Re: "Detached entity passed to persist"

Surprisingly, this (re-attaching a detached entity) is not a simple
problem. First of all, you need to be very careful about holding onto
entities in your session. It's too easy with JPA/Hibernate to accidentally
keep the whole query resultset in memory when you think you are holding
onto a single object (check with your jvisualvm). Second, since you are
using Hibernate, you can re-attach an entity with (the now deprecated
operation) session.lock(entity, LockMode.NONE), not absolutely sure how the
latest versions behave. I've written about it at
http://www.tynamo.org/tapestry-conversations+guide/, referencing this
stackoverflow issue about it:
https://stackoverflow.com/questions/912659/what-is-the-proper-way-to-re-attach-detached-objects-in-hibernate,
make sure you read all of it. Your best bet is to only store the company id
in the session and do a find() before setting the company (I know, it
defeats some of the perceived user benefits of using Hibernate/JPA).

Kalle


On Tue, Nov 28, 2017 at 7:55 PM, Christopher Dodunski <
[email protected]> wrote:

> Hi team,
>
> I suspect you'll be able to answer this right off the top of your head, as
> this error occurs in response to what I imagine is a very routine code
> assignment: set a newly created user's company to be the same company as
> that of the user doing the creating.
>
>
> Code snippet from 'pages/user/CreateUser.java'...
>
>     User user = new User(firstName, lastName, userName, email,
> authenticator.encryptPassword(password));
>
>     //Set the new user's company to the same as the creator's company
>     user.setCompany(authenticator.getLoggedUser().getCompany());
>
>     crudServiceDAO.create(user);
>
>
> The User>>Company relationship, as defined in the User entity class...
>
>     @ManyToOne(cascade=CascadeType.ALL)
>     @JoinColumn(name="COMPANY_ID")
>     private Company company;
>
>
> The Company>>User relationship, as defined in the Company entity class...
>
>     @OneToMany(mappedBy="company", cascade=CascadeType.ALL)
>     private Collection<User> users = new ArrayList<User>();
>
>
> The USER table has a COMPANY_ID field, so I'd be expecting Hibernate to
> create a new user with the same company ID as the user I have logged in
> as.  Instead, Tapestry gives the following error...
>
>     org.apache.tapestry5.runtime.ComponentEventException
>
>     detached entity passed to persist: com.example.harbour.entities.
> Company
>
>
> Why is this?  Appreciate your help.
>
> Thanks,
>
> Chris.
>
>
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