:index-group: Unrevised
:jbake-type: page
:jbake-status: status=published
= Reload Persistence Unit Properties

This example aims to simulate a benchmark campaign on JPA.

First you’ll run your application then you’ll realize you need an L2
cache to conform to your Service Level Agreement (SLA).

So you change your persistence.xml configuration, then restart your
application, you wait a bit because you are using OpenEJB ;)…but you
wait…

So to try to go faster on long campaign simply change your configuration
at runtime to test it then when it works change your configuration file
to keep the modification.

To do it we can simply use JMX.

OpenEJB automatically registers one MBean by entitymanager (persistence
unit).

It allows you to change your persistence unit properties even if more is
possible.

== The test itself

The test is simple: we persist an entity, we query it three times
without cache then we activate cache and realize running again our
queries that one is enough to do the same.

== The output

In the ouput we find the 3 parts described just before.

[source,java]
----
INFO - TEST, data initialization
DEBUG - <t 1523828380, conn 93608538> executing stmnt 1615782385 CREATE TABLE Person (id BIGINT NOT NULL, name VARCHAR(255), PRIMARY KEY (id))
DEBUG - <t 1523828380, conn 93608538> [1 ms] spent
DEBUG - <t 1523828380, conn 1506565411> executing prepstmnt 668144844 INSERT INTO Person (id, name) VALUES (?, ?) [params=?, ?]
DEBUG - <t 1523828380, conn 1506565411> [0 ms] spent
INFO - TEST, end of data initialization


INFO - TEST, doing some queries without cache
DEBUG - <t 1523828380, conn 1506565411> executing prepstmnt 1093240870 SELECT t0.name FROM Person t0 WHERE t0.id = ? [params=?]
DEBUG - <t 1523828380, conn 1506565411> [0 ms] spent
DEBUG - <t 1523828380, conn 1506565411> executing prepstmnt 1983702821 SELECT t0.name FROM Person t0 WHERE t0.id = ? [params=?]
DEBUG - <t 1523828380, conn 1506565411> [0 ms] spent
DEBUG - <t 1523828380, conn 1506565411> executing prepstmnt 1178041898 SELECT t0.name FROM Person t0 WHERE t0.id = ? [params=?]
DEBUG - <t 1523828380, conn 1506565411> [1 ms] spent
INFO - TEST, queries without cache done


INFO - TEST, doing some queries with cache
DEBUG - <t 1523828380, conn 1506565411> executing prepstmnt 1532943889 SELECT t0.name FROM Person t0 WHERE t0.id = ? [params=?]
DEBUG - <t 1523828380, conn 1506565411> [0 ms] spent
INFO - TEST, queries with cache done
----
