使用Spring Webflow时的会话对象

Question

我有几个变量需要存储在会话中，因为它们应该可用，直到页面关闭。

我提出了可以存储值的会话对象，这样我就可以在必要时通过注入将它们引用到任何类。

@Component
@Scope("session")
public class SessionObjects {
    /**
     * Boradcaster id of the atmosphere
     */
    private String broadCasterId;
    /**
     * Atmosphere Resource Id of specific session
     */
    private String senderId;
    public String getBroadCasterId() {
        return broadCasterId;
    }
    public void setBroadCasterId(String broadCasterId) {
        this.broadCasterId = broadCasterId;
    }
    public String getSenderId() {
        return senderId;
    }
    public void setSenderId(String senderId) {
        this.senderId = senderId;
    }
}

但是当我启动应用程序服务器时，它会因此错误而失败。

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'wb': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.emyed.whiteboard.controller.SessionObjects com.emyed.whiteboard.defaults.wb.baseMB; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:288) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1116) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:626) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932) ~[spring-context-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479) ~[spring-context-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:389) ~[spring-web-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:294) ~[spring-web-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112) [spring-web-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939) [catalina.jar:7.0.42]
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434) [catalina.jar:7.0.42]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [catalina.jar:7.0.42]
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901) [catalina.jar:7.0.42]
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877) [catalina.jar:7.0.42]
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:633) [catalina.jar:7.0.42]
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:976) [catalina.jar:7.0.42]
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1653) [catalina.jar:7.0.42]
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) [na:1.6.0_25]
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) [na:1.6.0_25]
    at java.util.concurrent.FutureTask.run(FutureTask.java:138) [na:1.6.0_25]
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [na:1.6.0_25]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [na:1.6.0_25]
    at java.lang.Thread.run(Thread.java:662) [na:1.6.0_25]
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.emyed.whiteboard.controller.SessionObjects com.emyed.whiteboard.defaults.wb.baseMB; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:514) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    ... 27 common frames omitted
Caused by: java.lang.NullPointerException: null
    at org.springframework.web.context.request.SessionScope.get(SessionScope.java:91) ~[spring-web-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:329) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) ~[spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]

示例wb类

@Named
public class Wb implements Serializable{

    @Autowired
    private SessionObjects sessionObj;

    /**
     * Creates a new whiteboard
     *
     * @return string outcome for navigation
     */
    public WhiteboardIdentifiers create() {
        String senderId = UUID.randomUUID().toString();
        String whiteboardID = UUID.randomUUID().toString();
        UserData creator = new UserData(senderId, getCreator(),null);
        return createWhiteboard.create( senderId,  whiteboardID,  creator);
    }


    public DisplayWhiteboard setDisplayWhiteboard(WhiteboardIdentifiers wbIdentifiers){
       ........
            // set the id's in the baseMB
            sessionObj.setBroadCasterId(whiteboardId);
            //Chat Controller
        ......
            sessionObj.setSenderId(senderId);
            whiteboard.getUserController().activateUser(senderId);

    }
}