如何在休眠状态下不向表1和表2添加数据而向表3创建数据和向表3添加数据

Question

I am new to Hibernate and not able to find out a way of the situation that I have. It is kind of Many to Many relationship but the only difference is that I want the data to be only inserted in table 3 and not in table 1 & table 2.

Table 1 and Table 2 already has all the data present.

Current Requirement:

Table 1 has user id, first name, last name (Already Exists) Table 2 has document id, document name, document content (Already Exists) Table 3 should have user id and document id Both Table 1 & Table 2 already has all the data prepopulated. Now if a user views a document, I want to make an entry in the third table without persisting or updating in Table 1 & Table 2. We want to maintain data on the documents which are viewed by a user so that even when the user logged off and login back we can show him only the docs which are unread. What is the best use of Hibernate in this situation?

Answer 1

You don't need to update the people nor the document table. Hibernate is able to add entries to your third table (the join table) if you configure everything right. You just annotate a collection with @ManyToMany and make sure you are working with entities from the DB instead of creating new ones:

• load person from DB
• load document from DB
• put document into the list of the person
• save person entity

See here: http://www.mkyong.com/hibernate/hibernate-many-to-many-relationship-example-annotation/ for a good walkthrough