How query level cache works in Hibernate.

 To   understand  the query level cache   we  will    a   sample  code    which  is    written  for  

  for  employee table   using  query level cache . 

   

session = factory.openSession();

company1=(Company)session.get(Company.class, 1);

session.close();

//second block

session = factory.openSession();

tx = session.beginTransaction();

Query updateQuery=session.createQuery("update Company set companyName = 'newCompany' where companyId=1");

updateQuery.setCacheable(true);

updateQuery.executeUpdate();

tx.commit();

session.close();

//Third block

session = factory.openSession();

company1=(Company)session.get(Company.class, 1); // line 1

session.close();

  The  question  is  how    we  will   get  update  data  at  third  block of the  code.

 here  is what  happens   when you use query   level cache .

The query cache stores IDs returned by previous executions of a cacheable select query.

Let's say you execute the following cacheable query:

select line from OrderLine line join line.order order

where line.status = ? and order.date = ?

If you execute it once, Hibernate will store the IDs of the lines returned by the query in its query cache. And it will store the lines themselves in the second-level cache.

If you execute the same query a second time, with the same parameters, Hibernate will extract the IDs from the query cache, without executing the select query. Then it will get every line by ID (which should be fast since the lines are in the second-level cache

If you insert, update or delete a line or an order, Hibernate will detect it. Since this modification could affect the result of the cached query, the cache entries associated with this query in the query cache will be evicted. So the nexttime you execute this query again, it will be executed against the database, and the results will be stored again in the query cache