <param name="max">100</param> <message>Only people ages 4 to 8 may take this quiz</message> </field-validator> </field> </validators>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
按照上面的代码（官方文档也是这么写的），导入相应的包，然后发布之后，就可以用了。。。一开始我也是这么想的，但是发布以后开始报错！
报错信息如下：
后台报错数据如下：
严重:
Method public java.util.List org.apache.struts2.components.Form.getValidators(java.lang.String) threw an exception when invoked on org.apache.struts2.components.Form@1c01ba9
The problematic instruction:
----------
==> list tag.getValidators("${tagName}") as validator [on line 46, column 9 in template/xhtml/form-close-validate.ftl]
in include "/${parameters.templateDir}/xhtml/form-close-validate.ftl" [on line 25, column 1 in template/xhtml/form-close.ftl]
----------
Java backtrace for programmers:
----------
freemarker.template.TemplateModelException: Method public java.util.List org.apache.struts2.components.Form.getValidators(java.lang.String) threw an exception when invoked on org.apache.struts2.components.Form@1c01ba9
at freemarker.ext.beans.SimpleMethodModel.exec(SimpleMethodModel.java:130)
at freemarker.core.MethodCall._getAsTemplateModel(MethodCall.java:93)
..................
然后我便检查了我的代码，把能修改的地方都修改了……但是还是没有效果，其中包括把index.jsp里头的<s:form action=“xxxx” 把XXX后头加上.action （其实不加也行），或者是把namespace去掉并加到action里头（那样的话，就不是客户端验证了，而是服务器验证），一样都是没有用……
其实最根本的原因是我访问的时候，采用直接访问jsp的方式（也就是处理流是从 .jsp -> action -> .jsp）来进行，所以才报出那样的错误信息。最后我将index.jsp配置到struts.xml中，采用访问action的方式（action -> action or .jsp ->.jsp），就正常处理了……
总结：struts2在使用验证框架的时候，要让struts2来作为整个web application的URL访问总控制器（也就是所有的地址访问都要先经过拦截器），不然就会出现上述的错误……不过它的这种特性，使得程序的安全机制更高！
Allen
2011-02-19
