jcaptcha是专业的解决方案，做到了极致，没必要自己去写了
下载之：http://sourceforge.net/projects/jcaptcha/files/
根据他官方的例子，在struts中集成方法如下
环境：struts 1.3.x jcaptcha 1.0
1. 加载lib
把jcaptcha-1.0-all.jar 和 jcaptcha-integration-struts-1.0.jar 放到工程的lib里面，并设置包含之
2. 配置struts-config.xml
加plug-in描述
<plug-in className=“com.octo.captcha.module.struts.CaptchaServicePlugin”/>
加引用的 action
<action-mappings>这个里面加以下代码
<!– add the render action–>
<action
path=“/jcaptcha”
type=“com.octo.captcha.module.struts.image.RenderImageCaptchaAction”
>
</action>
即：可用 http://server/proj/jcaptcha.do 调用(如果你设置的是 *.do) http://server/proj/do/jcapcha(如果你设置的是 /do/*的话) 显示生成的图片
运行起来后，在浏览器中应该可以看到图片了
3. jsp中集成
如 login.jsp中
最前面加入taglib定义
<%– Add the jcaptcha taglib–%>
<%@ taglib uri=“http://jcaptcha.sourceforge.net” prefix=“jcaptcha”%>
增加显示和校验代码
<%– Add the jcaptcha form part–%>
<input type=“text” name=“jcaptcha_response” />
<!– 加入错误提示，改成用errors了–>
<font class=“required_error_font”> <html:errors property=“jcaptcha_error_msg” /></font><br/>
<font size=“-1″ color=“#6f6f6f”><jcaptcha:question/></font><br/>
<%– Add the image–%>
<img name=“jcaptcha” id=“jcaptcha” onclick=“refresh_jcaptcha(this)” src=“<%=request.getContextPath()%>/do/jcaptcha” alt=“click to refresh” style=“cursor:pointer;”/>
增加了个点击刷新的功能，脚本如下
<script language=“Javascript”>
function refresh_jcaptcha(obj){
//alert(obj);
obj.src=”<%=request.getContextPath()%>/do/jcaptcha?” + Math.random();
}
</script>
4. 在提交页面对应的Action.excute()中增加校验代码处理 request
我把他封装成了函数
public boolean isJcaptchaOK(HttpServletRequest request)
{
log.debug(“enter captcha challenge verification”);
CaptchaService service = CaptchaServicePlugin.getInstance()
.getService();
String responseKey = CaptchaServicePlugin.getInstance()
.getResponseKey();
String captchaID = CaptchaModuleConfigHelper.getId(request);
String challengeResponse = request.getParameter(responseKey);
if (log.isDebugEnabled())
log.debug(“response for id “ + captchaID + ” : “ + challengeResponse);
request.removeAttribute(responseKey);
boolean isResponseCorrect = false;
if (challengeResponse != null)
try {
isResponseCorrect = service.validateResponseForID(captchaID,
challengeResponse).booleanValue();
} catch (CaptchaServiceException e) {
log.debug(“Error during challenge verification”, e);
request.setAttribute(CaptchaServicePlugin
.getInstance().getMessageKey(),
CaptchaModuleConfigHelper
.getMessage(request));
log.debug(“forward to error with message : “ + CaptchaModuleConfigHelper.getMessage(request));
throw(e);//抛出程序应用异常
}
if (isResponseCorrect) {
log.debug(“correct : forward to success”);
return true;//正确
}
if (log.isDebugEnabled()) {
log.debug(“false : forward to failure with message : “
+ CaptchaModuleConfigHelper.getMessage(request));
log.debug(“in request attribute key : “
+ CaptchaServicePlugin.getInstance().getMessageKey());
}
ActionErrors errors = new ActionErrors();//用ActionError替换了他自己的Message
errors.add(“jcaptcha_error_msg”, new ActionMessage(
“error.jcaptcha.error.inputInvalid”));
this.addErrors(request, errors);
return false;
}
—–
excute(…)中：
if(!isJcaptchaOK(request))
return mapping.findForward(“return_form”); //返回页面
return mapping.findForward(“global_success”);
——
大功告成
