@Injection不适用于CDI bean

Question

我有一个CDI bean,我正在使用@ConversationScoped.当我尝试为Conversation对象执行@Inject时,我得到一个NPE.

  @ConversationScoped
@Named("customerbean")
public class CustomerBean implements Serializable {

    @Inject
    private Conversation conversation;    

    private static final EntityManagerFactory emf = Persistence.createEntityManagerFactory("ba");
    private EntityManager em;
    private Customer customer;
    boolean disabled;    

    public CustomerBean() {
        beginConversation();
        customer = new Customer();
        em = emf.createEntityManager();
        disabled = false;
    }

    private void beginConversation() {
        if (this.conversation.isTransient()) {
            this.conversation.begin();
            return;
        }
        throw new IllegalStateException();
    }

我在WEB-INF目录中有beans.xml文件(尽管是空的).例外情况如下:

INFO: Exception when handling error trying to reset the response.
com.google.common.collect.ComputationException: java.lang.RuntimeException: java
.lang.NullPointerException
        at com.google.common.collect.ComputingConcurrentHashMap$ComputingMapAdap
ter.get(ComputingConcurrentHashMap.java:397)
        at org.jboss.weld.bean.proxy.ClientProxyProvider.getClientProxy(ClientPr
oxyProvider.java:102)
        at org.jboss.weld.el.AbstractWeldELResolver.lookup(AbstractWeldELResolve
r.java:115)
        at org.jboss.weld.el.AbstractWeldELResolver.getValue(AbstractWeldELResol
ver.java:96)
        at org.jboss.weld.environment.servlet.util.ForwardingELResolver.getValue
(ForwardingELResolver.java:49)
        at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:67)
        at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELR
esolver.java:176)

Answer 1

您new不能使用任何类型的初始化逻辑来创建CDI bean ,也不能使用构造函数.

这背后的原因是CDI bean(如EJB,Spring bean,JSF bean)具有独立的生命周期,并由相关容器管理.你不能依赖于"传统"理解何时(以及多久)new被调用.使用producer来创​​建新bean,并@PostConstruct用于在创建之后执行的任何逻辑.

这应该为您提供CDI的良好开端.随意发表更多问题:)