Hibernate JPA Caching

Question

I have a table named Master_Info_tbl. Its a lookup table: Here is the code for the table: ``` @Entity @Table(name="MASTER_INFO_T") public class CodeValue implements java.io.Serializable { private static final long serialVersionUID = -3732397626260983394L; private Integer objectid; private String codetype; private String code; private String shortdesc; private String longdesc; private Integer dptid; private Integer sequen; private Timestamp begindate; private Timestamp enddate; private String username; private Timestamp rowlastchange; //getter Setter methods ``` I have a service layer which calls the method service.findbycodeType("Code1"); same way this table is queried for the other code types as well e.g. code2, code3 and so on till code10 which gets the result set from the same table and is shown into the drop down of the jsp pages since these drop downs are in 90% of the pages I am thinking to cache them globally. Any idea how to achieve this? FYI: I am using JPA and Hibernate with…

Accepted Answer

(...) since these drop downs are in 90% of the pages I am thinking to cache them globally.

Using the query cache would be very appropriate for this use case. So activate the second-level cache, cache the `CodeValue` entity (see 2.2.8. Caching entities) and put the query behind `findbycodeType` in the query cache. To do so, use:

```
javax.persistence.Query query = manager.createQuery(...);
query.setHint("org.hibernate.cacheable", true);
```

And to clarify, the combination of the query and the values provided as parameters to that query is used as a key, and the value is the list of identifiers for that query. Schematically, something like that:

```
*--------------------------------------------------------------------------*
|                              Query Cache                                 |
|--------------------------------------------------------------------------|
| [ "from CodeValue c where c.codetype=?", ["Code1"] ] -> [ 1, 2, ... ]    |
| [ "from CodeValue c where c.codetype=?", ["Code2"] ] -> [ 3, 5, 6, ... ] |
*--------------------------------------------------------------------------*
```

So calling your method with different arguments won't "flush previous data", the argument is part of the key (or the query cache wouldn't work).

Note that this is Hibernate specific, JPA 1.0 doesn't specify second-level cache and query caching.

Hibernate JPA Caching

Solution

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