使用ManyToMany的TomEE + OpenJPA不起作用 [英] TomEE + OpenJPA using ManyToMany does not work

问题描述

我正在撒谎。我不明白，它有多难？

I am throwing in the towel. I do not understand, how difficult can it be?

我有两个实体用户和群组，有多对多的关系。 组管理关系。所以在组我有：

I have two Entities User and Group, having a many to many relationship. Group manages the relationship. So in Group I have:

@Entity 
@Table(name = "GROUPS", catalog = "", schema = "GROUPADMIN")
public class Group {
  ...
  @ManyToMany
  @JoinTable(
    name = "GROUP_USERS",
    joinColumns = {@JoinColumn(name = "GROUP_ID")},
    inverseJoinColumns = {@JoinColumn(name = "USER_ID")}
  )
  private Set<User> users;

然后对于用户我创建实体的东西如下：

Then for User I create the entity something as follows:

@Entity 
@Table(name = "USERS", catalog = "", schema = "GROUPADMIN")
public class User {
  ...
  @ManyToMany(mappedBy="users")
  private Set<Group> groups;

然后在我的支持bean中，实际上是 @Named（注册表） ，我将对检索到的用户的引用存储为具有相同名称的属性。

Then in my backing bean, actually a @Named("registry"), I store a reference to a retrieved user as a property with the same name.

然后我在我的JSF中使用该支持bean

Then I use that backing bean royally in my JSF

Hello <h:outputLabel value="#{registry.user.firstName}"/>
<h:panelGroup>
  <h:dataTable value="#{registry.user.groups}" var="g">
    <f:facet name="header">Properties List</f:facet>
    <h:column>
      <f:facet name="header">Group</f:facet>
      <h:outputText value="#{g.id}"/>
    </h:column>
  </h:dataTable>
</h:panelGroup>

对于那些对表感兴趣的人：

For those interested in the tables:

create table "GROUPADMIN".GROUPS
(
  ID VARCHAR(15) not null primary key
);
create table "GROUPADMIN".USERS
(
  ID VARCHAR(50) not null primary key,
  PASSWORD VARCHAR(50),
  FIRST_NAME VARCHAR(50),
  LAST_NAME VARCHAR(50)
);
create table "GROUPADMIN".GROUP_USERS
(
  GROUP_ID VARCHAR(15) not null,
  USER_ID VARCHAR(50) not null,
  primary key (GROUP_ID, USER_ID)
);

首先注意到的是，组似乎是空的，不是空的，而是空的（通过调试等验证） ）。所以我明白默认情况下 @ManyToMany 会使用Lazy绑定，所以我将其更改为 fetch = FetchType.EAGER （并不是说这应该重要）。在这样做之后，事情变得奇怪......

First thing noticed is that groups appears to be empty, not null, but empty (verified with debugging etc). So I understood that by default a @ManyToMany would use Lazy binding, so I changed this to fetch = FetchType.EAGER (not that this should even matter). After doing so, things really got bizarre ...

此时EL开始抱怨上的id属性＃{ g.id}：

Caused by:
javax.el.PropertyNotFoundException - Property 'id' not found on type org.apache.openjpa.util.java$util$HashSet$proxy
at javax.el.BeanELResolver$BeanProperties.get(BeanELResolver.java:266)

为什么要检索属性 id 在 HashSet 代理上，而不是组？

Why is it trying to retrieve property id on a HashSet proxy, and not on a Group?

所以我很好奇我实际上从< h：dataTable> g 属性>，我试图输出它只需使用< h：outputText value =＃{g}/> ...结果非常有趣...

So me being curious what I actually got into that g attribute I got from the <h:dataTable>, I tried to output it simply using <h:outputText value="#{g}"/> ... result was really interesting ...

打印出的 g 不仅仅是 Set< Group>中的一个元素，但实际上是coll ection本身，它与之前显示的异常相匹配......这更能说明API或集成中的错误？

What g printed out was not just one element out of the Set<Group>, but was actually the collection itself, which matches the earlier shown exception ... that's more indicative for a bug in the API or integration?

所以基本上它看起来有些东西被打破了，虽然我怀疑这一切都与同一个问题有关。

So basically it looks like several things are broken, although I suspect it all relates to one an the same issue.

请注意，我使用的是基本的现成TomEE，最新版本，没有自定义（JPA没有增强器）另外）。

Note that I used a basic off-the-shelf TomEE, latest version, no customization (no enhancer for JPA also).

推荐答案

为什么它应该有效： JSR 338：JavaTM持久性2.1。

错误提交： Jira Issue OpenJPA-2546 （请对此问题进行投票决定。）

Bug submitted: Jira Issue OpenJPA-2546 (please vote on getting this resolved).

解决方法：使用列表< T> 替换设置< T> 作为解决方法。

Workaround: replace Set<T> with List<T> as a workaround.

这篇关于使用ManyToMany的TomEE + OpenJPA不起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！