JDODetachedFieldAccessException: You have just attempted to access field "attachment" yet this field was not detached when you detached the object

Question

Entity class: ``` public class CustomerSurvey implements Serializable { @Id @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="CUSTOMER_SURVEY_SEQUENCE") @Column(name = "SURVEYID", nullable = false) private String surveyId; @Column(name="ATTACHMENT") @Lob private byte[] attachment; .... ``` Persistence class/logic: ``` public List getSurveysByCustomer(String custNo) throws WorkServiceException { EntityManager em = entityManagerFactory.createEntityManager(); Query query = em.createNamedQuery("customerSurvey.findByCustomer") .setParameter("custNo", custNo); logger.debug(query); List surveys = query.getResultList(); em.clear(); em.close(); return surveys; } ``` consumer class/logic: ``` List reviewSurveys = workService.getSurveysByCustomer("testCNo2"); for(CustomerSurvey rsurvey: reviewSurveys) { Object obj = rsurvey.getAttachment(); byte[] buffer = (byte[]) obj; OutputStream out = new FileOutputStream("C:\Temp\TulipsOut.jpg");…

Accepted Answer

The main problem is `private byte[] attachment;`.

- The default loading of `@Log` attribute will be `FetchType.LAZY`.

- The `Persistence Context` will be clear after the `clear()` process of `EntityManager`. That mean all of the managed entities will become detached state. More Information is here.

- When an `Entity` is detached state, if you access fetching value, you will get the problem as you mention.

Short Answer :

After `em.clear()` process, your entity instance `surveys` will be detached. That's why, you cannot retrieve the value `attachment` because of `attachment` is lazy loading(`FetchType.LAZY`).

Solution : use `FetchType.EAGER`. I think, most of the people don't recommend to use eager loading.

```
    @Column(name="ATTACHMENT")
    @Basic(fetch = FetchType.EAGER)
    @Lov
    private byte[] attachment;
```

JDODetachedFieldAccessException: You have just attempted to access field "attachment" yet this field was not detached when you detached the object

Solution

Problem