调用托管属性的 getter 时出现 NPE

我正在使用 Hibernate 学习 Spring，并使用 JSF 作为前端框架创建一个电影租赁应用程序。

我的注册 bean 中有一个应用程序范围的托管属性，它是视图范围的。在里面register()方法将用户详细信息插入数据库中，我调用服务定位器实现 bean 来获取对所需服务实现的引用。但是，当我调用服务定位器属性的 getter 时，我得到一个 NPE。

以下是我的管理豆...

注册Bean

@ManagedBean
@ViewScoped
public class RegistrationBean extends BaseBean implements Serializable
{
   private static final long serialVersionUID = -6449858513581500971L;

   private String userID;
   private String password;
   private String firstName;
   private String lastName;
   private String email;
   private String addressLine1;
   private String addressLine2;
   private String city;
   private String state;
   private String pincode;

   public RegistrationBean() {
      super();
   }

   // getter / setters...

   public String register() 
   {
      String nextPage = null;
      try {
         RegistrationDetails userDetails = ModelBuilder.populateRegistrationData(this);

         // NPE at this line. getServiceLocator() returns null
         int registrationID = getServiceLocator().getUserService().registerUser(userDetails);

         nextPage = "success";
      }
      catch (RegistrationException e) {
         LOGGER.error(e.getMessage());
      }
      return nextPage;
   }
}

基豆

public class BaseBean
{
   @ManagedProperty("#{serviceLocator}")
   protected IServiceLocator serviceLocator;

   protected IServiceLocator getServiceLocator() {
      return serviceLocator;
   }

   public void setServiceLocator(IServiceLocator serviceLocator) {
      this.serviceLocator = serviceLocator;
   }
}

服务定位器 Bean

@ManagedBean
@ApplicationScoped
public class ServiceLocator implements IServiceLocator
{
   private static final String USER_SERVICE = "userService";

   public ServiceLocator() {
      super();
      final ServletContext sc = FacesUtils.getServletContext();
      this.webAppContext = WebApplicationContextUtils.getRequiredWebApplicationContext(sc);
      this.userService = (IUserService) webAppContext.getBean(USER_SERVICE);
   }

   private ApplicationContext webAppContext;

   private IUserService userService;

   @Override
   public IUserService getUserService() {
      return userService;
   }

   public ApplicationContext getWebAppContext() {
      return webAppContext;
   }
}

这是我的 Eclipse 控制台中看到的堆栈跟踪

Oct 14, 2012 10:28:39 PM com.sun.faces.lifecycle.InvokeApplicationPhase execute
WARNING: #{registrationBean.register}: java.lang.NullPointerException
javax.faces.FacesException: #{registrationBean.register}: java.lang.NullPointerException
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    ... 23 more
Caused by: java.lang.NullPointerException
    at com.clixflix.managedbeans.RegistrationBean.register(RegistrationBean.java:118)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
    ... 24 more

我在用

• JSF 2.1（莫哈拉）
• 休眠4.1
• 春季3.2
• 雄猫7
• 日食3.7

如果我错过了什么，有人可以指出吗？

UPDATE：Spring配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans 
       http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

   <bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
      <property name="configLocation" value="/WEB-INF/hibernate.cfg.xml" />
   </bean>

   <bean id="hibernateTemplate" class="org.springframework.orm.hibernate3.HibernateTemplate">
      <property name="sessionFactory" ref="sessionFactory" />
   </bean>

   <bean id="userDAO" class="com.clixflix.dao.impl.UserDAOImpl">
      <constructor-arg index="0" ref="hibernateTemplate" />
   </bean>

   <bean id="userService" class="com.clixflix.services.impl.UserService">
      <constructor-arg index="0" ref="userDAO" />
   </bean>

</beans>

这篇文章帮助我使代码正常工作：http://www.javacodegeeks.com/2012/04/jsf-2-primefaces-3-spring-3-hibernate-4.html

但是，如果我将注册 Bean 保留为view scoped。谁能帮我找出同样的原因吗？

更新：找到 ViewScope 问题的解决方案：http://blog.harezmi.com.tr/spring-view-scope-for-jsf-2-users/