严重: Servlet.service() for servlet [default] in context with path [/whiteStruts2] threw exception
java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:462)
at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:770)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:505)
at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
......等以下我就不复制粘贴了
网页有如下异常：FreeMarker template error!
Expression title is undefined on line 4, column 18 in test.ftl.
The problematic instruction:
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==> ${title} [on line 4, column 16 in test.ftl]
----------
Java backtrace for programmers:
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freemarker.core.InvalidReferenceException: Expression title is undefined on line 4, column 18 in test.ftl.
at freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:124)
at freemarker.core.Expression.getStringValue(Expression.java:118)
at freemarker.core.Expression.getStringValue(Expression.java:93)
at freemarker.core.DollarVariable.accept(DollarVariable.java:76)
at freemarker.core.Environment.visit(Environment.java:208)
at freemarker.core.MixedContent.accept(MixedContent.java:92)
at freemarker.core.Environment.visit(Environment.java:208)
at freemarker.core.Environment.process(Environment.java:188)
at freemarker.template.Template.process(Template.java:237)
at org.apache.struts2.views.freemarker.FreemarkerResult.doExecute(FreemarkerResult.java:187)
at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)
at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:361)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:265)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)解决方法：在freemarker的应用中，出现如上错误是因为，你的ftl模板中的某一个（比如：${name}）,其中name并没有放入Map中或者不存在这样的key.
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原文：http://10973493.blog.51cto.com/10963493/1888267