[英]How to inject a http session attribute to a bean using CDI
I have some legacy code that put objects as http session attributes using code like this: 我有一些遗留代码,使用如下代码将对象作为http会话属性:
MyObject object = new MyObject();
Map<String, Object> sessionMap = FacesContext.getCurrentInstance().getExternalContext().getSessionMap();
sessionMap.put("attrname", object);
The old facelets accessed the code using 旧的facelets使用了访问代码
@ManagedProperty("#{attrname}")
private MyObject object;
Is there any way using CDI ( @Inject
) to inject this session attribute to a Bean? 有没有办法使用CDI(
@Inject
)将此会话属性注入Bean?
In new code that uses CDI what's the better way to create and inject objects that need to be created in a controlled way. 在使用CDI的新代码中,创建和注入需要以受控方式创建的对象的更好方法是什么。
Get hold of it in a session scoped managed bean with a @Produces
@Named
on the getter. 在getter上使用
@Produces
@Named
在会话范围的托管bean中获取它。
@SessionScoped
public class MyObjectProducer implements Serializable {
private MyObject myObject;
@Produces
@Named("attrname")
public MyObject getMyObject() {
return myObject;
}
public void setMyObject(MyObject myObject) {
this.myObject = myObject;
}
}
When you set it somehow via eg myObjectProducer.setMyObject(myObject)
elsewhere (or perhaps a CDI @Observes
event), then you can inject it anywhere using @Inject @Named
. 当你以某种方式通过例如
myObjectProducer.setMyObject(myObject)
在其他地方(或者可能是CDI @Observes
事件)设置它时,你可以使用@Inject @Named
将它注入任何地方。
@Inject
@Named("attrname")
private MyObject myObject;
And yes, it's still available via #{attrname}
in EL the usual way. 是的,它仍然通过EL中的
#{attrname}
以通常的方式提供。 And no, it won't be auto-created when not set, it'll remain null
until you actually set it as a property of the producer class. 不,它不会在未设置时自动创建,它将保持为
null
直到您实际将其设置为生产者类的属性。
Alternatively, if you really intend to keep the legacy way of setting the instance via ExternalContext#getSessionMap()
(eg because it's third party and you can thus not change it), then you can alternatively also let the producer return it directly from the session map: 或者,如果您真的打算通过
ExternalContext#getSessionMap()
继续设置实例的遗留方式(例如因为它是第三方而您不能更改它),那么您也可以让生产者直接从会话中返回它地图:
@SessionScoped
public class MyObjectProducer implements Serializable {
@Produces
@Named("attrname")
public MyObject getMyObject() {
return (MyObject) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("attrname");
}
}
This however isn't guaranteed to work when injected in a non-JSF artifact, such as an arbitrary @WebServlet
, as the FacesContext#getCurrentInstance()
would obviously return null
. 但是,当注入非JSF工件(例如任意的
@WebServlet
,这并不能保证工作,因为FacesContext#getCurrentInstance()
显然会返回null
。
This is the way to go, for both non-jsf and jsf artifacts. 这是非jsf和jsf工件的方法。
@Qualifier
@Retention(RUNTIME)
@Target({TYPE,METHOD,FIELD,PARAMETER});
public @interface SessionAttribute {
@NonBinding
String value() default "";
}
@ApplicationScope
public class SessionAttributeService {
//Dont worry, this is a proxy, and CDI will ensure that the right one called at the right time.
@Inject
private HttpServletRequest servletRequest;
@Produces
@SessionAttribute
@RequestScope
public String sessionAttribute(final InjectionPoint ip){
final SessionAttribute sa = ip.getAnnotated().getAnnotation(SessionAttribute.class);
final HttpSession session = servletRequest.getSession();
return session.getAttribute(sa.value());
}
}
And use case: 用例:
@RequestScope
public class MyServiceBean {
@Inject
@SessionAttribute("theAttribute")
private String attribute;
}
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