We will be sending our instructors to take the EX300 Redhat exam soon and thought it would be good to record some of the labs we have them complete in our training labs. Whilst some of the lab are easy to generate like setting up Apache virtual servers, DNS, SAMBA etc the following test several areas of knowledge required for EX300.
I have been avoiding using Hibernate for a while now. I have been using alternatives such as the reference implementation, eclipselink or Apache's openjpa. But I have to keep up to date with Hibernate for our JBoss training sessions, where the more developer focused training sessions, often cover examples of hibernate with JBoss for EJBs.
In my previous post on JBoss password encryption I showed how to encrypt passwords for services that make use of the Jboss microcontainer. These services are configured in files that end with the suffix *-jboss-beans.xml. As stated in that post JBoss has a tendency for inconsistency in its configuration files and service setup due to its migration away from the JMX Kernel to the Microcontainer and its historical use of custom XML files for some setups like data sources.
JBoss 6 can make use of a centralised java keystore to save all the passwords needed in configuration files in a single place thereby making them easier to manage and protect. No more worrying about clear-text passwords in xml files! This feature is only available to services that make use of the microcontainer for service instantiation as it uses the microcontainer annotations.
When tuning a web site running on Apache for optimal performance there are two places to look. The first is picking the right combination of settings for the muli-processor module (MPM) you have selected and the second is tweaking the various settings that affect the caching and compression of web application content.
In October 2011 I gave a Tomcat Performance Tuning presentation at the Oracle South Africa User Group (SAOUG) conference hedl a Sun City. The confernce was attended by over 800 delegates and saw the addition of a Java track for the first time this year.
Its the end of the year again so I got some time to do complete a few projects, like build a media centre for the house. I got several TVs around the house and need a conveninet way to play movies on any TV in the house from a single source. The solution is to build a uPnP media source and then several media centres, 1 for each location.
When JPA 2 was released in 2009 it included the new criteria API. The purpose of the API was to get away from using JQL strings , (JPA Query Language), in your code. Although JQL seems like a great way to leverage your existing SQL knowledge ,in the OO world it has a major drawback namely; there is no compile time checking of your query strings. The first time you find out about a spelling or syntactical error in your query string is at run time. This can be quiet a productivity drain with developers having to correct, compile and redeploy to continue.
Usually this blog cover technical issues on Linux and Java and other kinds of geeky fun stuff but just this once I feel the need to say something about the political economy in South Africa, and how free and open source software could be used to help address the monumental challenges faced by our country.
When writing applications that need to track financial transactions most developers use BigDecimal to ensure that rounding is done properly and that there is no danger of arithmetic overflow or precision and scale being lost when performing arithmetic operations.
Using BigDecimal for tracking financial transactions is fine until you need to take into account other aspect of a financial transaction such as: