Struts 2 TextField 标签有属性但没有值

Question

我有一个以下格式的 html 标签：

<input type="text" name="username" id="username" placeholder="Enter your username" required>

我正在尝试将其转换为由 struts 标签呈现（以便在验证错误时，页面重新加载用户输入的值）：

<s:textfield name="username" id="username" placeholder="Enter your username" required />

不幸的是，struts 抛出以下异常：

org.apache.jasper.JasperException: /index.jsp(58,110) PWC6212: equal symbol expected
    at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:49)
    at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:344)
    at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:101)
    at org.apache.jasper.compiler.Parser.parseAttribute(Parser.java:220)
    at org.apache.jasper.compiler.Parser.parseAttributes(Parser.java:170)
    at org.apache.jasper.compiler.Parser.parseCustomTag(Parser.java:1394)
    at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1636)
    at org.apache.jasper.compiler.Parser.parse(Parser.java:152)
    at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:210)
    at org.apache.jasper.compiler.ParserController.parse(ParserController.java:111)
    at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:157)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:370)
    at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:595)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:344)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:457)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:351)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:917)
    at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:398)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:88)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:217)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:369)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:100)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:78)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)

我猜测 Struts 不喜欢“必需”没有值。如何编辑 Struts 标签以附加不带值的“必需”文本？我们有一个现有的 javascript 库，它依赖于“required”的存在，而不是“required=”“”或其他东西。

Answer 1

对于任何发现此问题并运行 Struts 2.3.12 或更高版本的人来说，这里有一个答案 - 网络上似乎很少有关于此更改的文档...

在 2.3.12 版本之前，struts2 有一个可以添加到输入字段的必需属性。此属性纯粹是为了将字段标记为必填字段，并且可用于通过使用 .ftl 文件在字段旁边添加必需的星号/星号（例如） - 它不运行任何验证。在您的代码中可能看起来像这样：

<s:textfield key="name" type="text" required="true"/>

但是在版本 2.3.12 之后，required 属性被 requiredLabel 属性替换。它的工作方式完全相同，可能如下所示：

<s:textfield key="name" type="text" requiredLabel="true"/>

这个变化是因为html5引入了required属性。但请注意，如果您当前想在 struts2 中使用它，则当前无法在不提供值的情况下使用它（正如 html5 规范所说可以）——这似乎会破坏 struts。例如，这是行不通的：

<s:textfield key="name" type="text" required />

相反，您需要编写：

<s:textfield key="name" type="text" required="required" />