I need to run some code when the FacesServlet starts, but as FacesServlet is declared final I can not extend it and overwrite the init() method.
In particular, I want to write some data to the database during development and testing, after hibernate has dropped and created the datamodel.
Is there a way to configure Faces to run some method, e.g. in faces-config.xml?
Or is it best to create a singleton bean that does the initialization?
Use an eagerly initialized application scoped managed bean.
#ManagedBean(eager=true)
#ApplicationScoped
public class App {
#PostConstruct
public void startup() {
// ...
}
#PreDestroy
public void shutdown() {
// ...
}
}
(class and method names actually doesn't matter, it's free to your choice, it's all about the annotations)
This is guaranteed to be constructed after the startup of the FacesServlet, so the FacesContext will be available whenever necessary. This in contrary to the ServletContextListener as suggested by the other answer.
You could implement your own ServletContextListener that gets notified when the web application is started. Since it's a container managed you could inject resources there are do whatever you want to do. The other option is to create a #Singleton ejb with #Startup and do the work in it's #PostCreate method. Usually the ServletContextListener works fine, however if you have more than one web application inside an ear and they all share the same persistence context you may consider using a #Singleton bean.
Hey you may want to use some aspects here. Just set it to run before
void init(ServletConfig servletConfig)
//Acquire the factory instances we will
//this is from here
Maybe this will help you.
Related
This post is related to an older SO Post of mine, wherein I was trying to understand the requirements of a no-args constructor by WELD.
Right now, I'm trying to figure out if there is a way in CDI to inject an #ApplicationScoped bean (#Normal) into a #Dependent scope. From what I've read from WELD, the requirements are to have a non-private no-arg constructor to be proxyable. However, I do not have control over the bean definition as it is provided by a library. My code is doing the following:
#Produces
#ApplicationScoped
#Named("keycloakAdmin")
public Keycloak getKeycloakAdminClient(#Named("keycloakDeployment") final KeycloakDeployment deployment) {
String clientId = deployment.getResourceName();
Map<String, Object> clientCredentials = deployment.getResourceCredentials();
// need to set the resteasy client connection pool size > 0 to ensure thread safety (https://access.redhat.com/solutions/2192911)
ResteasyClient client = new ResteasyClientBuilder().connectionPoolSize(CONNECTION_POOL_SIZE).maxPooledPerRoute(CONNECTION_POOL_SIZE)
.defaultProxy("localhost",8888)
.build();
KeycloakBuilder builder = KeycloakBuilder.builder()
.clientId(clientId)
.clientSecret((String) clientCredentials.get(CredentialRepresentation.SECRET))
.realm(deployment.getRealm())
.serverUrl(deployment.getAuthServerBaseUrl())
.grantType(OAuth2Constants.CLIENT_CREDENTIALS)
.resteasyClient(client);
return builder.build();
}
// error thrown here that cannot inject #Normal scoped bean as it is not proxyable because it has no no-args constructor
#Produces
#Dependent
#Named("keycloakRealm")
public RealmRepresentation getKeycloakRealm( #Named("keycloakAdmin") final Keycloak adminClient ){
// error thrown here that cannot inject #Normal scoped bean as it is not proxyable because it has no no-arg
return adminClient.realm(resolveKeycloakDeployment().getRealm()).toRepresentation();
}
The problem is that I do not control the Keycloak bean; it is provided by the library. Consequently, I have no way of providing a no-argument constructor to the bean.
Does this mean it is impossible to do? Are there any workarounds that one can use? This would seem like a significant limitation by WELD, particularly when it comes to #Produceing 3rd party beans.
My goal is to have a single Keycloak bean for the application as it is thread-safe and only needs to be initialized once. However, I want to be able to inject it into non-application-scoped beans.
There is a #Singleton scope which may address my issue, but if #Singleton works for this case, what is the purpose of the 2 different scopes? Under what circumstances would one want a non-proxied singleton (#Singleton) vs a proxied one (#ApplicationScoped)? Or is #Singleton for the entire container, whereas #ApplicationScoped for the application (WAR) only instead? How does it apply to an EAR or multiple ears?
First I'd like to clear out that I know what a NullPointerException is and how to handle that. My question is about how to access the #ApplicationScoped bean that is created on server startup, through the scheduler that I would like to run once a day. All I get now is a new bean, which is null at the beginning and not the already created bean.
The scheduler does the initiation of the bean so I end up with two beans, one that is updated by the scheduler (all the time) and one that is used when navigating in the web application.
So...
I have a web application with a #ApplicationScoped bean. This one is loaded from database on Tomcat startup.
This means that if something is changed in database in some other way than through the web application the changes won't be viewable until the Tomcat has been restarted.
So I thought I could make a Schedule to reload this #ApplicationScoped bean on a specific time during the day. The trouble is that I get a whole new #ApplicationScoped bean.
So how should I do to get the current bean updated and not a new one?
I've tried the solution in this tread: Refresh/Reload Application scope managed bean without any luck. My bean is still null.
I've also looked at the following threads without really solving my problem:
application scoped bean's view is not updated
Access ApplicationScoped bean through ServletContext
My ApplicationBean.java
import javax.enterprise.context.ApplicationScoped;
#Named(value = "applicationBean")
#ApplicationScoped
public class ApplicationBean {
#PostConstruct
public void init() {
//load variables from db
}
}
My ScheduleTaskConfig.java
#WebListener
public class ScheduleTaskConfig implements ServletContextListener {
private ScheduledExecutorService scheduler;
#Override
public void contextInitialized(ServletContextEvent event) {
Reloader reloader = new Reloader(event.getServletContext());
scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleAtFixedRate(reloader, 2, 3, TimeUnit.MINUTES);
}
#Override
public void contextDestroyed(ServletContextEvent sce) {
scheduler.shutdownNow();
}
}
My Reloader.java
public class Reloader implements Runnable {
private ServletContext context;
public Reloader(ServletContext context) {
this.context = context;
}
#Override
public void run() {
ApplicationBean applicationBean = (ApplicationBean) context.getAttribute("applicationBean");
if (applicationBean != null) {
applicationBean.init();
}
}
}
I just don't know what is wrong. I don't understand how to solve this.
I know I've written that the schedule should run every 3 minutes but when I get this to work the schedule should run once a day.
Is there a better way to do this or have I just forgotten something? I've googled the whole day without getting forward so I really need help.
Thank you.
Edited:
So my servlet context is up and my listener is notified before my application context is up?
What if I use the webpage then my application context is up (?) but my scheduler still doesn't work, the bean in the scheduler is still a new one and not the one I've been using when navigating in the web application. Or am I just confused over this? :)
Thank you for your help.
Edited:
I'm using Primefaces 6.0 and I suppose this bean is a JSF bean. Other beans used are Spring beans imported from a model class. Sorry for the confusion I have removed the Spring notation and added Primefaces instead.
I hope this clears things out. Thank you
I'm trying to get used to how JSF works with regards to accessing data (coming from a spring background)
I'm creating a simple example that maintains a list of users, I have something like
<h:dataTable value="#{userListController.userList}" var="u">
<h:column>#{u.userId}</h:column>
<h:column>#{u.userName}</h:column>
</h:dataTable>
Then the "controller" has something like
#Named(value = "userListController")
#SessionScoped
public class UserListController {
#EJB
private UserListService userListService;
private List<User> userList;
public List<User> getUserList() {
userList = userListService.getUsers();
return userList;
}
}
And the "service" (although it seems more like a DAO) has
public class UserListService {
#PersistenceContext
private EntityManager em;
public List<User> getUsers() {
Query query = em.createQuery("SELECT u from User as u");
return query.getResultList();
}
}
Is this the correct way of doing things? Is my terminology right? The "service" feels more like a DAO? And the controller feels like it's doing some of the job of the service.
Is this the correct way of doing things?
Apart from performing business logic the inefficient way in a managed bean getter method, and using a too broad managed bean scope, it looks okay. If you move the service call from the getter method to a #PostConstruct method and use either #RequestScoped or #ViewScoped instead of #SessionScoped, it will look better.
See also:
Why JSF calls getters multiple times
How to choose the right bean scope?
Is my terminology right?
It's okay. As long as you're consistent with it and the code is readable in a sensible way. Only your way of naming classes and variables is somewhat awkward (illogical and/or duplication). For instance, I personally would use users instead of userList, and use var="user" instead of var="u", and use id and name instead of userId and userName. Also, a "UserListService" sounds like it can only deal with lists of users instead of users in general. I'd rather use "UserService" so you can also use it for creating, updating and deleting users.
See also:
JSF managed bean naming conventions
The "service" feels more like a DAO?
It isn't exactly a DAO. Basically, JPA is the real DAO here. Previously, when JPA didn't exist, everyone homegrew DAO interfaces so that the service methods can keep using them even when the underlying implementation ("plain old" JDBC, or "good old" Hibernate, etc) changes. The real task of a service method is transparently managing transactions. This isn't the responsibility of the DAO.
See also:
I found JPA, or alike, don't encourage DAO pattern
DAO and JDBC relation?
When is it necessary or convenient to use Spring or EJB3 or all of them together?
And the controller feels like it's doing some of the job of the service.
I can imagine that it does that in this relatively simple setup. However, the controller is in fact part of the frontend not the backend. The service is part of the backend which should be designed in such way that it's reusable across all different frontends, such as JSF, JAX-RS, "plain" JSP+Servlet, even Swing, etc. Moreover, the frontend-specific controller (also called "backing bean" or "presenter") allows you to deal in a frontend-specific way with success and/or exceptional outcomes, such as in JSF's case displaying a faces message in case of an exception thrown from a service.
See also:
JSF Service Layer
What components are MVC in JSF MVC framework?
All in all, the correct approach would be like below:
<h:dataTable value="#{userBacking.users}" var="user">
<h:column>#{user.id}</h:column>
<h:column>#{user.name}</h:column>
</h:dataTable>
#Named
#RequestScoped // Use #ViewScoped once you bring in ajax (e.g. CRUD)
public class UserBacking {
private List<User> users;
#EJB
private UserService userService;
#PostConstruct
public void init() {
users = userService.listAll();
}
public List<User> getUsers() {
return users;
}
}
#Stateless
public class UserService {
#PersistenceContext
private EntityManager em;
public List<User> listAll() {
return em.createQuery("SELECT u FROM User u", User.class).getResultList();
}
}
You can find here a real world kickoff project here utilizing the canonical Java EE / JSF / CDI / EJB / JPA practices: Java EE kickoff app.
See also:
Creating master-detail pages for entities, how to link them and which bean scope to choose
Passing a JSF2 managed pojo bean into EJB or putting what is required into a transfer object
Filter do not initialize EntityManager
javax.persistence.TransactionRequiredException in small facelet application
It is a DAO, well actually a repository but don't worry about that difference too much, as it is accessing the database using the persistence context.
You should create a Service class, that wraps that method and is where the transactions are invoked.
Sometimes the service classes feel unnecessary, but when you have a service method that calls many DAO methods, their use is more warranted.
I normally end up just creating the service, even if it does feel unnecessary, to ensure the patterns stay the same and the DAO is never injected directly.
This adds an extra layer of abstraction making future refactoring more flexible.
I'm currently writing a library where I want the user of my library to implement an interface. From within my library I'm calling this implementation.
I'm using ServiceLoader to instantiate the implementation provided by the integrator and it works just fine. The integrator calls a start() method in my library and in the end he gets something in return. The implementation is used to give me some things along the way that I need in order to get to the final result.
(I'm deliberately not using CDI or any other DI container 'cause I want to create a library that can be used anywhere. In a desktop application, a spring application an application using guice...)
Now I'm facing a problem. I'm creating a showcase in which I'm using my own library. It's a webapplication where I'm using jsf and CDI. When I instantiate the implementation provided in said webapp from within my library, I'm dealing with a non-container managed object. But since this implementation needs to use container managed objects I'm kinda screwed since this can never work.
Example:
Interface in lib:
public interface Example{
public abstract String getInfo();
}
Implementation in war:
public class ExampleImpl implements Example{
#Inject
private ManagedBean bean;
public String getInfo(){
return bean.getSomethingThatReturnsString();
}
}
As you can see this is a huge problem in the way my library is build since the bean will always be null... This means no one using a DI container can use my library. I know I can get the managedbean by doing a FacesContext lookup and get the managedbean but more importantly, my library isn't very well designed if you think about it.
So to conclude my question(s):
Is there any way I can make the serviceloader use a DI container to instantiate the class?
Anyone who knows a better way to fix my problem?
Anyone who knows a better way to get the things I need without making the integrator implement an interface but I can get information from the integrator?
I know this is a quite abstract question but I'm kinda stuck on this one.
Thanks in advance
As the implementation of Example is not performed within the CDI container the injection doesn't happen. What you can do is to lookup the bean manually using the BeanManager. According to the docs, the BeanManager is bound to the jndi name java:comp/BeanManager. Using the following code you can get the BeanManager within your implementation class and lookup the dependencies manually:
InitialContext context = new InitialContext();
BeanManager beanManager = (BeanManager) context.lookup("java:comp/BeanManager");
Set<Bean<?>> beans = beanManager.getBeans(YourBean.class, new AnnotationLiteral<Default>() {});
Bean<YourBean> provider = (Bean<YourBean>) beans.iterator().next();
CreationalContext<YourBean> cc = beanManager.createCreationalContext(provider);
YourBean yourBean = (YourBean) beanManager.getReference(provider, YourBean.class, cc);
where YourBean is the dependency you are looking for.
Continuing on my previous question, I'm trying to initialize a session-scoped JSF bean when the application's session first starts, so the bean will be available to a user, regardless of which page they access on my web application first. My custom listener:
public class MyHttpSessionListener implements HttpSessionListener {
#Override
public void sessionCreated(HttpSessionEvent se) {
if (FacesContext.getCurrentInstance().getExternalContext().getSessionMap()
.get("mySessionBean") == null) {
FacesContext.getCurrentInstance().getExternalContext().getSessionMap()
.put("mySessionBean", new MySessionBean());
}
}
}
However, this is giving me a stack overflow error. It appears that the put() method in the SessionMap class tries to create a new HttpSession, thus causing an infinite loop to occur with my listener. How can I initialize a JSF session-scoped bean when my application's session first starts, without running into this issue?
I'm using JSF 2 with Spring 3, running on WebSphere 7.
Thanks!
The session isn't been fully finished creating at that point. Only when the listener method leaves, the session is put into the context and available by request.getSession() as JSF's getSessionMap() is using under the covers.
Instead, you should be grabbing the session from the event argument and use its setAttribute() method. JSF lookups and stores session scoped managed beans just there and won't create a new one if already present.
public void sessionCreated(HttpSessionEvent event) {
event.getSession().setAttribute("mySessionBean", new MySessionBean());
}
Note that I removed the superfluous nullcheck as it's at that point impossible that the session bean is already there.
Unrelated to the concrete problem, you should actually never rely on the FacesContext being present in an implementation which isn't managed by JSF. It is quite possible that the session can be created during a non-JSF request.