In a project that I mention a lot there's an persistent model using JPA as an interface to Hibernate.

There was case where I wanted to put extra columns in a @ManyToMany relationship. JPA cannot do that.

So I had to use the Hibernate's @CollectionOfElements.
It works like that: if there are the objects Class and Student, the extra columns go to the wrapper class EnhancedStudent. The EnhancedStudent has a property of type Student.

Now I have a few bugs related to it:

1. Causes the @Version of the containing object (Class) to increment on EntityManager.html#find(java.lang.Class, java.lang.Object)
2. The creation of an ExtraStudent cannot propagate (cascade) the inner Student - no matter what.

The funniest thing is that the documentation of the @CollectionOfElements is a single line:


http://www.hibernate.org/hib_docs/annotations/api/org/hibernate/annotations/CollectionOfElements.html

:(

From some time I noticed that Mtel (my mobile service operation) is using VoIP when I'm calling an Mtel number while roaming.
When I'm calling another operator's number while still roaming, there's no VoIP.

CHEAP BASTARDS. For these prices you can at least provide a decent service - a VoIP call is with bad quality and the callee cannot see who's calling, he sees some service number.

BUT THATS NOT ALL.

The top of the cherry is that when Mtel is using VoIP they clearly cannot see whether the other side answers or not, so no matter whether you make a successful call or not - while you're ringing you get billed. That's not right, is it?!

I found out all that today while checking my bill. Two months ago while in Brno I made a call and was quite sure that I would get billed for that call even though nobody answered.

GOTCHA, YOU CHEAP BASTARDOs


Update: other case of proved cheating:
Mtel made me pay 200 bucks for half a megabyte of internet while roaming. Before that I explicitly asked for the price. It came out that the price is 10 times more and they charge every GPRS session for a full megabyte (with 10 times the prices) without saying it.

Few months ago I caught them billing me for an international call to a friend I haven't spoken with for at least a couple of years.

Ctrl+Shift+T is a popular shortcut in Eclipse.

Ctrl+T is a popular shortcut in Firefox - opens an empty tab.

Once by mistake I pressed the former by mistake and found out that Ctrl+Shift+T makes an undo for the last closed window (tab). And not only for the last tab.

Cool

There are a lot of tests for some EJBs.

Starting an J2EE server is slow. I wanted to test the business logic faster.

Most of the beans reference only each other and a persistence context.

So what should the mock worry about - transaction demarcation and dependency injection. And... exception wrapping and unwrapping.

1. First just add some setters or change the access level modifiers (from private to protected for example).
2. Know your transaction authority.
   
3. Count started transactions. If 0, begin. If 0, commit. Rollback when necessary.
   
4. Listen for all the exceptions and wrap and unwrap them.
5. Reuse as much as possible of the code.
   

If I have some spare time left, I'll write some code.

I'll try to simplify it.
There's an object model. In it there are cyclic references (one object references a second one, the second one - a third one, the third one - the first one).
Some of the cyclic references are through aggregations - one object has a map of other objects.
Some of the objects have a meaningful hashCode() and equals() overridden. These two depend on some properties in the object itself.

Some of the objects get serizalized/deserialized (travel through a stream).

Now here comes the problem - the deserialization first sees the cyclic reference, makes instances of all the objects, initializes all the primitive fileds, does not initialize the other fields, then links the objects.

Here comes the problem, linking two objects (one of which has a map of the other) requires hashCode(). This requires some specific properties in that object that are not initialized - this causes NullPointerException (or in my case an AssertionError).

If the hashCode returns a default value if the properties are not there - another serious problem si caused - there are objects in the map in the wrong buckets - they entered the map with the default hash, but when they got completely initialized - they now have a different hash. I think that is really bad - the map has to be rehashed.

Here's a bug detail:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4957674

Here's what some of the guys say on the subject:


And:


But, not all my object have a rewritten equals (of course I can check with reflection which ones do and which ones don't, but...). This would also mean that I'm using a customized collection.


There's another proposition - to hash the hashcode.


The hashcode is a primitive type, so it would get initialized first and the problem would be solved. This would mean to have an hashCode() and equals() which check which one is available - the cached hash or the properties - isn't that UGLY.

I'll investigate more.

This is 73 meters from the ground. It is scary and physically intensive. I did this route twice, the first time without the special gloves. My fingers still hurt.



On the top the second time (on the verge of not making it).


It's over, let's have something to eat.


More pictures when I get them.

The first idea was to have the DB (MySQL) start as part of the script that launched the tests. Google couldn't find anything good. MySQL is one of the most unintuitive things I have ever seen, so the decision was to not try to figure it out on my own.

The next thing was to install MySQL as a service. That turned out to be difficult.

I tried to install MySQL as a service:


As easy as that. The problem is IT DID NOT WORK. The service did not want to start.

After some reading it came out that the RIGHT way was to do it like that:


Why do I have to supply the mysql directory explicitly?
Why do I have to supply the my.ini directory explicitly?

Why doesn't mysqld give me an error message when I install it without the needed parameters?
Why doesn't mysqld give me an error message when I install it without the needed explicit paths?

...is beyond my inderstanding.

MySQL, you are a disgrace.
MySQL, not only are you not a real RDBMS but you can't even start without making your users' life misserable.

Connection timed out on all their servers?!

Yea, it was difficult. So difficult that I had to extract the sources from a zipped project file, put them into archive and rename to jar file. And hope that the versions I'm using are mathing....

The JBoss jar says it's implemented by JBoss.
JBoss/hibernate-entitymanager.jar/META-INF/MANIFEST.MF:

Manifest-Version: 1.0
Product: Hibernate EntityManager
Specification-Title: JBoss
Created-By: 1.5.0_09-b03 (Sun Microsystems Inc.)
Specification-Version: 4.2.2.GA
Implementation-Vendor-Id: http://www.jboss.org/   WTF?
Version: 3.2.1.GA
Implementation-URL: http://www.jboss.org/
Ant-Version: Apache Ant 1.6.5
Implementation-Title: JBoss [Trinity]
Specification-Vendor: JBoss (http://www.jboss.org/)
Implementation-Version: 4.2.2.GA (build: SVNTag=JBoss_4_2_2_GA date=20
 0710221139)
Implementation-Vendor: JBoss Inc.

However, the JBoss source does not have the sources.
http://repository.jboss.org/hibernate-entitymanager/3.2.1.GA/
WTF number 2?


In the hibernate downloads the source is missing as a separate download
http://sourceforge.net/project/showfiles.php?group_id=40712&package_id=156160
WTF number 3?

Finally, found it in the zip file in the last link. I was desparate, thinking of using the repositories here:
http://anonsvn.jboss.org/repos/hibernate/entitymanager/tags/
Had to extract it, re-zip it and hope the versions match. So far so good.

Why does it have to be so difficult?!

I want to override that api.org.hibernate.Interceptor#postFlush(java.util.Iterator)
I want to do it like that:
Does not work - the method is not with the same signature ?!

Then:
Does not work - the method is not with the same signature ?! WTF?

The only thing that does work (without a silly warning) is that:

Why?!!

How an iterator works:


Well, I want to move the red line in the loop init, so it would not mingle with the loop body where only business logic would reside.

Unfortunately that cannot happen. A for loop first inits the data, then checks the condition. With an iterator one has to first check if there are elements, then to get them.

And why would someone give you an iterator instead of a collection, my mind cannot understand. (org.hibernate.Interceptor#postFlush(java.util.Iterator))

JUnit spec (not very easy to find) states, that if there's an exception in the @Before method, the test is not called. True. BUT

JUnit spec does not state that in this case the @After method is called.

JUnit spec also does not state that if there's an exception in both the @Before and @After methods, the second exception (guess which one) overrides the first one. In my case the first one causes the second one (the first one is ConnectionClosed or similar, the second one is a NullPointerException because the resource is not initialized).

So the real reason for the problem is lost. One will say - avoid exceptions in the @After method - that's what I just did (and the real exception was printed), but finding the reason for that was not easy and straightforward.

I'm using junit 4.4, the default runner is JUnit4ClassRunner, JUnit4ClassRunner is calling ClassRoadie.runProtected():


This is the reason for the mentioned override. I hate when finally does that.

First, what's my goal
I want to do an audit log. I read the http://www.hibernate.org/318.html and there two different approaches were mentioned.
The first is using a Listener.
The second is using the new eventing model in Hibernate3.
The author said that he couldn't make the eventing approach work for an unknown reason.

I'm using Hibernate via JPA. I'm using it in an EJB. So the problem with the first approach is that it is difficult (if possilbe) to supply the same transaction to the interceptor so that it can write an entry in the audit log. There is a solution with a static field holding a session or an EM, but that seems ugly.

So I chose the second approach. I created a class, inherited few eventhandlers (PreInsertEventListener, PostUpdateEventListener ) and tried to add the class as a listener.

Using the API, it worked (the callback methods in the listeners were called):


Using properties (as if using persistence.xml) failed(the callback methods in the listeners were NOT called):


Ideas why?

I have to keep it alive for 24 hours. It's gonna be hard

Update: It's done - I successfully returned the dog alive, unharmed and in good condition.

Today I passed the exam for category A (motorcycles above 50cc). Very happy.

There's a trend - there are a lot of articles here in which I bitch about something. So there should be a category called 'Sucks'.

Update: reviewing the articles I found a lot of candidates for the category, it comes out that all I'm doing is bitching about stuff - I should change the subtitle of the blog :)

When one implements an interface, the template in Eclipse puts an @Override and it does not complain about it. Ant javac task also compiles without warnings.

Sometimes other Eclipse instances start to complain exactly for that @Override stating that there's no method that's overridden. Well, Eclipse, please do make up your mind.


Well, that's not very clear. As far as I remember an Interface is a pure abstract class, right? So, which one's correct.

P.S. Sometime ago I was having a similar problem with Eclipse and generics - Eclipse only gave a warning about something (can't remember what exactly), but the javac said that it was an error - Google said something like "eclipse uses jikes, you use javac". So what, aren't there specs?!


Update: apparently JDK5 (or 1.5, suit yourself) does not allow that. So in order to get all the wrong @Overrides - set the Compliance level to 5.0 (Eclipse -> Window -> Preferences -> Java -> Compiler -> Compiler compliance level ) - and..... correct them. I have 29 left.

All the referrers to this blog from live.com come like that:
http://search.live.com/results.aspx?q=class&form=QBHP or
http://search.live.com/results.aspx?q=interface&form=QBHP

The search word seems to be only 'class'. I can't believe that I come out in a search for only the word 'class'. I guess all the other words from the search are stripped which, if on purpose, is stupid, and, if not, ignorant.