所以我有一个基本的 JSF 数据表,相关的部分是:
<h:dataTable value="#{actorTableBackingBean.allActors}" var="actor">
<h:column headerText="Actor Name" sortBy="#{actor.firstName}">
<h:outputText value="#{actor.firstName}" />
</h:column>
<h:column>
<h:form>
<h:commandButton value="Delete Actor"
action="#{actorTableBackingBean.deleteActor(actor)}"/>
</h:form>
</h:column>
<h:column>
<h:form>
<h:commandButton value="Randomize Actor Name"
action="#{actorTableBackingBean.editActor(actor)}"/>
</h:form>
</h:column>
</h:dataTable>
这就是 ActorTableBackingBean 的样子:
@Named
@RequestScoped
public class ActorTableBackingBean implements Serializable {
@Inject
ActorDao actorDao;
private List<Actor> allActors;
public List<Actor> getAllActors() {
return allActors;
}
@PostConstruct
public void fillUp(){
allActors = actorDao.getAllT();
}
public String deleteActor(Actor a){
removeActor(a);
return "/allActors.xhtml";
}
private String removeActor(Actor a){
try{
actorDao.deleteActor(a);
return null;
}catch (Exception e){
return null;
}
}
public String editActor(Actor actor){
actor.setFirstName("SomeRandonName");
actorDao.editActor(actor);
return "/allActors.xhtml";
}
}
最后是 ActorDao:
@Stateless
public class ActorDao extends GeneralDao<Actor> implements Serializable {
@Override
protected Class<Actor> getClassType() {
return Actor.class;
}
@Override
public Actor getWithId(int id){
TypedQuery<Actor> typedQuery =
em.createQuery("Select a From Actor a WHERE a.actorId =" + id,Actor.class);
return typedQuery.getSingleResult();
}
public void editActor(Actor a){
em.merge(a);
}
public void deleteActor(Actor a){
em.remove(a);
}
}
如您所见,edit Actor 调用了 em.merge(a)并且效果很好。但是em.remove(a)将返回:
Caused by: java.lang.IllegalArgumentException: Entity must be managed to call remove: com.tugay.sakkillaa.model.Actor@6ae667f, try merging the detached and try the remove again.
即使我尝试:
public void deleteActor(Actor a){
em.merge(a);
em.remove(a);
}
我仍然遇到同样的异常。
那么它如何用于编辑行,但不能用于删除它?
我能让它发挥作用的唯一方法是:
public void deleteActor(Actor a){
Actor actorToBeRemoved = getWithId(a.getActorId());
em.remove(actorToBeRemoved);
}
我做错了什么,或者无法理解?