Lists we get from query.getResultList() are of course immutable.
But if I have an entity which has a @ElementCollection or a @OneToMany List<OtherEntity> then those imo should be mutable. Regardless whether in attached or detached state.. It is obvious for @ElementCollections but also for e.g. @OneToMany with CascadeType.ALL. Otherwise entityManager.merge() would not make much sense imo... I was always under the impression that this works perfectly fine, even in detached state. We do not exchange the lists in those entities when we perform a detachment afaik. We only change the StateManager to a DetachedStateManager, but thats's it basically. LieGrue, strub >________________________________ > From: Rick Curtis <curti...@gmail.com> >To: users <users@openjpa.apache.org> >Sent: Tuesday, 22 October 2013, 18:30 >Subject: Re: Immutable list in entity > > >I don't have a solid answer, but have found a number of posts throughout >the years on markmail[1]. I'm just heading out to lunch, but I'll read >through those sometime later today. > >[1] http://openjpa.markmail.org/search/?q=%22Result+lists+are+read+only%22 > > > >On Tue, Oct 22, 2013 at 11:05 AM, José Luis Cetina <maxtorz...@gmail.com>wrote: > >> Sorry about String immutable, let my explain me. >> >> (The entities is just an example for demostrate this) >> >> @Entity >> private MyClass implements Serializable{ >> >> private String name="old value"; >> @ManyToOne >> private List<Product> products; >> // getters and setters.. >> } >> >> Example 1 >> 1. Get MyClass entity in a managedbean from and ejb (ejb use a query and >> the products attribute is null because is LAZY LOADING). >> 2. inside of the managedbean try to set a new value for name >> myClass.setName("new value); //the value is refreshed from "old value" to >> the new value "new value" >> 3. inside of the managedbean try to set a new list of products like: >> List<Product> myNewList = new ArrayList<Product>(new Product()); >> //then try to set this new list to the entity, remeber that we are in >> the managedbean and the entity is detached >> myClass.setProducts(myNewList); // here i set the new list but no >> matter what list of product i set to my entity the list of product remains >> null, like if the list is like readonly >> myClass.getProducts().size();//i get a nullpointer here >> >> Example 2 >> 1. Get MyClass entity in a managedbean from and ejb (ejb use a query and >> the products attribute contains N elements (IS NOT EMPTY OR NULL) because >> is EAGER LOADING). >> 2. inside of the managedbean try to set a new value for name >> myClass.setName("new value); //the value is refreshed from "old value" to >> the new value "new value" >> 3. inside of the managedbean try to clear the list of the entity you get an >> exception >> myClass.getProducts().clear(); // here i get an exception "Result lists >> are read only" >> >> >> I cannot find anywhere in the specification like "results lists have to be >> readonly and other values not". >> >> This is why i asked "the list values have to be immutables in an entity >> even when the entity is detached?" >> >> >> Then i ask again, why list are read only and any other value not? >> >> >> >> >> 2013/10/22 Albert Lee <allee8...@gmail.com> >> >> > String type is immutable, meaning if you are holding on a reference to >> it, >> > it will never be changed even it is "modified" since a new >> object/reference >> > will be created. >> > >> > List type is not immutable, regardless of if it is used in an JPA Entity, >> > either managed or detached. >> > >> > Not sure exactly what you are looking for but an example may be helpful >> > here. >> > >> > >> > >> > On Tue, Oct 22, 2013 at 9:27 AM, José Luis Cetina <maxtorz...@gmail.com >> > >wrote: >> > >> > > Hi, i want to know if the default openjpa behavior about list >> attributes >> > in >> > > an entity >> > > >> > > When i retrieve and entity (that has list values) and detached it from >> em >> > > and then return (from ejb) to my web tier (jsf app), the list values >> are >> > > immutable but other object are mutables like strings, I cannot find in >> > the >> > > specification if this is the expected behavior, the list values have to >> > be >> > > immutables in an entity even when the entity is detached? >> > > >> > > Thanks >> > > >> > >> > >> > >> > -- >> > Albert Lee. >> > >> >> >> >> -- >> ------------------------------------------------------------------- >> *SCJA. José Luis Cetina* >> ------------------------------------------------------------------- >> > > > >-- >*Rick Curtis* > >
