Spring 调用托管属性的getter时的NPE

我正在用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。在将用户详细信息插入数据库的

register（）

方法中，我调用服务定位器实现bean以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，我会得到一个NPE

以下是我的托管bean

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;
   }
}

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

   protected IServiceLocator getServiceLocator() {
      return serviceLocator;
   }

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

@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;
   }
}

基豆

@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;
   }
}

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

   protected IServiceLocator getServiceLocator() {
      return serviceLocator;
   }

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

@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;
   }
}

服务定位器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;
   }
}

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

   protected IServiceLocator getServiceLocator() {
      return serviceLocator;
   }

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

@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;
   }
}

这是在我的Eclipse控制台中看到的stacktrace

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

我正在使用

• JSF2.1（莫哈拉）
• 冬眠4.1
• 春季3.2
• 雄猫7
• Eclipse 3.7

如果我遗漏了什么，有人能指出吗

更新：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：

但是，如果我将注册Bean保持为

查看范围

，则代码不起作用。有人能帮我找出同样的原因吗

---

更新：找到了ViewScope问题的解决方案：

@BalusC-正如我所说，我正在学习Spring+Hibernate，因此我的设计将是临时的。但不，我的服务定位器不是Springbean。它封装的用户服务属性是Springbean。我已经添加了我的spring配置文件。我确实读过一篇文章，其中使用了JSF2.0和SpringMVC，但有点混乱，所以现在我只使用依赖注入和SpringORM为hibernate部分提供的hibernate模板。这里的最后一个链接已断开。您可能希望修复该链接或添加实际适用于您的解决方案。否则，这个答案根本不值得一读。指定链接时，请在问题和/或答案中至少引用一些要点，以便在链接断开的情况下对将来的访问者有用。@Vrushank:我可以知道为什么

get（）

方法是同步的吗？我看不到这一点。它是强制性的吗？此外，

registerDestructionCallback（）

、

getConversationId（）

和

getViewMap（）

方法的主体在此处留空。这些方法有什么意义吗？当这些方法需要按照您上一篇？P.S.中所示进行编码时，这对我来说很好（Primefaces 3.5，Spring 3.2.2）。谢谢。@Lion:除非您希望高并发性，否则同步

get（）

方法不是强制性的。其他方法是实现契约的一部分，因此需要被重写，特别是销毁回调，以便正确地对bean生命周期进行映像。@Vrushank:好的。。。嗯，但这是蒂尼问的：）：）。你应该通知他。谢谢