Question

我尝试使用JPA在一对多关系中创建新记录。我一直得到一个＆＃39; javax.ejb.EJBException：Transaction aborted＆＃39;例外。经过调试，我发现我正在使用的作者对象没有返回主键，因此无法设置＆＃39; AuthorID＆＃39;在它的＆＃39;各自的书籍收藏对象。

我试过这个

author = new Author();
book = new Book();
Collection<Book> list = new ArrayList<>();

author.setAuthorFirstName(request.getParameter("authorFirstName"));
author.setAuthorLastName(request.getParameter("authorLastName"))
authorService.create(author);
//authorService.flush();

book.setTitle(title);
book.setDatePublished(sdf.parse(userEnteredDate));
book.setAuthorID(author);
list.add(book);
author.setBookCollection(list);

authorService.edit(author);

我也试过这个：

author = new Author();
book = new Book();
Collection<Book> list = new ArrayList<>();   

author.setAuthorFirstName(request.getParameter("authorFirstName"));
author.setAuthorLastName(request.getParameter("authorLastName"));
authorService.create(author);
authorService.flush();
Author author2 = authorService.edit(author);
book.setTitle(title);
book.setDatePublished(sdf.parse(userEnteredDate));
book.setAuthorID(author2);
list.add(book);
author2.setBookCollection(list);
authorService.edit(author2);

门面：

 public abstract class AbstractFacade<T> {
 private Class<T> entityClass;

 public AbstractFacade(Class<T> entityClass) {
    this.entityClass = entityClass;
 }

protected abstract EntityManager getEntityManager();

public void create(T entity) {
    getEntityManager().persist(entity);
}

public T edit(T entity) {
    return getEntityManager().merge(entity);
}

public void remove(T entity) {
    getEntityManager().remove(getEntityManager().merge(entity));
}

public T find(Object id) {
    return getEntityManager().find(entityClass, id);
}

public List<T> findAll() {
    javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
    cq.select(cq.from(entityClass));
    return getEntityManager().createQuery(cq).getResultList();
}

public List<T> findRange(int[] range) {
    javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
    cq.select(cq.from(entityClass));
    javax.persistence.Query q = getEntityManager().createQuery(cq);
    q.setMaxResults(range[1] - range[0] + 1);
    q.setFirstResult(range[0]);
    return q.getResultList();
}

public int count() {
    javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
    javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
    cq.select(getEntityManager().getCriteriaBuilder().count(rt));
    javax.persistence.Query q = getEntityManager().createQuery(cq);
    return ((Long) q.getSingleResult()).intValue();
}

public void flush(){
    getEntityManager().flush();
}

public void refresh(T entity) {
    getEntityManager().refresh(entity);
}

}

我已经阅读了本网站和其他几个网站上发布的所有其他类似问题，但这些技术似乎都没有奏效。有人可以解释为什么没有检索到AuthorID吗？

JPA一对多PK返回空（持续）

0 个答案: