Question

Hi in my application i have few small tables and i cache them All at the server startup in a Map. I want to implement same functionality by Ecache + hibernate combination

my class looks like

  @Entity
  @Table(name = "Order")
  @NamedQueries
  ({
     @NamedQuery(name="Order.findBySource", 
        query="from Order a where a.source = :source"),

     @NamedQuery(name="Order.findByAll", 
        query="from Order"),

     @NamedQuery(name="Order.findByPrioritySource", 
        query="from Order a where a.priority = :priority and a.source =   :source"),

     @NamedQuery(name="Order.findByPriority", 
        query="from Order a where a.priority = :priority"),

     @NamedQuery(name="Order.findByWhenModified", 
        query="from Order a where a.whenModified = :whenModified")
     })
      @Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)

    public class Order implements java.io.Serializable {

      private String source;
      private long priority;
      private Date whenModified;
    }

this order table has hardly 10 entries and i want to keep this table in memory all the time.
any insights how can i achieve this?

i fire the above named queries to fetch the orders. I do not want to go to DB again and again when i fire this query so for this in ecache.xml do i need to make an entry of this class ? or i need to cache these Named queries in ecache.xml?

is it possible to replicate the Map implementaion by Ehcache. so that i can get the object just by specifying the ID from the cache without hitting the DB again and again ?

Answer 1

The thing you need is Hibernate query cache. First of all you need to enable it on Hibernate level by setting hibernate.cache.use_query_cache property to true. Then when you execute your query in the code you need to set a flag on the query object to indicate that it requires caching:

Query q = session.getNamedQuery("Order.findByPriority");
q.setCacheable(true);
List result = q.list();