Data batch processing solution in Hibernate

Many people are skeptical about whether Java is suitable for batch data processing. As a result, it will be deemed that ORM may not be particularly suitable for batch data processing.
In fact, I think if we use it properly, we can eliminate the performance concerns of ORM in batch processing. The following uses Hibernate as an example to illustrate how to use Hibernate in Java to batch process data.
Insert 100 pieces of data into the database. Hibernate may be like this:
Session session = sessionFactory. openSession ();
Transaction tx = session. beginTransaction ();
For (int I = 0; I <100000; I ++ ){
Customer customer = new Customer (.....);
Session. save (customer );}
Tx. commit ();
Session. close ();
Memory overflow may occur when the number of logs reaches 50th. This is why Hibernate caches all recently inserted customers in the memory with session-level cache. Do not forget that Hiberante does not limit the cache size of the first-level cache:
# The Persistent Object instance is managed at the end of the transaction. At this time, Hibernate synchronizes with the database any managed objects that have been changed.
# Session implements asynchronous write-behind, which allows Hibernate to explicitly write a batch of operations.
Here, I will show how Hibernate implements batch insert:
First, we set a reasonable JDBC batch size, hibernate. jdbc. batch_size 20.
Then, flush () and clear () are performed on the Session at a certain interval ().
Session session = sessionFactory. openSession ();
Transaction tx = session. beginTransaction ();
For (int I = 0; I <100000; I ++ ){
Customer customer = new Customer (.....);
Session. save (customer );
If (I % 20 = 0 ){
// Flush insert data and release memory:
Session. flush (); session. clear ();}
}
Tx. commit ();
Session. close ();
So how to delete and update data? Well, in Hibernate2.1.6 or a later version, scroll () will be the best way:
Session session = sessionFactory. openSession ();
Transaction tx = session. beginTransaction ();
ScrollableResults MERS = session. getNamedQuery ("GetCustomers ")
. Scroll (ScrollMode. FORWARD_ONLY );
Int count = 0;
While (customers. next ()){
Customer customer = (Customer) MERS mers. get (0 );