JPA将ID设置为零后保留实体

Question

I have the following three entities

@Entity
class Session {

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval=true)
     @JoinColumn(name="session_id", referencedColumnName="id")
    private List<Testcase> testcases;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval=true)
    @JoinColumn(name="session_id", referencedColumnName="id")
    private List<SessionChart> sessionCharts;
}

@Entity
class SessionChart {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval=true)
    @JoinColumn(name="sessionChart_id", referencedColumnName="id")
    private List<ChartMeasurement> chartMeasurement;

}


@Entity
class ChartMeasurement {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    @ManyToOne
    @JoinColumn(name = "testcase_id", nullable=true, referencedColumnName = "id")
    private Testcase testcase;
}

and its corresponding getters and setters. Creating a new session and persisting it with out any session charts and chart measurements works great. But I have a save as functionality when I can open a previous saved session from a different user and rename it (change the owner as me) and resave it thus creating a new database record. I do this by setting id 0 to the entity and all its sub entities, that is Testcases list sessionCharts list and all chartMeasurement entitites inside sessionCharts list. But when trying to persist I get the following error

object references an unsaved transient instance - save the transient instance before flushing : ChartMeasurement.testcase -> Testcase

How can I overcome this behavior?

Answer 1

I'm going to assume you are using JPA and thus are using an javax.persistence.EntityManager instance.

I would suggest detaching the object before changing the ID's and performing a persist.

For example,

entityManager.detach(instanceOfYourObjectHere);

What's happening is that the Session is holding a reference to your object instance and is confused as you have changed the primary keys.