JPA:级联类型。PERSIST与多对一

我正在使用CascadeType。PERSIST与多对一

@ManyToOne(cascade=CascadeType.PERSIST)
@JoinColumn(name="Article")
private Article article;

持久性代码如下:

    Article article = new Article();
    article.setAuthor("Article Author");
    article.setTitle("Article Title");
    Comment comm1 = new Comment();
    comm1.setAuthor("Author1");
    comm1.setTitle("Title1");
    article.addComment(comm1);
    em.persist(comm1);
    em.getTransaction().commit();

我期望使用CascadeType。字段上的PERSIST将使持久化提供者按照这样的顺序对SQL进行排序,即先持久化父实体(本文中的文章),然后持久化子实体。但相反,我得到了

由:org.apache.openjpa.lib.jdbc引起。ReportingSQLException:无法添加或更新子行:外键约束失败

在这种情况下,正确的做法是什么?

文章:

@Entity
@NamedQuery(name="Article.findAll", query="SELECT a FROM Article a")
public class Article implements Serializable {
private static final long serialVersionUID = 1L;

@Id
private int id;

private String author;

private String title;

//bi-directional many-to-one association to Comment
@OneToMany(mappedBy="article",fetch=FetchType.LAZY,cascade=CascadeType.ALL)
private List<Comment> comments = new ArrayList<Comment>();

public List<Comment> getComments() {
    return this.comments;
}

public void setComments(List<Comment> comments) {
    this.comments = comments;
}

public Comment addComment(Comment comment) {
    getComments().add(comment);
    comment.setArticle(this);

    return comment;
}

........

注释:

@Entity
@NamedQuery(name="Comment.findAll", query="SELECT c FROM Comment c")
public class Comment implements Serializable {
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

private String author;

private String title;

//bi-directional many-to-one association to Article
@ManyToOne(cascade=CascadeType.PERSIST)
@JoinColumn(name="Article")
private Article article;

......

以下工作正常:

    em.getTransaction().begin();
    Article article = new Article();
    article.setAuthor("Article Author");
    article.setTitle("Article Title");
    em.persist(article);