Since version 9, Java has new features every 6 months and it’s very hard to keep track of these new changes. Most of the information on the internet describes changes between the last 2 Java versions. However, if you’re in a similar situation as me, you’re not using the last Java version but a version several releases older.(more…)
A singleton pattern is probably the simplest well-known design pattern, but still people often implement it incorrectly in Java. (more…)
Java EE 7 is around for a few years already, and provides several very useful and long-awaited features, like entity graphs and better support for stored procedures and results mapping. For an overview, have a look at Thorben Janssen’s blog post. The query capabilities were also enhanced, with 3 additional keywords. All of them are available in both JPQL and Criteria API:
- ON keyword to specify conditions for JOINs
- FUNCTION to call arbitrary database function
- TREAT to downcast entities to their specific type
In this post, I’ll focus on the first of them – the ON keyword in JOINs. (more…)
This post summarizes what needs to be done in order to use Facelets instead of default JSP as a view technology for MVC framework.
Although MVC is a fresh new framework, the default view technology used in most examples – JSP – is rather old and sometimes cumbersome. On the other hand, the older brother JSF already builds on more modern and flexible Facelets.
Fortunately, MVC framework has been designed to support many alternative view technologies out of the box, including Facelets. (more…)
JPA provides essentially 2 types of locking mechanisms to help synchronize access to entities. Both mechanisms prevent a scenario, where 2 transactions overwrite data of each other without knowing it.
By entity locking, we typically want to prevent following scenario with 2 parallel transactions:
- Adam’s transaction reads data X
- Barbara’s transaction reads data X
- Adam’s transaction modifies data X, and changes it to XA
- Adam’s transaction writes data XA
- Barbara’s transaction modifies data X and changes it to XB
- Barbara’s transaction writes data XB
As a result, changes done by Adam are completely gone and overwritten by Barbara without her even noticing. A scenario like this is sometimes called dirty-read. Obviously, a desired result is that Adam writes XA, and Barbara is forced to review XA changes before writing XB.
How Optimistic Locking works
Anybody I don’t like, read this! :
com.superframework.core.base.Object object = new com.superframework.core.base.Object()
Sometimes one cannot avoid this rubbish in Java, even today. I do not wish my enemies to read such code, not in my code I want to be proud of!
I wonder how many times I have asked myself why Java is so complicated to read and write? Why I have to keep writing so many characters and lines of code to express a simple repetitive task? It’s appeared to me like Java language designers keep torturing developers by forcing us to use constructs invented 15+ years ago without an alternative.
But this one is simply an outrage. (more…)
Ever wondered why Eclipse/Netbeans keeps pausing for a while every now an then? Especially right at the time when you want to show something in the code to your dear colleages? It feelt embarrassing and awkward, didn’t it?
I found out that most of the time the IDE pauses because of Garbage Collector execution. The subtle little element in design of JVM, which usually does great job in relieving us developers from worrying about memory consumption, and most people are just happy that it does its job well and ignore it most of the time. However, the consequences of running Garbage Collector may surprise us if we simply ignore it. (more…)
After having the pleasure of building my code around CDI for couple of years, it feels very natural to use it to structure my code according to well-known patterns. CDI is a dependency injection mechanism designed to be used within Java EE application servers, and this could be perceived as a disadvantage. However, I want to show that it can be used and has great potential also in a Java SE application.
What is great about CDI is that it is much more than an injection mechanism. On top of this it provides also an elegant and powerful event passing mechanism. This feature can be nicely combined with Swing to build a GUI application based on MVC pattern.
It is really possible to efficiently combine CDI and Swing framework to build a Java GUI application rapidly and with a clear structure.