My expectation is that a lazy loaded collection should be fetched when the collection is accessed within a transactional scope. For example, if I want to fetch a collection I can call foo.getBars.size(). The absence of an active transaction should result in an exception with an error message like
failed to lazily initialize a collection of bars: .... could not initialize proxy - no Session
However, I noticed that the behavior is different in my latest application. I'm using Spring Boot 1.5.1 with the "data-jpa" starter. I have used Spring Boot in the past, but the data-jpa starter is new for me.
Consider the following case. I have a lazy loaded ManyToMany collection.
@SuppressWarnings("serial")
@Entity
@Table(name = "foo")
public class Foo implements java.io.Serializable {
....
private Set<Bar> bars = new HashSet<Bar>(0);
....
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinTable(name = "foo_bar_map",
joinColumns = {@JoinColumn(name = "foo_id", nullable = false, updatable = false)},
inverseJoinColumns = {@JoinColumn(name = "bar_id", nullable = false, updatable = false)})
public Set<Bar> getBars() {
return this.bars;
}
public void setBar(Set<Bar> bars) {
this.bars = bars;
}
My service method is NOT marked as Transactional but I am accessing a lazy loaded collection
@Service
public class FooServiceImpl implements FooService {
@Autowired
private FooRepository fooRepo;
@Override
public FooDTO findById(int fooId) {
Foo foo = fooRepo.findOne(fooId);
// The FooDTO constructor will access foo.getBars()
return new FooDTO(foo);
}
And for context on the FooDTO constructor
public FooDTO(Foo foo) {
...
for (Bar bar : foo.getBars()) {
this.bars.add(bar);
}
}
Contrary to my expectation and past experience, this code executes successfully and fetches the collection. Further, if I throw a breakpoint in my service method, I can step through the code and see the SQL statements in my logs that fetch the bars after my call to the fooRepo. After my call to fooRepo, I expect the transaction to be closed.
What's happening here?
