I know there are loads of questions on SO regarding this exact issue, but I couldn't find a solution to my problem. I'm trying to use a #ManagedProperty in JSF 2. I used the example from this page, but mine's not working:
#ManagedProperty("#{userSession}")
private UserSession userSession;
public void setUserSession(UserSession userSession) {
this.userSession = userSession;
}
Both the parent bean and the bean injected are session scoped. Both beans have the #ManagedBean attribute. No faces-config.xml declarations, no EJBs, no use of Spring. One thing I noticed from that example is that both the bean classes implement Serializable. Mine do not, and I'm not sure if that is making the difference.
When I use this code, I get a NullPointerException when I try to operate on userSession. However, I know a session exists, because when I use #BalusC's findBean convenience method, it works. One thing with this though, is that my code only works if I call userSession = findBean("userSession") inside the same method where I'm "doing stuff". If I initialize userSession in the bean's constructor, I get another NPE. Any ideas?
Related
I've tried every solution from a couple dozen google searches: getRequestMap, ElResolver, evaluateExpressionGet and so on. Nothing, absolutely nothing, works. I get null every time. Here is the relevant code:
#ManagedBean(name="readerBean")
#ViewScoped
public class ReaderBean implements Serializable {...
And in the PhaseListener:
public void beforePhase(PhaseEvent event) {
if (event.getPhaseId() == PhaseId.RESTORE_VIEW) {
ReaderBean r = null; //The Managed Bean
try {
FacesContext fctx = FacesContext.getCurrentInstance();
r=(ReaderBean) fctx.getExternalContext().getRequestMap().get("readerBean");
r=(ReaderBean) fctx.getELContext().getELResolver().getValue(fctx.getELContext(), null, "readerBean");
r=(ReaderBean) fctx.getApplication().getExpressionFactory().createValueExpression(fctx.getELContext(), "#{readerBean}", ReaderBean.class).getValue(fctx.getELContext());
r=(ReaderBean) fctx.getApplication().evaluateExpressionGet(fctx, "#{readerBean}", ReaderBean.class);
Nothing works!!!
As to the request map approach, it fails because a view scoped bean is not stored in the request scope. It's instead stored in the view scope. As to the other approaches, they fail because the view scoped bean is stored in the view and thus only available after the view has been restored. However, you're trying to get it before the view has been restored. This is a chicken-egg problem.
You need to revise your approach. Perhaps the bean needs to be a request scoped one? Perhaps the logic needs to be executed at a different phase? Perhaps the logic needs to be performed in the bean itself instead? Etc.
As the concrete functional requirement for which you thought that this is the right solution is unmentioned in the question, I can't point you in the right direction.
This question already has an answer here:
#SessionScoped bean looses scope and gets recreated all the time, fields become null
(1 answer)
Closed 6 years ago.
ello
I have 2 Managed beans, one View scoped, the other Session scoped. The View scoped bean is defined as
#ManagedBean
#ViewScoped
public class InvoiceController implements Serializable {
private static final long serialVersionUID = 1L;
#ManagedProperty(value="#{invoiceService}")
private InvoiceService invoiceService;
The session scoped bean as
#ManagedBean
#SessionScoped
public class InvoiceService implements Serializable{
I am using the session scoped bean to hold a flag used to decide if a panel should be rendered, when I run this through the debug I find that every time I call the method on the sesison bean, it is a new instance of the bean and therefore does not retain the value of my flag between requests.
What am I doing wrong?
That can happen if you have imported #SessionScoped from the javax.enterprise.context package instead of from the javax.faces.bean package. The former works on CDI #Named beans only, while the latter works on JSF #ManagedBean beans only.
A JSF #ManagedBean without any valid scope would default to #NoneScoped which means that it's newly constructed on every single EL expression referencing the bean, such as the #ManagedProperty. This explains the symptoms you're seeing.
I had a similar problem. I use a save-method in the view scoped bean that calls a method in the session scoped bean to update some values.
This is what I found out by debugging (excuse my non-Java-guru English):
When first loading the page, the instance number of the injected session bean was for example 111111.
But in the save-method (and all other methods called by an action like a commandButton or action listeners btw), suddenly the session bean was of another instance (say 222222).
Both instances 111111 and 222222 contained the very same values.
All methods I called now were done in the 222222 instance and it changed values in there as I wanted it. But the 111111 instance remained untouched and unchanged.
So 222222 was basically a deep(?) clone of 111111, and not even a copy.
But, after the save-method was done and the page got reloaded, the original 111111 instance was used again in the view scope bean.
The 222222 instance just got thrown to the garbage.
My solution for this problem:
I'm not using the ManagedProperty injection anymore.
Instead I made some helper code to get the session bean wherever I need it (aka in the view scoped bean methods):
public Object getSessionBean(String sessionBeanName)
{
return FacesContext.getCurrentInstance().getApplication().getELResolver().getValue(FacesContext.getCurrentInstance().getELContext(), null, sessionBeanName);
}
For your example above, the call would be:
InvoiceService invoiceService = (InvoiceService) helper.getSessionBean("invoiceService");
Call it in your methods, do not store it as a field in the view scoped bean.
I hope this somehow helps you fix your problem.
We are currently moving from JSF-ManagedBeans to CDI. Unfortunately we have made excessive use of the EL-Resolver in the past in order to gain static access to session scoped beans managed by JSF.
Since CDI dependency injection is not available everywhere I rewrote the existing static lookup to make use of the BeanManager (Using SEAM-Solder extending BeanManagerAware).
Iterator<Bean<?>> iterator = beans.iterator();
Bean<T> bean = (Bean<T>) iterator.next(); // possible NPE, I know :)
CreationalContext<T> creationalContext = beanManager.createCreationalContext(bean);
T contextual = (T) beanManager.getReference(bean, type, creationalContext);
return contextual;
The code works and returns a container managed instance of the desired bean. BUT: the methods annotated with #PostConstruct do not get called using getReference(). Perhaps you guys know how to do it. Couldn't find anything googling the issue :-/
Best regards!
You should be using Application#evaluateExpressionGet() for this. Not only for CDI beans, but actually also for JSF beans you previously had.
FacesContext context = FacesContext.getCurrentInstance();
Bean bean = (Bean) context.getApplication().evaluateExpressionGet(context, "#{beanName}", Bean.class);
// ...
Much cleaner, however, is to just use CDI's #Inject or JSF's #ManagedProperty instead.
See also:
Get JSF managed bean by name in any Servlet related class
I have been developing my web-app using JPA 2.0 implementation EclipseLink 2.2.0. I finally got around to running multi-threaded code and I got this exception:
java.lang.IllegalStateException: Attempting to execute an operation on a closed EntityManager.
The objects that have all the javax.persistence calls in my application are defined as application scoped, like this:
#Model
#ApplicationScoped
public class LocationControl implements Serializable {
#PersistenceContext private EntityManager em;
#Resource private UserTransaction utx;
// etc
And of course all the managed beans (usually RequestScoped or ConversationScoped) that want to access the data base do so like this:
#Inject private LocationControl lc;
So my question is this: Did I get that Exception through the use of #ApplicationScoped DAO? I had thought that it would be more efficient that way, since the container would not have to be continually re-creating this object on every request if it did not have a scope, and the DAO has no state of its own. However if the EntityManager and UserTransaction object have to be separate instances for each user, then that would be a problem.
Alternatively, I could use syncrhonized on the DAO methods, but I think that would cause thread lockups in the container (GlassFish).
Any advice appreciated.
#Model annotation was originally created to annotate request scoped beans, here is how it's defined:
#Named
#RequestScoped
#Stereotype
#Target({TYPE, METHOD, FIELD})
#Retention(RUNTIME)
public #interface Model {}
You can of course override '#RequestScoped' with another annotation but '#ApplicationScoped' it's not a good choice as everyone in the application would modify the state of the same injected EntityManager. I think it would be best to leave it #RequestScoped in most cases, sometimes, for example for a login/logout data bean '#SessionScoped' could be an option but I cannot see a scenario for '#ApplicationScoped' dao.
If you don't want to use #Model at all and you use full Java EE container, then the stateless EJB ,as BalusC said, would be a great option for Dao too.
I'm working with JSF 2.0
I have a form in my admin section where I am going to select some users in a list.
The form (selectusers.xhtml) is adding these users to a list in a bean (SelectUsers.java).
After I have selected some user(s), I will pass the list of the user(s) from SelectUsers.java to another bean (AddAddressBean.java) and continue add information in another form (addadress.xhtml) which set other properties related to AddAddressBean for each user.
I do not know how to implement it. I would like that AddAddressBean.java shall be independent (so I can use it together with other beans), so I prefer that AddAddressBean.java shall not know about other beans.
Can you please help me? =)
B.R Carl
Several quick things come to mind :
Perhaps you could have a single bean only for those related pages, using #SessionScoped or the shorter CDI's #ConversationScope, or and this is the best of the three, the DeltaSpike #ViewAccessScoped
When clicking the button on page 1 where it'll take you to page 2, in the 1st bean, you can make use of Flash object to store objects you want to pass, and in the second bean's #PostConstruct method, you could get all the objects from the Flash object
If you dont mind using session scope, you can still have 2 beans, and one bean can refer to another bean using the jsf way(#ManagedProperty), or the Java EE inject way(#Inject) or the spring way if you use spring (#Autowired)
This how i implemented (used ConversationScoped as #bertie said ).
bean 1:
#Named("conversationBean1")
#ConversationScoped
public class ConversationBean1 implements Serializable {
//---start conversation----
}
bean 2:
#Named("conversationBean2")
#ConversationScoped
public class ConversationBean2 implements Serializable
{
#Inject
private ConversationBean1 conversationBean1;
}