我在内容模型中添加了一个名为aaa地自定义字段，在内容中调用是，如果该字段的内容为空就会报错，请问如何判断自定义的字段是否为空呢？谢了

[#if content.attr.aaa??]
aaa
[#else]
bbb
[/#if]
这样判断也不行，还是会报错。
The required "id" paramter is missing. The problematic instruction: ---------- ==> user-directive cms_content 

因该你那样判断是没错的？还有什么错误信息吗？

完整的信息如下：

The required "id" paramter is missing.
The problematic instruction:
----------
==> user-directive cms_content [on line 70, column 41 in WEB-INF/t/cms/www/test/content/test-新闻.html]
----------

Java backtrace for programmers:
----------
com.jeecms.common.web.freemarker.ParamsRequiredException: The required "id" paramter is missing.
at com.jeecms.cms.action.directive.ContentDirective.getId(ContentDirective.java:74)
at com.jeecms.cms.action.directive.ContentDirective.execute(ContentDirective.java:48)
at freemarker.core.Environment.visit(Environment.java:263)
at freemarker.core.UnifiedCall.accept(UnifiedCall.java:126)
at freemarker.core.Environment.visit(Environment.java:210)
at freemarker.core.MixedContent.accept(MixedContent.java:92)
at freemarker.core.Environment.visit(Environment.java:210)
at freemarker.core.Environment.process(Environment.java:190)
at freemarker.template.Template.process(Template.java:237)
at com.jeecms.common.web.springmvc.SimpleFreeMarkerView.renderMergedTemplateModel(SimpleFreeMarkerView.java:114)
at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:167)
at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1047)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:817)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.jeecms.common.web.ProcessTimeFilter.doFilter(ProcessTimeFilter.java:38)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:555)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:774)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:703)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:896)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
at java.lang.Thread.run(Thread.java:636)

操作系统版本： Linux 2.6.35-22-generic-pae
操作系统类型： i386 32位
用户、目录、临时目录： tomcat6, /var/lib/tomcat6, /tmp/tomcat6-tmp
JAVA运行环境： OpenJDK Runtime Environment 1.6.0_20-b20
JAVA虚拟机： OpenJDK Server VM 17.0-b16

id没有取到，一开始你那里会报错吗？就是需要判断为空就不报错了？

只要是自定义字段没有内容就会报错，我以为先进行判断就不会出问题了，结果还是出错...

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