I have a Managed Bean:
public class CategoriaManagedBean {
#EJB
private CategoriaBeanLocal categoriaBean;
private Categoria categoria;
private List<Categoria> menu;
}
In my constructor I try:
public CategoriaManagedBean() {
menu = categoriaBean.findByIdCategoriaPadre(0);
}
But I get a error "Cannot create the instance of the class", why can't I initialize the attribute in the constructor?
I fix the problem with:
#PostConstruct
public void init() {
menu = categoriaBean.findByIdCategoriaPadre(0);
}
But I want to know the reason and if I am doing well with #PostConstruct
Greetings.
Using #PostConstruct is the correct approach.
EJBs are injected after the constructor is invoked on a ManagedBean.
That's why there is a #PostConstruct annotation.
Here's the first line from the documentation:
The PostConstruct annotation is used on a method that needs to be executed after dependency injection is done to perform any initialization.
Related
I have a class (OmeletteMaker) that contains an injected field (Vegetable). I would like to write a producer that instantiates an injected object of this class. If I use 'new', the result will not use injection. If I try to use a WeldContainer, I get an exception, since OmeletteMaker is #Alternative. Is there a third way to achieve this?
Here is my code:
#Alternative
public class OmeletteMaker implements EggMaker {
#Inject
Vegetable vegetable;
#Override
public String toString() {
return "Omelette: " + vegetable;
}
}
a vegetable for injection:
public class Tomato implements Vegetable {
#Override
public String toString() {
return "Tomato";
}
}
main file
public class CafeteriaMainApp {
public static WeldContainer container = new Weld().initialize();
public static void main(String[] args) {
Restaurant restaurant = (Restaurant) container.instance().select(Restaurant.class).get();
System.out.println(restaurant);
}
#Produces
public EggMaker eggMakerGenerator() {
return new OmeletteMaker();
}
}
The result I get is "Restaurant: Omelette: null", While I'd like to get "Restaurant: Omelette: Tomato"
If you provide OmeletteMaker yourself, its fields will not be injected by the CDI container. To use #Alternative, don't forget specifying it in the beans.xml and let the container instantiate the EggMaker instance:
<alternatives>
<class>your.package.path.OmeletteMaker</class>
</alternatives>
If you only want to implement this with Producer method then my answer may be inappropriate. I don't think it is possible (with standard CDI). The docs says: Producer methods provide a way to inject objects that are not beans, objects whose values may vary at runtime, and objects that require custom initialization.
Thanks Kukeltje for pointing to the other CDI question in comment:
With CDI extensions like Deltaspike, it is possible to inject the fields into an object created with new, simply with BeanProvider#injectFileds. I tested this myself:
#Produces
public EggMaker eggMakerProducer() {
EggMaker eggMaker = new OmeletteMaker();
BeanProvider.injectFields(eggMaker);
return eggMaker;
}
The various #EnableXXXRepository annotations of Spring Data allow you to specify a custom base class for your repositories, which will be used as an implementation of methods in your repository.
If such a base class needs access to other beans in the ApplicationContext how does one get those injected? It doesn't work out of the box, because Spring Data instantiates those base classes itself, supporting only special store dependent constructor parameters.
Note: I created this answer in the chat to this now deleted question and thought it might be valuable for others, although the original question is gone.
In the #Enable...Repository annotation specify a repositoryBaseClass and repositoryFactoryBeanClass. Like this:
#EnableMongoRepositories(
repositoryBaseClass = MyBaseClass.class,
repositoryFactoryBeanClass = MyRepositoryFactoryBean.class)
In that RepositoryFactoryBean class, you can use normal dependency injection, because it is a Spring Bean, so, for example, you can get an instance of SomeBean injected via the constructor, as shown below:
public class MyRepositoryFactoryBean<T extends Repository<S, ID>, S, ID extends Serializable> extends MongoRepositoryFactoryBean<T,S,ID>{
private final SomeBean bean;
public MyRepositoryFactoryBean(Class repositoryInterface, SomeBean bean) {
super(repositoryInterface);
this.bean = bean;
}
}
Your RepositoryFactoryBean now create an instance of a custom RepositoryFactory by overwriting 'getFactoryInstance'.
#Override
protected RepositoryFactorySupport getFactoryInstance(MongoOperations operations) {
return new MyMongoRepositoryFactory(operations, bean);
}
While doing so, it can pass on the bean to be injected. bean in the example above.
And this factory finally instantiates your repository base class. Probably the best way to do it is to delegate everything to the existing factory class and just add injecting of the dependency to the mix:
public class MyMongoRepositoryFactory extends MongoRepositoryFactory {
private final SomeBean bean;
MyMongoRepositoryFactory(MongoOperations mongoOperations, SomeBean bean) {
super(mongoOperations);
this.bean = bean;
}
#Override
protected Object getTargetRepository(RepositoryInformation information) {
Object targetRepository = super.getTargetRepository(information);
if (targetRepository instanceof MyBaseClass) {
((MyBaseClass) targetRepository).setSomeBean(bean);
}
return targetRepository;
}
}
There is a complete working example on Github.
In my JSF application I'm using a #ViewScoped bean Publication to show/edit data coming from my database. In that bean there is a field for a subtype-specific data object, i.e. containing a different object depending on whether the publication is, say, a book or an article.
#ViewScoped
#Named
public class Publication implements Serializable {
#Inject
DatabaseStorage storage;
...
String id;
String type;
PublicationType typedStuff;
#PostConstruct
public void init() {
// Get an URL parameter from the request,
// look up row in database accordingly, initialize String "type".
switch (type) {
case "ARTICLE":
typedStuff = new Article(id);
break;
case "BOOK":
typedStuff = new Book(id);
break;
default:
break;
}
}
}
...with classes Article and Book that implement / extend PublicationType.
So far, so good, but I would like for typedStuff to be a CDI bean, so that I can inject useful resources there.
I've read this and this page on producer methods, as well as this tutorial and this very related SO question, but none of them answer precisely my question: Can I inject based on a field that the injecting bean itself only knows at runtime?
I've gotten the producer method to work as such, but I can't parametrize it, so I can't get that switch to work.
If I put the producer method in a separate class (or bean) then I don't have access to the type field.
If I inject the injecting bean into the producer class, or move the producer method into the injecting class, I get a circular injection.
If I put the producer method statically into the injecting class, I also don't have access, because type cannot be static. (Although, since it's only used momentarily...?)
Also (and that is probably the answer right there), the producer method is executed before my injecting bean's init method, so type wouldn't even have been set yet.
Does anybody have a better idea?
No you cannot, but you can select a bean based on the field value. Say:
public interface PublicationType {}
#PType("ARTICLE")
public class Article implements PublicationType{}
#PType("BOOK")
public class Book implements PublicationType {}
And define a qualifier:
public #interface PType {
String value();
}
And define an AnnotationLiteral:
public class PTypeLiteral extends AnnotationLiteral<PType> implements PType {}
Then you can use:
public class Publication {
#Any
#Inject
private Instance<PublicationType> publicationTypes;
public void doSomething() {
PType ptype = new PTypeLiteral(type);
// Of course you will have to handle all the kind of exceptions here.
PublicationType publicationType = publicationTypes.select(ptype).get();
}
}
There is the javax.inject.Provider interface (I think You are using #Named and #Inject annotations from the same package).
You could use it to achieve what You want. It will create instances for You with injected fields.
One drawback is that You will have to set the id yourself.
#ViewScoped
#Named
public class Publication implements Serializable {
#Inject
DatabaseStorage storage;
#Inject
Provider<Article> articleProvider;
#Inject
Provider<Book> bookProvider;
String id;
String type;
PublicationType typedStuff;
#PostConstruct
public void init() {
// Get an URL parameter from the request,
// look up row in database accordingly, initialize String "type".
switch (type) {
case "ARTICLE":
typedStuff = articleProvider.get();
typedStuff.setId(id);
break;
case "BOOK":
typedStuff = bookProvider.get();
typedStuff.setId(id);
break;
default:
break;
}
}
}
I am using jsf2.2 with wildfly 8.1 and javaee7.
My CDI bean injection in the phaselistener works as expected, but the #PostConstuct method is never invocked
I have tried to annotate the phaselistener with #javax.enterprise.context.ApplicationScope, SessionScope and Dependent to no avail.
Apart from naming, this is the exact thing i do in my post construct.
//#ApplicationScope
//#SessionScope
//#Dependent
public class MyPhaseListener implements PhaseListener {
#Inject
#Any
private Instance<MyOrderedUrlHandler> myOrderedUrlhandlers;
private Map<String, List<MyOrderedUrlHandler> orderedUrlHandlersMap;
#PostConstruct
void mapOrderedUrlHandlers() {
LOG.info("Executing postconstruct");
orderedUrlHandlersMap = Maps.newHashMap();
for(final MyOrderedUrlHandler urlhandler : myOrderedUrlhandlers) {
final String handles = urlhandler.url();
final List<MyOrderedUrlHandler> registeredHandlers = orderedUrlHandlersMap.get(handles);
if(registeredHandlers == null) {
registeredHandlers = Lists.newArraList();
}
registeredHandlers.add(urlHandler);
orderedUrlHandlersMap.put(handles, registeredHandlers);
}
}
}
Method level injection also works fine.
Is it the case that #PostConstruct callback is not part of jsf phaselistener specs?
According to section 5.4.1 of the JSF 2.2 spec, PhaseListener is not a managed bean but is injectable.
According to section 5.4.2, managed beans must support lifecycle annotations #PostConstruct and #PreDestroy.
Since a PhaseListener is not a managed bean in the sense of JSF, it does not follow from the spec that a phase listener implementation must support #PostConstruct.
I have two beans:
#Named
#SessionScoped
public class Session implements Serializable {
private String temp;
+getter, setter
}
#Named
#RequestScoped
public class Test {
#Inject
private Session s;
#PostConstruct
public void init() {
this.sth = s.getTemp(); //here is exception
}
}
When I try to fetch in init same value from session I get NullPointerException. What am I doing wrong? Server is JBoss eap 6.0, JSF v2.1. Thanks in advance
Edit: I investigated that problem appears only when I have more than 11 items in primefaces submenu component. If I have less than 11 items every thinks work OK. I am using PrimeFaces v 3.5.
Edit 2: On session bean only constructor is invoked. I have method annotated with PostConstruct but it is not called. I always get NullPointerException after invoking any method on session from Test bean.