Java
SpringBoot
1.SpringBoot : Error while saving User failed to lazily initialize a collection of role:address, could not initialize proxy - no Session
On Dec 2022, while implemeting Async save oprations after reading excel
I'm using an `@Async` annotation on a service layer method.
Everything works fine when I EAGERLY load @OneToMany collection fields, but when I try to access LAZY loaded element I found that Hibernate `SessionImplementor` object `session` is null. That obviously give me an exception:
```
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role:
....
```
Here is my collection field:
```
@OneToMany(mappedBy="abc", fetch=FetchType.LAZY, cascade=CascadeType.REMOVE)
@OrderBy(value="xsd asc")
@JsonIgnore
private Set- items = new HashSet
- ();
```
How can I bind hibernate session in order to LAZELY load my object inside `@Async` context?
**Solution**
had the same problem, spent few days trying to find a solution, finally got a solution. I would like to share the details I found for those who might have the same issue.
1st - Your `@Async`-annotated method should be declared in a separate bean rather than the `@Controller`- or `@RestController`-annotated bean.
2nd - You certainly need to declare the method `@Transactional` which is called from within `@Async` declared method. However, the very first method called from `@Async` method has to be defined `@Transactional`. I had the `@Transactional` method in second or third level in the method execution stack therefore the problem was not solved and I spent two days trying to figure out what was going on.
In normal circumstances (without `@Async`) a transaction gets propagated through the call hierarchy from one Spring component to the other.
When a `@Transactional` Spring `@Component` calls a method annotated with `@Async` this does not happen. The call to the asynchronous method is being scheduled and executed at a later time by a task executor and is thus handled as a 'fresh' call, i.e. without a transactional context. If the `@Async` method (or the component in which it is declared) is not `@Transactional` by itself Spring will not manage any needed transactions.
**Transactionl methods should be public.**
Since you have @Transactional on private method and also one called from the same class, there is no transaction and therefore detached state for save (see this). Not sure if you can apply @Transactional on run() or this class. Anyway, maybe you should create new "Service" class with public @Transactional method, and than call this service from your class.
https://stackoverflow.com/questions/25083295/spring-async-null-hibernate-session-on-lazy-collection
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