休眠查询未在同一事务中找到“待定”实体

Question

I've got an app for importing data into a ManyToMany structure.

    @Table(name="content")
    class Content {
      @Column(.., unqiue=true)
      String str;
    }

    @Table(name="group")
    class Group {
      @JoinTable("group_content"..)
      List<Content> contentList;
    } 

The Content has a unique column str (as seen above) which is used by the app to identify the content already exist in database - and if so re-use that entity rather than adding it again.

This is done with a findByStr(String str) method in a ContentDao implementation. It's implemented as a NamedQuery ( from Content c where c.str = :str ).

When I run an import where both groups and content is new and the some groups refeer to the same (new) content it does seem that my findByStr query returns NULL .

The query works fine outside of this scenario but it seems when Content objects has been created, but not committed, the query does not detect them.

Currently to work around this I'm actually keeping a Map<String, Content> to double check against if the query returns NULL .

Answer 1

Hibernate do not execute all insert statements immidiately. Make sure that before each call to findByStr all SQL inserts for all new objects are sent to DB. You can ensure it by doing:

• Tell to Hibernate to take into account all new objects. For example you can do it by executing session.save(group) for each new group object (which will take into account related content objects)
• execute one time session.flush()

Normally after these all changes must be available for your query in the same transaction.