我们使用
- JSF 2.1
- RichFaces 4
- OmniFaces 1.5
我们得到以下异常：
java.io.NotSerializableException: org.omnifaces.taghandler.ImportConstants$ConstantsMap
当使用<o:importConstants>和javax.faces.STATE_SAVING_METHOD作为客户端时。
以前有人见过这个吗？解决办法是什么？
感谢您为解决此问题提供的任何帮助。
修复很简单，只需让org.omnifaces.util.MapWrapper也实现Serializable即可。我已经提交了它，并在今天的最新1.8快照中提供。然而，原因很奇怪。我没想到它会被保存到JSF状态，因为它是一个EL表达式。所以我看得更远一点，只是为了学习。
为了完整起见，以下是我在Tomcat 7.0.47上使用Mojarra 2.1.28时遇到的stacktrace，它具有客户端状态保存和<f:event>，其中常量作为方法参数传递，如下所示：
<o:importConstants type="com.example.Constants" />
<f:event type="preRenderView" listener="#{bean.method(Constants.SOME)}" />
仅打开页面时已发生异常，不需要回发。
java.io.NotSerializableException: org.omnifaces.taghandler.ImportConstants$ConstantsMap
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1181)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at org.apache.el.ValueExpressionLiteral.writeExternal(ValueExpressionLiteral.java:109)
at java.io.ObjectOutputStream.writeExternalData(ObjectOutputStream.java:1456)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1427)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at java.util.HashMap.writeObject(HashMap.java:1100)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at org.apache.el.lang.VariableMapperImpl.writeExternal(VariableMapperImpl.java:59)
at java.io.ObjectOutputStream.writeExternalData(ObjectOutputStream.java:1456)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1427)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at org.apache.el.MethodExpressionImpl.writeExternal(MethodExpressionImpl.java:308)
at java.io.ObjectOutputStream.writeExternalData(ObjectOutputStream.java:1456)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1427)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at com.sun.faces.facelets.el.TagMethodExpression.writeExternal(TagMethodExpression.java:152)
at java.io.ObjectOutputStream.writeExternalData(ObjectOutputStream.java:1456)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1427)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1541)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1506)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1541)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1506)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1541)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1506)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at java.util.ArrayList.writeObject(ArrayList.java:710)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at java.util.HashMap.writeObject(HashMap.java:1100)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at com.sun.faces.renderkit.ClientSideStateHelper.doWriteState(ClientSideStateHelper.java:424)
at com.sun.faces.renderkit.ClientSideStateHelper.writeState(ClientSideStateHelper.java:210)
at com.sun.faces.renderkit.ResponseStateManagerImpl.writeState(ResponseStateManagerImpl.java:122)
at com.sun.faces.application.StateManagerImpl.writeState(StateManagerImpl.java:113)
at com.sun.faces.application.view.WriteBehindStateWriter.flushToWriter(WriteBehindStateWriter.java:225)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:464)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:125)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:286)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
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:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
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:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)
和riiight。。ValueExpressionLiteral出现在画面中。枚举值被解析为EL文字。ValueExpressionLiteral将序列化文字值（计算值本身）以进行状态保存，而不是具体表达式#{Constants.SOME}。这毕竟是有道理的，枚举无论如何都是常量。