Cannot call sendError() after the response has been committed

解决方法:因为如果你的bean类有的字段为空的话，就会出现下面的问题，所以转换成json 的时候，把空的数据去掉

 //除去不要的字段
     JsonConfig config=new JsonConfig();
     config.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT);
     config.setExcludes(new String[]{
     "account",
     
     
     });

FreeMarker template error!

Method public java.lang.String org.apache.commons.lang.exception.NestableRuntimeException.getMessage(int) threw an exception when invoked on net.sf.json.JSONException: java.lang.reflect.InvocationTargetException
The problematic instruction:
----------
==> ${msg[0]} [on line 68, column 29 in org/apache/struts2/dispatcher/error.ftl]
----------

Java backtrace for programmers:
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freemarker.template.TemplateModelException: Method public java.lang.String org.apache.commons.lang.exception.NestableRuntimeException.getMessage(int) threw an exception when invoked on net.sf.json.JSONException: java.lang.reflect.InvocationTargetException
	at freemarker.ext.beans.SimpleMethodModel.exec(SimpleMethodModel.java:130)
	at freemarker.ext.beans.SimpleMethodModel.get(SimpleMethodModel.java:138)
	at freemarker.core.DynamicKeyName.dealWithNumericalKey(DynamicKeyName.java:111)
	at freemarker.core.DynamicKeyName._getAsTemplateModel(DynamicKeyName.java:90)
	at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
	at freemarker.core.Expression.getStringValue(Expression.java:93)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:76)
	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.IfBlock.accept(IfBlock.java:82)
	at freemarker.core.Environment.visit(Environment.java:210)
	at freemarker.core.IteratorBlock$Context.runLoop(IteratorBlock.java:179)
	at freemarker.core.Environment.visit(Environment.java:417)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:102)
	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.IfBlock.accept(IfBlock.java:82)
	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 org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:749)
	at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:506)
	at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
	at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1008)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1852)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
	at freemarker.ext.beans.SimpleMemberModel.unwrapArguments(SimpleMemberModel.java:85)
	at freemarker.ext.beans.SimpleMethodModel.exec(SimpleMethodModel.java:106)
	... 43 more