请教一个空指针异常问题 谢谢 了

Question

HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception javax.servlet.ServletException
org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:545)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:486)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
filter.Filter1.doFilter(Filter1.java:28)
root cause java.lang.NullPointerException
com.yourcompany.struts.action.CarAddAction.execute(CarAddAction.java:54)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
filter.Filter1.doFilter(Filter1.java:28)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.30 logs.

Answer 1

java.lang.NullPointerException 
s  = cs.save(car); 

Answer 2

<bean name="carAdd" 
class="com.yourcompany.struts.action.CarAddAction" abstract="false" 
singleton="false" lazy-init="default" autowire="default" 
dependency-check="default"> 
<property name="cs"> 
<ref bean="carService" /> 
</property> 
</bean> <bean id="carService" class="com.abc.service.CarService" 
abstract="false" singleton="true" lazy-init="default" 
autowire="default" dependency-check="default"> 
<property name="cd"> 
<ref bean="carDAO" /> 
</property> 
</bean> <ref bean="carService" />
<ref bean="carDAO" /> 
两个你没注入吧?

Answer 3

<bean name="carAdd"      ----->"/carAdd"
class="com.yourcompany.struts.action.CarAddAction" abstract="false" 
singleton="false" lazy-init="default" autowire="default" 
dependency-check="default"> 
<property name="cs"> 
<ref bean="carService" /> 
</property> 
</bean>