Dariusz on Software Quality

19/05/2010

Custom CacheProvider for Hibernate based on Websphere DistributedMap

Filed under: en — Tags: , , — dariusz.cieslak @

Hibernate is a library that maps database tables to Java objects. Is performance problems arise it’s very easy to add database caching for application using Hibernate (just few options in config file). Hibernate is shipped with EHCache, default cache implementation. It works well and is easy to setup.

Sometimes you have to use another caching library that has no direct support for Hibernate. Here the Hibernate API comes into play. I’ll show you how to plug Websphere’s DistributedMap into Hibernate.

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30/04/2010

How To Debug JNDI Lookup Problems

Filed under: en — Tags: , — dariusz.cieslak @

Sometimes when you get an exception like this:

javax.naming.NameNotFoundException: Name "comp/UserTransaction" not found in context "java:"

you want to see what entries are visible in JNDI. No problem, place this code somewhere near lookup problem code location:

InitialContext ic = new InitialContext();
NamingEnumeration it = ic.list("java:comp");
System.out.println("JNDI entries:");
while (it.hasMore()) {
    NameClassPair nc = it.next();
    System.out.println("JNDI entry: " + nc.getName());
}

You will see all JNDI names availailable on console then (you can use your logging library instead of course).

29/04/2010

Websphere Extreme Scale + Hibernate = ?

Filed under: en — Tags: , , — dariusz.cieslak @

Recently I was asked to integrate WXS (Websphere Extreme Scale, commercial cache implementation from IBM) into existing WPS (Websphere Process Server)-based project to implement read-only non-distributed cache (one independent cache instance per JVM). The idea is to plug cache implementation using 2nd level cache interfaces defined by Hibernate.

I plugged in the objectgrid.jar into hibernate configuration:

<property name="cache.provider_class">
com.ibm.websphere.objectgrid.hibernate.cache.ObjectGridHibernateCacheProvider
</property>

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22/04/2010

Recreate Derby Database Under WebSphere

Filed under: en — Tags: , , , — dariusz.cieslak @

WebSphere uses SQL databases for internal managment of MQ queues (Derby database engine under the covers). Sometimes you need to reset their state. Here’s the script that erase and recreate BPEDB database state (tested under WS 6.1.2):

rm -rf $WID_HOME/pf/wps/databases/BPEDB
echo "CONNECT 'jdbc:derby:$WID_HOME/pf/wps/databases/BPEDB;create=true' AS BPEDB;"|\
    $WID_HOME/runtimes/bi_v61/derby/bin/embedded/ij.sh /dev/stdin

14/04/2010

Second Level Cache For SQL Queries Under Hibernate

Filed under: en — Tags: , , , , , — dariusz.cieslak @

Second level cache in Hibernate allows to greatly speed-up your application by minimizing number of SQL queries issued and serving some results from in-memory cache (with optional disk storage or distributed cache). You have option to plug in different cache libraries (or to Bring Your Own Cache – an approach popular among my colleagues from India ;-) ). There are caching limits you must be aware of when implementing 2nd level cache.

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