I have a Bean ,with a #ManagedBean annotation, defined like this :
#ManagedBean
#SessionScoped
public class Bean implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
}
Now, I have another bean defined like this :
public class FooBean extends Bean {
// properties, methods here ...
}
When I try to reference FooBean in my JSF page, I have the following error :
Target Unreachable, identifier 'fooBean' resolved to null
Why JSF doesn't see FooBean as a managed bean ?
The point Alex is trying to make is that you're confusing classes with instances. This is a classic (pun intended) OOP mistake.
The #ManagedBean annotation does not work on classes per-se. It works on instances of such classes, defining an instance that is managed.
If your bean is defined like this:
#ManagedBean
#SessionScoped
public class MyBean implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
}
Then it means you have a session-scoped instance, called myBean (or whatever you want to name it).
Therefore, all classes that are subclasses of the MyBean class are not managed by default. Furthermore, how does JSF recognize where you're using the subclasses? If so, what names are you giving to those instances? (Because you have to give them some name, otherwise, how would JSF manage them?)
So, let's say you have another class:
Class MyOtherClass {
private MyBean myBeanObject; // myBeanObject isn't managed.
}
what happens to the #PostConstruct and all the other annotations you used? Nothing. If you created the instance of MyBean, then it's YOU who manages it, not JavaServerFaces. So it's not really a managed bean, just a common object that you use.
However, things change completely when you do this:
#ManagedBean
#SessionScoped
Class MyOtherClassBean {
#ManagedProperty("#{myBean}")
private MyBean myBeanObject;
public void setMyBeanObject(...) { ... }
public MyBeanClass getMyBeanObject() { ... }
}
Then again, what is managed is not the class, but the instance of the class. Having a ManagedBean means that you only have one instance of that bean (per scope, that is).
do you need BaseBean to be a managed bean? Since you name it BaseBean, I assume that this bean hold commonality between all your other managed bean. If so then it should not contain #ManagedBean annotation. Do this
public abstract BaseBean{
//...
}
Then inside your managed bean
#ManagedBean
#RequestScoped
public class FooBean extends BaseBean{
//...
}
Related
I have a parameterized class that implements the FactoryBean interface:
public class DogFactory<T extends Dog> implements FactoryBean<T> {
// ...
}
What I want is to use this factory for spawning objects of different classes (all of these classes extend Dog). So I imagined that I could do something like the following:
public class ShepherdService {
private DogFactory<Shepherd> shepherdFactory;
public ShepherdService(
#Autowired
DogFactory<Shepherd> shepherdFactory
) {
this.shepherdFactory = shepherdFactory;
}
// ...
}
Alas, I get the following error: Couldn't autowire. No beans of DogService<Shepherd> type found. :-(
How to inject it and use as DogFactory<Shepherd> or DogFactory<Corgi> (not just DogFactory)?
And another question. I also need to pass the Shepherd.class (or Corgi.class) to this bean, so it could "know" at run-time, objects of what exactly class should it produce. Is there a way to do that?
Or should I forget about FactoryBean and instantiate the factory as a regular class? Of course, I could do it this way:
DogFactory<Shepherd> shepherdFactory = new DogFactory<Shepherd>(Shepherd.class);
It would work perfectly, but I'd like to use FactoryBean as I use it for other factories in this project, so I would like to stick to FactoryBean.
Thanks in advance!
Update 1
Maybe I should clarify it more precise. What I need is a factory that could produce objects of different classes. All these classes should be extensions of the certain class (e.g., Shepherd and Corgi - all these classes extend Dog). And as the final result I actually need something like that:
public class DogService<T extend Dog> {
private DogFactory<T> dogFactory;
#Autowired
public DogService(DogFactory<T> dogFactory) {
this.dogFactory = dogFactory;
}
public T spawnDog(Color color) {
T dog = DogFactory.getObject(color);
return dog;
}
}
But it seems that I can't make a "universal" factory with the FactoryBean interface, so I can't do something like that:
public class DogFactory<T extends Dog> implements FactoryBean<T> {
// ...
}
Instead of that I have to do something like the following:
public class ShepherdFactory implements FactoryBean<Shepherd> {
// ...
}
public class CorgiFactory implements FactoryBean<Corgi> {
// ...
}
Is that true?
Thanks!
What I want is to instantiate this factory in another class
If you mean "having the factory injected in the class instead of the bean it creates", you could inject the factory by prefixing its name with an ampersand:
public class ShepherdService {
private DogFactory<Shepherd> shepherdFactory;
#Qualifier("&dogFactory")
public ShepherdService(DogFactory<Shepherd> shepherdService) {
this.shepherdService = shepherdService;
}
}
From the Spring documentation (section 3.8.3):
When you need to ask a container for an actual FactoryBean instance
itself, not the bean it produces, you preface the bean id with the
ampersand symbol & (without quotes) when calling the getBean method of
the ApplicationContext. So for a given FactoryBean with an id of
myBean, invoking getBean("myBean") on the container returns the
product of the FactoryBean, and invoking getBean("&myBean") returns
the FactoryBean instance itself.
Furthermore, my guess is that the FactoryBean is not picked up as a Spring bean as your snippets did not contain an XML config section, a Java config section, or a #Component annotation. I would explicitly declare the factory bean in a #Configuration annotated class, or annotate the factory class with #Component.
[edit]
But it seems that I can't make a "universal" factory with the
FactoryBean interface, so I can't do something like that:
You could still have a single Configuration class in which you declare all the factory beans.
#Configuration
public class DogFactoryConfig {
#Bean
public DogFactory<Shepherd> shepherdFactory() {
return new DogFactory<Shepherd>();
}
#Bean
public DogFactory<Corgi> corgiFactory() {
return new DogFactory<Corgi>();
}
}
And remove the #Component annotation from your DogFactory if it is present.
This is my current scenario:
#WebListener
public class WebListenerService implements HttpSessionListener{
.... implement methods
#Produces
#Dependent
public SessionDependentService sessionDependentService(){
}
}
#SessionScoped
#Named
public class AccountController implements Serializable{
//Injected properly and works as expected
#Inject
private SessionDependnetService sessionDependentService;
#Inject
#OnLogin
private Event<Account> accountEvent;
public void onLogin(){
accountEvent.fire(authenticatedAccount);
}
}
#SessionScoped
public class AccountObserver implements Serializable{
//This does not work. It is always null.
#Inject
private SessionDependnetService sessionDependentService;
public void onLoginEvent(#Observes #OnLogin final Account account) {
//When this methods is invoked
//the sessiondependentservice is always null here.
}
}
In the AccountController, the SessionDependentService is correctly injected and is not null, while in the AccountObserver, it is always null.
EDIT:
Event using the parameter injection still results to a null value.
public void onLoginEvent(#Observes #OnLogin final Account account, final SessionDependnetService sessionDependentService) {
//When this methods is invoked
//the sessiondependentservice is always null here.
}
Netbeans correctly highlights this as an injection point.
Why is this the case?
I am using wildfly 8 server.
I changed the producer bean from SessionScoped to Stateless bean:
#Stateless
public class WebListenerSessionService {
//Use Instance since http session are dynamic.
#Inject
private Instance<HttpSession> httpSession;
#Produces
#Dependent
public SessionDependentService sessionDependentService(){
//use session to lookup existing service or produce a new one.
}
}
Even though this works fine, there is no where in the CDI spec which says Producer method must be session beans.
to quote:
A producer method must be a default-access, public, protected or private, non-abstract method
of a managed bean class or session bean class. A producer method may be either static or non-
static. If the bean is a session bean, the producer method must be either a business method of
the EJB or a static method of the bean class.
And since #SessionScoped is a managed bean class, why would it an injection into an observer bean not work.
I would like to have a singleton bean instance by generic parameter based on a single #Component generic class.
(I am using Spring 4.)
My code :
I have an interface like this :
public interface Mapper<I, O> {
...
}
And multiple implementation of it which are Spring #Components (singletons). Something like this :
#Component
public class MapperA implements Mapper<ClazzAI, ClazzAO> {
...
}
and
#Component
public class MapperB implements Mapper<ClazzBI, ClazzBO> {
...
}
where ClazzAI, ClazzAO, ClazzBI and ClazzBO are basic Java classes.
I have another Spring #Component (singleton) which have a Mapper class as a generic parameter :
#Component
public class TransformerImpl<I, O, M extends Mapper<I, O>> {
/** The Mapper */
protected final M mapper;
#Inject
private TransformerImpl(final M mapper) {
this.mapper= mapper;
}
...
}
and I would like to use it like this :
#Inject
private TransformerImpl<ClazzAI, ClazzAO, MapperA> transformerA;
#Inject
private TransformerImpl<ClazzBI, ClazzBO, MapperB> transformerB;
The problem :
But Spring is not able to instantiate those 2 objects because it founds 2 implementations of Mapper : MapperA and MapperB even if I specify which implementation I want as a generic parameter.
Any idea how to make it without the need of instantiate all of those beans in a #Configuration class ?
You're asking for a singleton but requiring two injection points
#Inject
private TransformerImpl<ClazzAI, ClazzAO, MapperA> transformerA;
#Inject
private TransformerImpl<ClazzBI, ClazzBO, MapperB> transformerB;
for differently constructed objects. That doesn't make much sense.
You now realize you need two beans. If you can't (don't want to) do it in a #Configuration class with #Bean factory methods, you'll need to declare (and scan) two separate #Component classes. (I made your parent constructor public here.)
#Component
class MapperATransformerImpl extends TransformerImpl<ClazzAI, ClazzAO, MapperA> {
#Inject
public MapperATransformerImpl(MapperA mapper) {
super(mapper);
}
}
#Component
class MapperBTransformerImpl extends TransformerImpl<ClazzBI, ClazzBO, MapperB> {
#Inject
public MapperBTransformerImpl(MapperB mapper) {
super(mapper);
}
}
When processing the injection target
#Inject
private TransformerImpl<ClazzAI, ClazzAO, MapperA> transformerA;
Spring will find the MapperATransformerImpl, which is of type TransformerImpl<ClazzAI, ClazzAO, MapperA> and inject that.
Try with Spring 4. See Using generics as autowiring qualifiers
Edit
Like #SotiriosDelimanolis explained in his answer, Spring 4 can use type parameter information as qualifiers to select which bean definition matches a particular injection point, but in the end, it will only match against bean definition with concrete type definitions. In your case, the problem is that you need a TransformerImpl bean definition for each concrete type you want to inject.
As an alternative to defining all bean definition explicitly, check my answer to Spring autowiring issues on paramaterized class
#Named("myUniqueName")
public class ReportDashboardDao implements DashboardDAO{
//STUFF
}
how can i access the string inside #Named tag when i am injecting DashboardDAO like this :
#Named
public class DshboardDaoConsumer(){
#Inject List<DashboardDAO> dashboardDAO;
//STUFF
}
Use a Map instead
#Inject
Map<String, DashboardDao> dashBoardDaos;
This will inject a Map with bean names as keys and daos as values.
Of course, you could also read the annotation value from class instances.
You can't. You're injecting by type. After injection has been done, Spring does not leave behind any relation between the bean's object and the bean's name.
You might want to check out ApplicationContext#getBeanNamesByType() depending on what you want to do.
By implementing BeanNameAware.
#Named("myUniqueName")
public class ReportDashboardDao implements DashboardDAO, BeanNameAware{
//STUFF
private String beanName;
#Override
public Void setBeanName(String beanName) {
this.beanName = beanName;
}
}
So that Spring can inject the beanName into the bean. If you add a public String getBeanName(); in your DashboardDAO interface, DashboardDaoConsumer will be able to obtain it.
In this particular case, Spring will inject the name you specified in the annotation.
In my managedBean, fileUpload : Am calling other beans using #ManagedProperty as shown in code, now later in my class i have something like rtParser.getQuote() but it throws NullPointerException, my question is:
How can I initialize rtParser in this class?
#ManagedProperty(value = "#{rtParser}")
private PositionParserRT rtParser;
public PositionParserRT getRtParser()
{
return rtParser;
}
public void setrtParser(PositionParserRT rtParser)
{
this.rtParser = rtParser;
}
Updated
I am having similar kind of issue here and would highly appreciate any suggestions.
The way as you use #ManagedProperty expects the PositionParserRT to be a #ManagedBean too. So put that annotation on the class.
#ManagedBean
#SomeScoped // TODO: Choose the suitable scope.
public class PositionParserRT {
// ...
}
But if that class is already not a JSF managed bean in the first place (i.e. it has nothing do to with JSF views/models), then you're probably looking for the solution in the wrong direction. If it's a business service, rather make it a #Stateless EJB and inject it by #EJB instead.
#Stateless
public class PositionParserRT {
// ...
}
with
#EJB
private PositionParserRT rtParser;