I have an app managed by maven with two modules: one for persistence, and another for the webapp itself (gwt).
My tests in persistence module works like a charm, but, in webapp, when I execute the same method multiple times I got a java.lang.IllegalStateException: Attempting to execute an operation on a closed EntityManager..
I use guice-persist to inject the entity manager into my DAOs, and all my DAO methods have the #Transactional annotation.
In my webapp, I put a:
public class ScuvServletModule extends ServletModule {
#Override
protected void configureServlets() {
super.configureServlets();
install(MyPersistenceAPI.getModule()); // return my module and install it
filter("/*").through(PersistFilter.class);
/// another bindings...
}
}
If I remove the PersistFilter, it wotks, but randomly throws a Transaction Closed exception or something like that.
Any help?
I found the problem. It is the PersistFilter. Aparently, its a Singleton, my DAOs are singletons too, but the EntityManager isnt.
So, now I inject a Provider<EntityManager> instead EntityManager, and it works just like a charm.
Related
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 have below maven dependency & configuration set up
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
#Configuration
#EnableMongoAuditing
public class MongoConfig {
#Bean
MongoTransactionManager transactionManager(MongoDbFactory mongoDbFactory) {
return new MongoTransactionManager(mongoDbFactory);
}
}
Updated: I've taken the suggested solution to create a bean with #Transactional, and have it injected into my test class. Below is the service bean I created:
#Service
#Transactional
#RequiredArgsConstructor
public class MongoTransactionService {
private final UserRepo userRepo;
public void boundToFail() throws RuntimeException {
userRepo.save(User.builder().id("1").build());
throw new RuntimeException();
}
}
and test class where I inject a bean of MongoTransactionService:
#DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class,
includeFilters = #ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, classes = MongoTransactionService.class))
#ExtendWith(SpringExtension.class)
class MongoTransactionServiceTest {
#Autowired
UserRepo userRepo;
#Autowired
MongoTransactionService mongoTransactionService;
#Test
void testTransactional() {
try {
mongoTransactionService.boundToFail();
} catch (Exception e) {
// do something
}
val user = userRepo.findById("1").orElse(null);
assertThat(user).isNull();
}
}
I am expecting a call to boundToFail(), which throws a RuntimeException, would roll back the saved user, but the user still gets persisted in the database after the call.
It turns out that #DataMongoTest doesn't activate the auto-configuration for MongoDB transactions. I've filed a ticket with Spring Boot to fix that. In the mean time, you can get this to work by adding
#ImportAutoConfiguration(TransactionAutoConfiguration.class)
to your test class.
Note that using MongoDB transactions requires a replica set database setup. If that's not given the creation of a transaction will fail and your test case will capture that exception and the test will still succeed. The data will not be inserted but that's not due to the RuntimeException being thrown but the transaction not being started in the first place.
The question previously presented a slightly different code arrangement that suffered from other problems. For reference, here's the previous answer:
#Transactional needs to live on public methods of a separate Spring bean as the transactional logic is implemented by wrapping the target object with a proxy that contains an interceptor interacting with the transaction infrastructure.
You example suffers from two problems:
The test itself is not a Spring bean. I.e. there's no transactional behavior added to boundToFail(…). #Transactional can be used on JUnit test methods but that's controlling the transactional behavior of the test. Most prominently, to roll back the transaction to make sure changes to the data store made in the test do not affect other tests. See this section of the reference documentation.
Even if there was transactional logic applied to boundToFail(…), a local method call to the method would never trigger it as it doesn't pass the proxy that's applying it. See more on that in the reference documentation.
The solution to your problem is to create a separate Spring bean that carries the #Transactional annotation, get that injected into your test case and call the method from the test.
I am trying to use a #Transactional method inside a CDI class, instead of an EJB:
#javax.inject.Named
// fails #javax.enterprise.context.ApplicationScoped
// fails #javax.enterprise.context.SessionScoped
// works #javax.ejb.Singleton
// works #javax.ejb.Stateless
public class SomeClass {
#javax.persistence.PersistenceContext
private EntityManager em;
#javax.annotation.PostConstruct
#javax.transaction.Transactional
public void someMethod() {
em.persist(someEntity);
}
}
When I annotate SomeClass with #Singleton or #Stateless, everything works.
When I annotate SomeClass with #ApplicationScoped or #SessionScoped, WildFly 13 displays the following error message:
Transaction is required to perform this operation (either use a transaction or extended persistence context)
I was under the impression that #Transactional works with CDI since Java EE 7. Have I been mistaken? Or am I simply missing some additional configuration?
I'll try to give a short list of things to look when trying to make #Transactional work with CDI, so as to give the answer a bit more value than the comment:
We are discussing javax.transaction.Transactional, not javax.ejb.TransactionAttribute, which works for EJBs!
It does NOT work out-of-the-box in non-JEE applications!
And by JEE applications we mean those running a full JEE application server; Tomcat out-of-the-box does NOT support it!
Beware of classpath problems, specifically make sure no jar containing the annotation javax.transaction.Transactional exists e.g. in WEB-INF/lib, when running in a full JEE application server. If you want to utilize it in a non-full-JEE environment, you will need to have it in the classpath.
#Transactional is implemented as a CDI interceptor by the latest JTA specifications. As such:
It's not there in JEE < 7!
It has the same limitations as any interceptor. E.g. it cannot be called for initializer methods - #PostConstruct [THIS WAS THE PROBLEM IN THIS QUESTION], and it is NOT activated when invoking methods of this object, BEWARE!!!
I am quite confident that more errors may exist!!!
It feels so simple:
I have a ViewScoped bean (JPA2 + EE6 + Seam3, if that matters) where the user of the web application can invoke a method like this:
public void save() {
doEntityManagerStuff(); // manipulates data in the database
callRemoteWebservice(); // which is to read said data and propagate it to other systems
}
Unfortunately, save() starts a transaction at the opening curly bracket and doesn't commit it before the closing bracket, meaning that the new data is not available to the remote web service to read.
I have tried to explicitly extract and annotate the database work:
#TransactionAttribute(REQUIRES_NEW)
private void doEntityManagerStuff() {
blabla(); // database stuff
}
But that didn't have any impact at all. (Maybe because that's EJB stuff and I'm running on seam...?)
The only thing that worked for me so far was to inject #UserTransaction and force commit the transaction at the end of either save() or doEntityManagerStuff() but that felt incredibly dirty and dangerous.
The other alternative would be to turn off container-managed transactions for the entire project, but that means I'd have to make all my beans manage their transactions manually, just so I can make this one case work.
Is there a better way?
To answer my own question:
I only went half-way, and that's why it didn't work. I didn't know enough about EJBs and their boudaries, and naively though just annotating the doEntityManagerStuff(...) method with a transaction attribute in my view-scoped CDI/Seam bean would be enough.
It isn't.
When I moved said method into a separate, stateless EJB, injected that into my CDI/Seam bean and called it from there, everything worked as expected.
#Stateless
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public class MyPersister {
...
public void doEntityManagerStuff() {
blabla(); // database stuff
}
...
}
and
#ViewScoped
public class MyWebsiteBean {
...
#Inject MyPersister persister;
...
public void save() {
persister.doEntityManagerStuff(); //uses its own transaction
callRemoteWebService();
}
...
}
Looking at this answer, it says:
If you don't want to use an Application Client Container and instead just run the application client class through a java command, injection won't be possible and you'll have to perform a JNDI lookup.
However, given that I am trying to inject a DAO bean like the example shown here, if I cannot do the automatic injecting, it means my application must manually do the JNDI lookup and all the transaction begin/end that I would get for free if the #EJB actually worked.
However, since everything is all within the same Eclipse EJB Project (it also failed with the same null handle when I had my client code in a Dynamic Web Project), surely there must be an easy way to get it all working? Can anyone suggest what I am doing wrong?
Finally, this article suggests that DAOs are not needed, but if I replace within my EJB:
#EJB MyDao dao;
with the more direct:
#PersistenceContext private EntityManager em;
I still get the similar null value; is this the same injection failure problem?
NB: I have just noticed this answer:
This is a bug in Glassfish (apparently in the web services stack).
I am running v4.0 Build 89, which still has this bug? Does this mean I have to do all JPA actions the long-winded way?
I eventually found out that the problem/issue is that in order to use injection of the #PersistenceContext the class MUST be a bean itself. This is hinted at in the example on Wikipedia:
#Stateless
public class CustomerService {
#PersistenceContext
private EntityManager entityManager;
public void addCustomer(Customer customer) {
entityManager.persist(customer);
}
}
I could delete this question, but perhaps leaving this answer might provide a hint to someone, or at least show them a minimal working example of EJB and JPA.