我在尝试进行ManyToMany级联事件时遇到了麻烦.我已经浏览了类似的文章,但是与其他文章相比,我的代码哪里出错了.

我有两个表Organization和Project,Organization是关系的所有者,并且两者之间有一个关系表.

我试图保留一个新的项目实体,该实体可以具有一个或多个与其关联的组织.我使用selectManyListbox(JSF 2)让用户选择多个组织.在我尝试级联关系之前,所有这些工作都很好.对于与项目关联的每个组织,要么只是持久化项目,要么是持久化经理创建同一项目的新副本.即不同的orgID和projID(而不是不同的orgID引用相同的projID)

当我尝试保持关系时,为什么JPA会创建同一Project的新实例(相同的属性,除了ID)？

我正在尝试学习JPA / JSF,非常感谢您的帮助.问候克里斯.

PS.在Project bean控制器中,我获得了用户选择的正确的Organization实例.

具有主键的实体对象

public class Organisation implements Serializable {

private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "idOrganisation")
private Integer idOrganisation;

..

@JoinTable(name = "organisationproject", joinColumns = {
        @JoinColumn(name = "fkOrganisation", referencedColumnName = "idOrganisation")}, inverseJoinColumns = {
        @JoinColumn(name = "fkProject", referencedColumnName = "idProject")})
@ManyToMany (fetch=FetchType.EAGER, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH})
private Collection<Project> projectCollection;

..
}

public class Project implements Serializable {

private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "idProject")
private Integer idProject;

..

@ManyToMany(mappedBy = "projectCollection")
    private Collection<Organisation> organisationCollection;
..
}

项目bean控制器

@ManagedBean (name="projectController")
@SessionScoped
public class ProjectController implements Serializable {

private Project current;
private UISelectMany selectedOrganisations;

...

public String create() {
        UserController userBean = JsfUtil.findBean("userController", UserController.class);
        current.setUser(userBean.getSessionUser());
        current.setTimeStamp(JsfUtil.getTimeStamp());
        try {


            //Use the OrganisationFacade, who is the owner of the relationship and uses Cascade to update the relation
            for(Organisation org : current.getOrganisationCollection()) {
                org.getProjectCollection().add(current);
                ejbOrganisationFacade.edit(org);

            }

            //getFacade().create(current);

            JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/resources/Bundle").getString("ProjectCreated"));
            return prepareCreate();
        } catch (Exception e) {
            JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/resources/Bundle").getString("PersistenceErrorOccured"));
            return null;
        }
    }

public UISelectMany getSelectedOrganisations() {
        return selectedOrganisations;
    }

public void setSelectedOrganisations(UISelectMany selectedOrganisations) {
        this.selectedOrganisations = selectedOrganisations;
    }
...
}

最后是Organiasation立面编辑功能

@Override
    public void edit(Organisation entity) {
        getEntityManager().merge(entity);
    }

解决方法:

解决了问题,然后将重播发布给可能会犯与我相同的错误的其他人.希望没事.

问题出在Project bean的create函数中.在合并(更新)组织实体之前,我必须先在项目上调用创建(持久).

try {

            getFacade().create(current);

            for(Organisation org : current.getOrganisationCollection()) {
                org.getProjectCollection().add(current);
                ejbOrganisationFacade.edit(org);
            }

            JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/resources/Bundle").getString("ProjectCreated"));
            return prepareCreate();
        } catch (Exception e) {

另外,我在项目外观的create方法中出错,该方法称为merge而不是persist.这会导致很多问题.很抱歉占用如此微不足道的解决方案的空间.