Web proxy server - CHAPTER 12 Modifying objects efficiently A Hibernate extension
CHAPTER 12 Modifying objects efficiently A Hibernate extension cascading option can be used either as an addition to the options already set on the association annotation (first and last example) or as a stand-alone setting if no standardized option applies (second example). Hibernate s association-level cascade style model is both richer and less safe than persistence by reachability. Hibernate doesn t make the same strong guarantees of referential integrity that persistence by reachability provides. Instead, Hibernate partially delegates referential integrity concerns to the foreign key constraints of the underlying SQL database. There is a good reason for this design decision: It allows Hibernate applications to use detached objects efficiently, because you can control reattachment and merging of a detached object graph at the association level. But cascading options aren t available only to avoid unnecessary reattachment or merging: They re useful whenever you need to handle more than one object at a time. Let s elaborate on the transitive state concept with some example association mappings. We recommend that you read the next section in one turn, because each example builds on the previous one. 12.1.3 Working with transitive state CaveatEmptor administrators are able to create new catego ries, rename categories, and move subcategories around in the category hierarchy. This structure can be seen in figure 12.2. Now, you map this class and the association, using XML:
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