无法使用 grails 和 JPA 将集合中新添加的项目更新到数据库

Question

我在长期更新 grails 中的一个域（图书馆）时遇到问题，我尝试在添加新书后更新我的图书馆，但添加的书没有得到保存。

I have mapping of bookCollection in my domain Class Library as below:

@OneToMany(cascade = CascadeType.ALL, mappedBy = "Library")
    Collection<Book> bookCollection;


I am trying to add a new book to my Library(Initially there is no book in  bookColletion):

Library library = Library.get(1)
Book book=Book.get(1)
library.bookCollection.add(book)

and update it:
library.save(flush:true,failOnError: true)

Library is got saved but  my book is not.

I am using grails and JPA.

谢谢

Answer 1

您没有设置关系的另一端：library 的 book。

Library library = Library.get(1)
Book book=Book.get(1)
library.bookCollection.add(book)
book.library = library; // <--- sets the other side of the relation