Head First Servlets and JSP Errata

I’m sitting another Sun* Certification exam tomorrow to become a Sun Certified Web Component Developer (SCWCD). I’ve done a bit of revising but I’m writing this post mainly as a way to procrastinate. I should take more exams really if only as a way to get other things done. Procrastination during my final year of uni enabled me to learn how to speedsolve a Rubik’s Cube.

I’ve just read the study guide for the SCWCD exam; Head First Servlets and JSP.

It’s quite long, and pretty good at sending you to sleep in the evening, but as programming books go, it’s good in the sense you can just read it without being sat at a computer.

I made a list of mistakes I spotted whilst reading the book almost like a game that made sure I read it thoroughly. O’Reilly offer a page for people to submit errata for this book but to be honest, I can’t be bothered. They should give people free books as a reward. Maybe if I mention the name “Kathy Sierra” in this post, she’ll find this from Google and post me a book herself 😉

p140 – in bullet 6 it should be “mostly
p315 – It says only four attributes are on the exam, but if so, it’s not clear which four.
p555 – an design principle
p557 – the size attribute disappears
p580 – directional quote marks are a problem throughout the book but the sample code in question 3 tries to concatenate a String that contains un-escaped quotes that can only end in tears.
p587 – valid uses of these tags
p590 – answer E is ticked even though it is incorrect.
p598 – the reason for Q17 option D is just badly phrased.
p599 – I don’t remember reading anything about the “variable” directive, did I fall asleep at that bit or have a got a page missing?!
p654 – A Brew Master gets special descounts
p677 – Missing T – CLIENT-CERT
p694 – Q1, option C has a space in front of it. This isn’t the only example in the book either
p710 – The book randomly applies ligatures for adjacent F and I characters. Annoyingly however, it does this in the “courier new” code examples which is chosen because it is a fixed width font. Blending F and I into a single charater width looks really strange to me. I picked p710 as an example because the first line doesn’t use a ligature, but the first bullet point does.
p747 – other client components
p777 – in the bottom right, the sentence doesn’t count all 5 jars
p787 – I don’ remember there being any talk of the Composite Delegate pattern in this book

Well, that kept me busy for a few minutes, I better take the mock exam and see how badly I’m going to fail this exam…

*I’m sure the Sun certification exams will be deprecated by Friday by a bigwig in Oracle towers.

How to fix the aspect ratio on videos from Windows Movie Maker Live

Problem:

wmv file looks squashed when played in VLC or when uploaded to youtube but looks fine when played in windows media player

Solution:

You can change the aspect ratio of a wmv file without re-encoding it with vmarchanger

Ok, hopefully you just searched for this and you’re now sorted, but here’s some background on my problem in case it helps.

I made a small video (640×480 50fps) on my 7D and wanted to slap it on youtube. I didn’t have any video editing software so grabbed Windows Live Movie Maker. After exporting the video file I found it plays in the wrong aspect ratio in all players but WMP. The app that fixed it was written by this crypto fellow over here. Thanks Crypto!

The real cause of the problem?

I didn’t use a mac.

A build that’s green, should never be seen.

Your continuous integration server should stay green all the time. The odd broken test here and there means you get numb to the failed status on your build server, which in turn means it takes you longer to notice that the build has broken. When the build breaks, you should stop whatever you’re doing and make fixing it your top* priority. After you check in, the faster you fail the better because you haven’t had time to start thinking about your next task, and the thing you did to break the build is still fresh in your mind. That’s also why it’s so import to keep the builds fast**.

At work, we’ve just installed the Radiator View Plugin*** for Hudson which allows you to see the status of all your builds at a glance. We have a spare monitor displaying this screen in the middle of the office so that you can see if the build has failed while you’re stood around the water cooler chatting about your coffee cup metric.

There are two things that still bug me about this though:

  1. That monitor is burning up quite a bit of ‘leccy.
  2. I don’t want to waste any thought power on a green build.

The first point is obvious but the second is a little more subtle. To me, no news is good news. A green screen in the middle of the office will still get my attention, when what I really want, is to pay it no attention whatsoever. That is, unless it’s red, which is when it gets all my attention. To achieve both of these requirements****, I want the screen off when the build is fine, and on when it’s not.

Introducing… screenwaker!

screenwaker is a silly little java webstart app I knocked up that polls the build page and turns off the screen if everythings ok, but fires it back up again if anything fails. Perfect.

I’m not sure anyone else has ever faced this problem, or ever will, but there it is for you to use as you please none-the-less.

Matt

* Yes, top priority. I don’t care if you were going to the loo.

** I searched for a good article on why it’s so important to keep the build fast but couldn’t find a good one. Suggestions welcome.

*** I don’t really get the “Radiator” analogy. Surely “Dashboard” would be better?

**** Well, in an ideal world, I’d like the monitor to disappear but that is beyond the scope of this post.

Should I buy a Canon 7D in the US and carry back to the UK?

Canon have just released the 7D and although I can’t really afford it, I have to have one!

The price difference between UK and US is pretty crazy. Here, my favourite camera shop are selling body only for £1,399. £300 less than Canon’s SRP. In New York’s B&H store you can pick it up for $1,699 (~£1,014).

As luck would have it, I’m going to NY this weekend so if I’m going to buy one, now’s the time to decide.

I saw some people on flickr discussing whether or not it was worth it, or whether you could get it through customs and so I decided to call them myself. I rang the VAT, Customs and Excise helpline and was told that it being a digital camera, it was not liable for import duty and I would only have to pay VAT (currently @ 15%). I would just declare it on arrival in the UK by going down the red channel.

I think I can get the US sales tax (~8.25% ?) knocked off the camera when I buy it if I show them my passport and tell them I’m taking it home, but I’m not sure about that. Please comment if you know…

UPDATE: I contacted them about sales tax:

Purchases in our store (and all stores in NYC) are subject to an 8.875% local sales tax. This tax is not a VAT, and cannot be recovered by non-USA visitors when returning home. All prices are listed before sales tax.

This brings the total to $1,850 (£1106), it means I can still buy the 7D for about £1,270 when you add the VAT. A saving of £130.

However, I’m also not sure the Canon warranty covers me outside the US.

UPDATE: I contacted them about warranty too:

The warranty on this product is only good inside the USA. We offer the SageMax Protection Plan which is good for worldwide warranty and accidental damage protection…

What would you do?

Read the blog post, read read. But what if I don’t want to? It doesn’t matter, READ!

After some late night cramming for an exam last week I went to bed with my head still chattering. I told a sleepy Karen about my day at work and how Dan and I kept singing different words to Adam and Joe‘s “Text the Nation” jingle. I gave the example: “Patch the source code, patch patch, but what if it’s not tested? It doesn’t matter, PATCH!” (I hope the sarcasm reads well).

As I noisily clambered into bed, Karen reminded me I still had my glasses on. “But how will I see my dreams?” I replied, to which she instantly quipped “It doesn’t matter, SLEEP!”. Karen got the idea instantly even though she was half asleep and doesn’t really listen to the show. She still managed to come up with something better than any of my attempts.

It’s when these moments of utter genius tumble out of Karen’s mouth that I am reminded how much smarter than me she is.

Convention ÷ Configuration

I’ve long been sold on the concept of Convention Over Configuration. For me it’s a no-brainer, not only am I lazy, but when I am forced to make a decision about something technical, well, let’s just say the number of times I get it wrong is > 0.

Recently I’ve been playing around with Maven, something I should have done years ago. Maven seems pretty sold on the convention idea too and so I just expected a simple project to work “out of the box”.

Unfortunately, when I tried, I hit a problem with my first simple project. As you can see from the “reconstruction” screenshot, I had problem with recognising simple java 5 features.

I was using the latest copy of eclipse, on a fresh install of Ubuntu using OpenJDK. I’ve not developed with OpenJDK and so blamed that at first, it couldn’t possibly be Maven… So, I downloaded the Sun JDK, and as you can guess, I realised it was a Maven thing.

When you create a simple Maven project using the m2eclipse eclipse plugin it defaults to a Java 1.4 compliance level. What kind of sensible convention is that? I like to think there is a good reason for that because I imagine it has cost the community quite a few potential Mavenees.

Once you realise this is the problem, just change the project specific Java compiler settings to whatever makes sense for you.

I’ve not got any research or references to hand, but my gut tells me that the convention should be to use whatever the majority of the programming community agrees is the best version of the best tool for the job. If someone wants to use Maven for a project that needs to support backwards compatibility, then let them do the configuring, not me.

It also defaults to JUnit 3.8.1, another warning sign in my head. Everything else in Maven I have done so far has been a pleasure and m2eclipse looks like a great plugin, I just wish the defaults were not so 2004.

To fix this within the POM you need to add the following:

<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>

</plugins>

What’s the best sim-only mobile contract?

OK, I know, it’s a bit of a silly question because everyone has different needs, but these are mine:

  • 1 month rolling contract — I don’t want to be stuck with the contract for 12 months
  • Keep my number — I rummaged through the boxes in a BTCellnet shop years ago to get my number and I’m going to keep it
  • Unlimited internet — Well, a fair usage of at least 1GB, and I don’t want to get charged if I go over, I just want a warning
  • Some free minutes — To all networks of course
  • Some free texts
  • £25 per month or less

So far, the best I’ve found is the solo-20 plan at T-Mobile:

  • 1 month rolling contract
  • Keep my number
  • Unlimited internet — Fair usage of 1GB
  • 600 minutes to all networks
  • Unlimited texts
  • £20 per month

If you think you’ve found a better plan that meets my minimum requirements, or this deal is no longer available, add a comment and I’ll update this post.

Update December 2012: This solo-20 plan is no longer available. This was pointed out to me by a commenter linking to http://www.comparisim.co.uk/. I thought, oh great, another spammer (like many of the comments) but the site actually looks pretty good. I also recommend http://www.billmonitor.com/. Personally I’m on a normal contract now (this post is old) but please post any good deals in the comments for others to find.

Cheers!

-Matt