java.lang.NullPointerException: attempted to save null
   at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:580)
   at net.sf.hibernate.id.ForeignGenerator.generate(ForeignGenerator.java:37)
   at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:599)
   at com.twofi.auction.implementations.HomeInsuranceControlBeanImpl.createNewAuctionItem(Unknown Source)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:324)
   at org.springframework.aop.framework.InvokerInterceptor.invoke(InvokerInterceptor.java:54)
   at org.springframework.aop.framework.MethodInvocationImpl.proceed(MethodInvocationImpl.java:216)
   at org.springframework.aop.framework.AopProxy.invoke(AopProxy.java:102)
   at $Proxy1.createNewAuctionItem(Unknown Source)
   at com.twofi.auction.actions.CreateHomeInsuranceAction.doExecute(Unknown Source)
   at webwork.action.ActionSupport.execute(ActionSupport.java:151)
   at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:131)
   at webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:174)

public class HomeInsurance {
   private int auctionid;
   private AuctionItem auctionitem;

public class AuctionItem {
   private int auctionid;

<hibernate-mapping>
   <class name="com.twofi.auction.objects.AuctionItem" table="auctionitem">
      <id name="auctionid" type="long" column="auctionid" unsaved-value="any">
         <generator class="increment" />
      </id>
      <property name="userid" type="int" column="userid" />
      <property name="createdate" type="timestamp" column="createdate" />
      <property name="starttime" type="timestamp" column="starttime" />
      <property name="endtime" type="timestamp" column="endtime" />
      <property name="lengthtime" type="int" column="lengthtime" />
      <property name="startprice" type="double" column="startprice" />
      <property name="reservateprice" type="double" column="reservateprice" />
      <property name="incrementprice" type="double" column="incrementprice" />
      <property name="winneruserid" type="int" column="winneruserid" />
      <property name="status" type="string" column="status" />
      <property name="autopostpone" type="true_false" column="autopostpone" />
      <property name="repost" type="short" column="repost" />
      <property name="repostcount" type="short" column="repostcount" />
   </class>
</hibernate-mapping>

<hibernate-mapping>
    <class name="com.twofi.auction.objects.HomeInsurance" table="homeinsurance">
      <id name="auctionid" type="long" column="auctionid" unsaved-value="any">
         <generator class="foreign">
            <param name="property">auctionitem</param>
         </generator>
      </id>
      <one-to-one name="auctionitem" class="com.twofi.auction.objects.AuctionItem" cascade="all" constrained="true" />
        <property name="proposername" type="string" column="proposername"/>
        <property name="idcardno" type="string" column="idcardno"/>
        <property name="contactno" type="string" column="contactno"/>
        <property name="contactaddress" type="string" column="contactaddress"/>
        <property name="insureaddress" type="string" column="insureaddress"/>
        <property name="area" type="double" column="area"/>
      <property name="ageofbuilding" type="int" column="ageofbuilding" />
        <property name="endinsurance" type="date" column="endinsurance"/>
        <property name="startinsurance" type="date" column="startinsurance"/>
   </class>
</hibernate-mapping>

auctionitem
============
auctionid
userid
createdate
starttime
lengthtime
startprice
reservateprice
incrementprice
winneruserid
status
autopostpone
repost
repostcount

homeinsurance
==============
auctionid
proposername
idcardno
contactno
contactaddress
insureaddress
area
ageofbuilding
startinsurance
endinsurance