Trouble with serializing HashMaps

Hi Scott,
I've got following trouble I am using Apache SOAP as RPC
now I tried to give my serverroutine Maps in Vectors
I am getting a Nullpointexception, because I am using HashMaps which allow
null-values
in the Map serializier a HashTable is used which does not allow null-values.
What is the reason a HashTable is performing for Maps an not a HashMap?
If a Map is used, which does not allow null-values the client will allready
know that while filling it with entries. So I believe it does not need to be
so restrictive.
Since passing a Map is really a standard I don't prefer writing a new
serializer/deserializer on my own.

My Exception is the following:

java.lang.NullPointerException 	at
java.util.Hashtable.put(Hashtable.java:393) 	at
java.util.Hashtable.putAll(Hashtable.java:467) 	at
org.apache.soap.encoding.soapenc.MapSerializer.marshall(Unknown Source) 	at
org.apache.soap.util.xml.XMLJavaMappingRegistry.marshall(Unknown Source) 	at
org.apache.soap.encoding.soapenc.VectorSerializer.marshall(Unknown Source)
at org.apache.soap.encoding.soapenc.ParameterSerializer.marshall(Unknown
Source) 	at org.apache.soap.rpc.RPCMessage.serializeParams(Unknown Source)
at org.apache.soap.rpc.RPCMessage.marshall(Unknown Source) 	at
org.apache.soap.Body.marshall(Unknown Source) 	at
org.apache.soap.Envelope.marshall(Unknown Source) 	at
org.apache.soap.transport.http.SOAPHTTPConnection.send(Unknown Source) 	at
org.apache.soap.rpc.Call.invoke(Unknown Source) 	at
org.apache.soap.rpc.Call.invoke(Unknown Source) 	at
de.mc.etnbestterm.data.SoapCallingDataHolder.callSoaply(SoapCallingDataHolde
r.java:93) 	at
de.mc.etnbestterm.data.OrderDataHolder.orderArtikelsInBasket(OrderDataHolder
.java:2047) 	at
de.mc.etnbestterm.gui.WKBestellungsPanel.sendAnforderung(WKBestellungsPanel.
java:324) 	at
de.mc.etnbestterm.gui.WKBestellungsPanel.m_artikelSpecialButton_actionPerfor
med(WKBestellungsPanel.java:225) 	at
de.mc.etnbestterm.gui.BasketPanel$4.actionPerformed(BasketPanel.java:104)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786)
at
javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButto
n.java:1839) 	at
javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:4
20) 	at
javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258) 	at
javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener
.java:245) 	at java.awt.Component.processMouseEvent(Component.java:5100) 	at
java.awt.Component.processEvent(Component.java:4897) 	at
java.awt.Container.processEvent(Container.java:1569) 	at
java.awt.Component.dispatchEventImpl(Component.java:3615) 	at
java.awt.Container.dispatchEventImpl(Container.java:1627) 	at
java.awt.Component.dispatchEvent(Component.java:3477) 	at
java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483) 	at
java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198) 	at
java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128) 	at
java.awt.Container.dispatchEventImpl(Container.java:1613) 	at
java.awt.Window.dispatchEventImpl(Window.java:1606) 	at
java.awt.Component.dispatchEvent(Component.java:3477) 	at
java.awt.EventQueue.dispatchEvent(EventQueue.java:456) 	at
java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.ja
va:201) 	at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java
:151) 	at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145) 	at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137) 	at
java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

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