問題的起因是修改了Axis2自動生成的代碼，以便在后臺打印出請求和響應的格式

public com.sean.AddResponse add(com.sean.Add add0)throws java.rmi.RemoteException {org.apache.axis2.context.MessageContext _messageContext = null;org.apache.axiom.soap.SOAPEnvelope env = null;org.apache.axiom.soap.SOAPEnvelope _returnEnv = null;try {......env = toEnvelope(getFactory(_operationClient.getOptions().getSoapVersionURI()), add0,optimizeContent(new javax.xml.namespace.QName("http://sean.com", "add")),new javax.xml.namespace.QName("http://sean.com", "add"));......_returnEnv = _returnMessageContext.getEnvelope();java.lang.Object object = fromOM(_returnEnv.getBody().getFirstElement(), com.sean.AddResponse.class,getEnvelopeNamespaces(_returnEnv));return (com.sean.AddResponse) object;} catch (org.apache.axis2.AxisFault f) {......} finally {System.out.println("request:+\n" + env.toString());System.out.println("response:\n" + _returnEnv.toString());if (_messageContext.getTransportOut() != null) {_messageContext.getTransportOut().getSender().cleanup(_messageContext);}} }

雖然后臺能夠打印出請求，但是在打印響應時卻會拋出異常：org.apache.axiom.om.NodeUnavailableException

主要還是代碼修改的有問題，AXIS2的版本為1.6.2，在其lib包中的AXIOM版本為1.2.13，在我的工程中將其換為1.2.14

在AXIOM1.2.14的API中（參見：https://ws.apache.org/axiom/apidocs/org/apache/axiom/om/NodeUnavailableException.html）提到：

Exception indicating that a requested node cannot be returned because it is no longer available. A node may become unavailable because it has been consumed by a method such asOMSerializable.serializeAndConsume(XMLStreamWriter) orOMContainer.getXMLStreamReaderWithoutCaching(), or because one of its ancestors has been discarded usingOMNode.discard().

在獲得_returnEnv對象后，調用了fromOM方法獲得結果對象，fromOM方法如下：

private java.lang.Object fromOM(org.apache.axiom.om.OMElement param,java.lang.Class type, java.util.Map extraNamespaces)throws org.apache.axis2.AxisFault {try {if (com.sean.Add.class.equals(type)) {return com.sean.Add.Factory.parse(param.getXMLStreamReaderWithoutCaching());}if (com.sean.AddResponse.class.equals(type)) {return com.sean.AddResponse.Factory.parse(param.getXMLStreamReaderWithoutCaching());}} catch (java.lang.Exception e) {throw org.apache.axis2.AxisFault.makeFault(e);}return null; }

_returnEnv的類型是org.apache.axiom.soap.SOAPEnvelope，而org.apache.axiom.soap.SOAPEnvelope是org.apache.axiom.om.OMContainer的子類

所以在finally塊中調用_returnEnv.toString()時，由于_returnEnv中保存的節點因為被OMContainer.getXMLStreamReaderWithoutCaching()方法消費而變得不可用，所以將拋出NodeUnavailableException異常

解決方式如下：

public com.sean.AddResponse add(com.sean.Add add0)throws java.rmi.RemoteException {org.apache.axis2.context.MessageContext _messageContext = null;org.apache.axiom.soap.SOAPEnvelope env = null;org.apache.axiom.soap.SOAPEnvelope _returnEnv = null;String request = "";String response = "";try {......env = toEnvelope(getFactory(_operationClient.getOptions().getSoapVersionURI()), add0,optimizeContent(new javax.xml.namespace.QName("http://sean.com", "add")),new javax.xml.namespace.QName("http://sean.com", "add"));request = env.toString();......_returnEnv = _returnMessageContext.getEnvelope();response = _returnEnv.toString();java.lang.Object object = fromOM(_returnEnv.getBody().getFirstElement(), com.sean.AddResponse.class,getEnvelopeNamespaces(_returnEnv));return (com.sean.AddResponse) object;} catch (org.apache.axis2.AxisFault f) {......} finally {System.out.println("request:+\n" + request);System.out.println("response:\n" + response);if (_messageContext.getTransportOut() != null) {_messageContext.getTransportOut().getSender().cleanup(_messageContext);}} }

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