Initialization of bean "handlingMapping" error!!!

I started my Tomcat and got the following error,

Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'handlerMapping' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Initialization of bean failed; nested exception is java.lang.NullPointerException: null
java.lang.NullPointerException

The codes in my xfire-servlet,

<import resource="classpath:org/codehaus/xfire/spring/xfire.xml" />
<bean id="jaxbTypeMappingRegistry"
class="org.codehaus.xfire.jaxb2.JaxbTypeRegistry"
init-method="createDefaultMappings" />
<bean id="webAnnotations"
class="org.codehaus.xfire.annotations.jsr181.Jsr181WebAnnotations" />
<bean id="handlerMapping"
class="org.codehaus.xfire.spring.remoting.Jsr181HandlerMapping">
<property name="typeMappingRegistry">
<ref bean="jaxbTypeMappingRegistry" />
</property>
<property name="xfire">
<ref bean="xfire" />
</property>
<property name="webAnnotations">
<ref bean="webAnnotations" />
</property>
</bean>

Could anyone explain what's the cause, and how to correct it? Thanks!!!