Intergrating with Spring

I used Struts 2.0.1 and intergated with spring.
The problem was when I requested a jsp page that contained <s:form> tag, all action was instantiated without calling. Note that the scope of Action Beans in spring config file were prototype. It means that the beans instantiaed once without calling but just at the first request to that page.
when I switched to Stuts 2.0.5, this problem occured:
<pre>
SEVERE: Exception starting filter struts
Cannot locate the chosen ObjectFactory implementation: spring - [unknown location]
at org.apache.struts2.config.BeanSelectionProvider.alias(BeanSelectionProvider.java:224)
at org.apache.struts2.config.BeanSelectionProvider.alias(BeanSelectionProvider.java:195)
at org.apache.struts2.config.BeanSelectionProvider.register(BeanSelectionProvider.java:155)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:130)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:398)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:455)
at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:225)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:308)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:79)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3563)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4133)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:910)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:873)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:474)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1118)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:310)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:680)
at org.apache.catalina.startup.Catalina.start(Catalina.java:536)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:275)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
</pre>