JPA独立实体已传递以保留

Question

I have a DAO with @Transactional annotation and with EntityManager inside.

Also I have a some IOC managed bean that has one transactional method inside.

And there are 2 entities with uni directional many2one -

@Entity
@Table(name = "AU_EVENT")
public class AuEvent { 
    @ManyToOne(fetch= FetchType.LAZY, cascade = {CascadeType.PERSIST, CascadeType.MERGE})
@JoinColumn(name = "MODULE_ID")
private AuModule auModule;
}

AuModule doesnt have reference on AuEvents

I'm trying to do like this

@Async
@Transactional(propagation = Propagation.REQUIRED)
public void onEvent(String moduleName, String instanceName){
        AuModule auModule = auModuleDao.findModule(moduleName, instanceName);
        if (auModule == null) {
            auModule = new AuModule();
            auModule.setInstance(instanceName);
            auModule.setName(moduleName);
        }
//doesnt help
//auModule = auModuleDao.getEntityManager().merge(auModule);

AuEvent auEvent = new AuEvent();
auEvent.setAuModule(auModule);
auEventDao.persist(auEvent); // error here [AuModule detached]
}

As I read in https://stackoverflow.com/questions/14057333/detached-entity-passed-to-persist-error-with-onetomany-relation I tried to do in this way

@Async
@Transactional(propagation = Propagation.REQUIRED)
public void onEvent(String moduleName, String instanceName){

    AuEvent auEvent = new AuEvent();
    auEventDao.persist(auEvent);

    AuModule auModule = auModuleDao.findModule(moduleName, instanceName);
    if (auModule == null) {
        auModule = new AuModule();
        auModule.setInstance(instanceName);
        auModule.setName(moduleName);
    }
    auEvent.setAuModule(auModule);
    auEventDao.persist(auEvent); // error here [AuEvent detached]
}

SO, does anyone know how I can avoid this? PS Please don't suggest me to write DAO method like that -

public void saveEvent(AuEvent auEvent, String moduleName, String instanceName){
    log.info("saveEvent({}) called...", auEvent);
    AuModule auModule = auModuleDao.findModule(moduleName, instanceName);
    if (auModule == null) {
        auModule = new AuModule();
        auModule.setInstance(instanceName);
        auModule.setName(moduleName);
    }
    auEvent.setAuModule(auModule);
    persist(auEvent);
}

I exactly want to save event&module not inside of any DAO

Thanks

Answer 1

In the second example, you should not call auEventDao.persist(auEvent); in the end. auEvent is already attached so its enough that your transaction just ends.
Also you shouldn't call persist() on object which is allready persistent. You should call it only on new objects. That's also the problem in your first example.

You call persist() only once on auEvent that's right. But sometimes there's existing (already persisted, found in DB) auModule associated with this auEvent . And you marked this association with CascadeType.PERSIST . So persist() is cascaded also to existing auModule -> exception thrown .

Something like this should work:
1.

@Async
@Transactional(propagation = Propagation.REQUIRED)
public void onEvent(String moduleName, String instanceName){
        AuModule auModule = auModuleDao.findModule(moduleName, instanceName);
        if (auModule == null) {
            auModule = new AuModule();
            auModule.setInstance(instanceName);
            auModule.setName(moduleName);
        }
       AuEvent auEvent = new AuEvent();
       auEventDao.persist(auEvent); 

       auEvent.setAuModule(auModule);
       auEventDao.merge(auEvent);
}

or
2.

@Async
@Transactional(propagation = Propagation.REQUIRED)
public void onEvent(String moduleName, String instanceName){

    AuEvent auEvent = new AuEvent();
    auEventDao.persist(auEvent);

    AuModule auModule = auModuleDao.findModule(moduleName, instanceName);
    if (auModule == null) {
        auModule = new AuModule();
        auModule.setInstance(instanceName);
        auModule.setName(moduleName);
    }
    auEvent.setAuModule(auModule);
    // optioanlly you can call here - auEventDao.merge(auEvent); 
}

Answer 2

In the onEvent() method you did not set the AuModule in the AuEvent after the if as you did in the saveEvent() method.

I hope this helps.