NPE當調用託管屬性的獲取者

Question

我正在學習Spring與Hibernate，並創建一個使用JSF作爲前端框架的電影租賃應用程序。

我在我的註冊bean中有一個應用程序範圍的託管屬性，它是視圖範圍。在用於將用戶詳細信息插入數據庫的register()方法中，我調用服務定位器實現bean以獲取對所需服務實現的引用。但是，當我調用服務定位器屬性的getter時，我得到了一個N​​PE。

以下是我的管理豆...

註冊豆

@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; 
    } 
} 

基地豆

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

    protected IServiceLocator getServiceLocator() { 
     return serviceLocator; 
    } 

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

服務定位豆

@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; 
    } 
} 

這裏是因爲看到我的Eclipse控制檯堆棧跟蹤

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 

我使用

• JSF 2.1（鑽嘴魚科）
• 的Hibernate 4.1
• 春季3.2
• Tomcat 7
• Eclipse 3.7

有人請指出，如果我錯過了什麼？

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> 

Answer 1

這篇文章幫我做的代碼工作：http://www.javacodegeeks.com/2012/04/jsf-2-primefaces-3-spring-3-hibernate-4.html

但是，代碼不工作，如果我把註冊bean作爲view scoped。任何人都可以請幫我找出相同的原因嗎？

更新：找到了ViewScope問題的解決方案：http://blog.harezmi.com.tr/spring-view-scope-for-jsf-2-users/