调用托管属性的 getter 时的 NPE [英] NPE when invoking getter of managed property
问题描述
我正在使用 Hibernate 学习 Spring，并且正在创建一个使用 JSF 作为前端框架的电影租赁应用程序.
I am learning Spring with Hibernate and am creating a movie rental application using JSF as front end framework.
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，我得到了一个 NPE.
I have an application scoped managed property in my registration bean which is view scoped. In the register() method to insert the user details in the database, I invoke the service locator implementation bean to get a reference to the required service implementation. However, I get an NPE when I invoke the getter of the service locator property.
以下是我管理的 bean...
Following are my managed beans...
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;
}
}
基础豆
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;
}
}
这是在我的 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
我正在使用
- JSF 2.1 (Mojarra)
- 休眠 4.1
- 春季 3.2
- 雄猫 7
- Eclipse 3.7
有人可以指出我是否遗漏了什么吗?
Could someone please point out if I have missed something??
更新:Spring 配置文件
UPDATE: Spring config file
<?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>
推荐答案
这篇文章帮助我使代码工作:http://www.javacodegeeks.com/2012/04/jsf-2-primefaces-3-spring-3-hibernate-4.html
This post helped me to make the code work : http://www.javacodegeeks.com/2012/04/jsf-2-primefaces-3-spring-3-hibernate-4.html
但是，如果我将注册 Bean 保持为 view scoped，代码将不起作用.任何人都可以帮我找出相同的原因吗?
However, the code does not work if I keep the Registration Bean as view scoped. Can anyone please help me figure out the reason for the same?
更新:找到了 ViewScope 问题的解决方案:http://blog.harezmi.com.tr/spring-view-scope-for-jsf-2-users/
UPDATE: Found the solution for the ViewScope issue : http://blog.harezmi.com.tr/spring-view-scope-for-jsf-2-users/
这篇关于调用托管属性的 getter 时的 NPE的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
