The life cycle of entities are managed in persistence context.
We can detach and merge the instance of entities in persistence context.
There is no need to call a particular method to make your modifications persistent.
A straightforward wayt to update the state of an entity instance is to Sometimes this programming model is inefficient since it would require both an SQL SELECT (to load an object) and an SQL UPDATE (to persist its updated state) in the same session.
Recommendations: All these locks prevent dirty reads and non-repeatable reads on a given entity.
Optimistic locks enforce the lock as late as possible hoping nobody changes the data underneath while pessimistic locks enforce the lock right away and keep it till the transaction is committed.
The merge operation is clever enough to automatically detect whether the merging of the detached instance has to result in an insert or update. Hibernate provides more flush modes than the one described in the JPA specification.
In other words, you don't have to worry about passing a new instance (and not a detached instance) to During flush, an exception might happen (e.g. In particular It is quite cumbersome to save, delete, or reattach individual objects, especially if you deal with a graph of associated objects. Consider the following example: If the children in a parent/child relationship would be value typed (e.g.
The truly type-safe approach is the Criteria API explained in Chapter 9, Criteria Queries. While more verbose, it provides compiler-enforced safety (including down to property names) which will pay off when the application will move to maintenance mode.
Queries may specify a particular property of an entity in the select clause, instead of an entity alias. Returned non-transactional objects or aggregation results are considered "scalar" results and are not entities in persistent state (in other words, they are considered "read only"): Note that the actual program code is independent of the query language that is used, you may also define native SQL queries in metadata, or use Hibernate's native facilities by placing them in XML mapping files.
API allows you to change the state of an entity, or in other words, to load and store objects.