SSH2增加<tx:method />后报空指针？

前段时间给SSH增加了个事务的配置：
<bean id="txManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory"/>
</bean>
<aop:config>
<aop:pointcut expression="execution(* com.yb..*.*(..))" id="transactionPointcut"/>
<aop:advisor advice-ref="txAdvice" pointcut-ref="transactionPointcut"/>
</aop:config>
<tx:advice id="txAdvice" transaction-manager="txManager">
<tx:attributes>
<tx:method name="get*" read-only="true" propagation="NOT_SUPPORTED"/>
<tx:method name="*" />
</tx:attributes>
</tx:advice>以上就是在执行get方法的时候不执行事务，然后获取数据的时候出现了一个问题，不知道是不是方法的原因呢还是配置的原因（错误见末尾）？
第239行代码是这样的（wfid确认是不为空的）：
Workfireflow wf=(Workfireflow)this.definition.objectDAO.get(Workfireflow.class, Integer.parseInt(wfid));实现的方法如下：
package com.yb.daoImpl;import java.io.Serializable;
import java.util.List;import org.hibernate.Hibernate;
import org.hibernate.Query;
import org.hibernate.Session;
import org.springframework.orm.hibernate3.HibernateCallback;
import org.springframework.orm.hibernate3.HibernateTemplate;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;import com.yb.bean.Page;
import com.yb.dao.ObjectDAO;
import com.yb.file.fileop;public class DAOImpl extends HibernateDaoSupport implements ObjectDAO {
public Object get(Class clazz, Serializable id) {
try{
 return this.getHibernateTemplate().get(clazz, id);
   }catch(Exception e)
  {
 fileop.debug(String.valueOf(new StringBuffer("DAOImpl中get(Class clazz, Serializable id)异常").append(e.toString())));
 return null;
  }
 }
}
报的错误：
Struts Problem Report
Struts has detected an unhandled exception: Messages:  
File: com/yb/struts/action/GWDefinitionAction.java 
Line number: 239 
--------------------------------------------------------------------------------
Stacktraces
java.lang.NullPointerException 
    com.yb.struts.action.GWDefinitionAction.definitiontemple(GWDefinitionAction.java:239)
    com.yb.struts.action.GWDefinitionAction$$FastClassByCGLIB$$5b10593e.invoke()
    net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
    org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:700)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
    org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
    org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:635)
    com.yb.struts.action.GWDefinitionAction$$EnhancerByCGLIB$$707fc738.definitiontemple()
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:441)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243)
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252)
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
    org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
    org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)
    org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    java.lang.Thread.run(Thread.java:619)
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