ejbFacade为空 [英] ejbFacade is null

问题描述

我从jsf页面调用了managedBean OverzichtAlle.java overzichtAlleGroepen.xhtml

I call the managedBean OverzichtAlle.java from the jsf page overzichtAlleGroepen.xhtml

但是当我得到这个页面时，我得到了错误的事件，不能实例化managedBeans.OverzichtAlle由于Nullpointerexception ...

But when I get on this page i get the errormessage can't instantiate managedBeans.OverzichtAlle due to a Nullpointerexception...

当我调试时，我看到我的ejbFacade是空的..

When I debug, I see that my ejbFacade is null..

这是EJB

@EJB private ProjecttypeEFacade ejbFacade;

这是我的构造函数：

public OverzichtAlle() 
{
    projE = ejbFacade.findAll();
    omvormenProjectTypes();
}

projE是一个列表（实体列表）

projE is a List (entity-list)

我做错了什么？

推荐答案

@EJB bean的构造之后，c $ c>被注入。这是EJB注入管理器，即在构造之前不可能调用bean setter方法：

@EJBs are injected after bean's construction. It's for the EJB injection manager namely not possible to call a bean setter method before constructing it:

overzichtAlle.setEjbFacade(ejbFacade);
OverzichtAlle overzichtAlle = new OverzichtAlle();

而是在幕后发生以下情况：

Instead, the following is happening behind the scenes:

OverzichtAlle overzichtAlle = new OverzichtAlle();
overzichtAlle.setEjbFacade(ejbFacade);

所以 ejbFacade 是 可以在bean的构造函数中使用。正常的做法是使用 @PostConstruct 方法。

So the ejbFacade is not available inside bean's constructor. The normal approach is to use a @PostConstruct method for this.

@PostConstruct
public void init() {
    projE = ejbFacade.findAll();
    omvormenProjectTypes();
}

A @PostConstruct 方法直接在 bean的构造和所有托管属性和依赖注入之后调用。您可以在其中执行与EJB相关的初始化作业。以下将在幕后发生：

A @PostConstruct method is called directly after bean's construction and all managed property and dependency injections. You can do your EJB-dependent initializing job in there. The following will then happen behind the scenes:

OverzichtAlle overzichtAlle = new OverzichtAlle();
overzichtAlle.setEjbFacade(ejbFacade);
overzichtAlle.init();

请注意，方法名称无关紧要。但是，$ code> init（）是非常自我记录的。

Note that the method name doesn't matter. But init() is pretty self-documenting.

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