Tag: programming

Your Maven Java WEB project in Eclipse WTP

2011-01-29 rolfje 12 Comments

In our company, all Java projects are setup with Maven configuration so that after a “mvn eclipse:eclipse” any developer is generally good to go. One of these projects was a web project but would not transform into a WTP project. By running “mvn eclispe:eclipse” it became a Java project, but could not be added to a Server in Eclipse. It was not a WTP project.

I learned that the author of the project tried but never got the WTP plugin to work properly. Using the Google, I found more people who are having the same problem converting their existing Maven Java Web projects in Eclipse into a WTP project. There are even a few desperate articles describing how to edit your .project and .classpath files. Oh dear. This calls for an article on www.rolfje.com.

Software

Simple Strict Date Parsing

2010-03-06 rolfje No Comments

In Java, the DateFormat.parse() method is a funny little critter. It helps you by trying to figure out what date you actually meant when you typed in “35/12/2O10” (note the letter “O” in 2O10). In this case, it will parse the date without errors or warnings, and returns the date “11/12/04” (November 12th, 0004). That’s because it thinks “35” is a month, and “2” is the year, ignoring everything after the letter “O”.

DateFormat tries to convert the “35th month” into 2 years and 11 months, and correct the date accordingly. df.setLenient(false) prevents this, but that still leaves the problem of the parsing stopping at the first wrong character without warning.

I needed a much stricter way of parsing dates, and yesterday I found an elegant solution to this problem. It’s so small I was able to tweet it in less than 140 characters, but I thought it deserved a decent blogpost so here it goes:


public Date parseDateString(String inputDateString) 
         throws ParseException {
  DateFormat df = DateFormat.getDateInstance(DateFormat.SHORT);
  Date parsedDate = df.parse(inputDateString);

  if (!inputDateString.equals(df.format(parsedDate))) {
    throw new ParseException("Invalid Date", 0);
  }
  return parsedDate;
}

The brilliance here is in the comparing of the formatted date with the original input. The method returns a normal ParseException so you can perfectly replace your original df.parse() calls with it, making them more strict.

Thanks to Bas for this elegant and simple solution.

Software

Ibatis Inline Parameter Maps

2010-02-16 rolfje 3 Comments

Today I (re)discovered a feature in the Ibatis data mapper framework which was clearly documented, but for some reason was not being used in our project. The feature is called “inline parameter maps” and combined with a wrapper bean it can clean up a lot of clutter in the code and in the SqlMaps. Please feel free to share this example with your fellow Ibatis Data Mapper 2 framework users.

Uncategorized

Flow

2009-12-22 rolfje 3 Comments

Being “in the flow”. The nicest state of mind known to mankind. You act without thinking, and everyone of your actions is the perfect response to the situation. Riding a motorcycle on a beautiful road without a destination can easily get you into this state. With an empty mind, you see the next 2 corners, feel your bike as your brakes hit the disc, smell the forest, and hear the wind as you start accelerating out of the first corner while naturally placing the bike into position for the next.

Sonar “Close Connection” warning workaround.

2009-10-06 rolfje 7 Comments

When you use Spring and Ibatis and SQLTemplates, you could have code in your project which looks somewhat like this:

Connection connection = DataSourceUtils.getConnection(getDataSource());
...<do connection stuff here>...
DataSourceUtils.releaseConnection(connection, getDataSource());

Sonar will report that you did not close the connection, while in fact, Spring did that for you. You can not just add a “connection.close()” to the code because the whole point of calling “releaseConnection()” is to have Spring handle all the smart stuff on committing, closing, and returning the connection to the pool if needed.

Software

Transactions and Isolation levels

2009-08-29 rolfje 2 Comments

At work, we have two applications which connect to the same database. For all kinds of business reasons, we need to make sure that only one of the applications accesses certain data at the same time. To do this, we use a row in a table as a semaphore.

While working on the locking mechanism, we had a closer look at the Transaction Management and the Isolation Levels we were using. There is a lot of good documentation on Transaction and Isolation, but it tends to be over complete, elaborate and therefore hard to read. I’ll try to share our insights with you in a slightly more digestable form (I hope).

Read More “Transactions and Isolation levels” »

Software

Starting Java app from Applescript

2009-06-11 rolfje No Comments

Suppose you have a Java Swing application which you can start by typing the following on the command line:

java -jar myTerrificSwingApp.jar

If you want to make that application start from the Finder in OSX, there are a lot of options which range from ugly to convoluted. If you need a quick fix, here’s how to do it.

Apple, Software

Javascript Window Shake

2009-03-12 rolfje 2 Comments

This evening I came accross the window.moveBy() JavaScript function and thought it would be cool to shake the browser window when a user fails to log in. It turns out that I was not the only one thinking this, but none of the examples worked for me. Some had no proper delays, others only worked from the page header, and some were plain unreadable.

I’m no Javascript guru, but I hacked this together which is working pretty nicely. It is in fact almost undistinguishable from the Apple login window shake at a login failure:

<script type="text/javascript">
if (window.moveBy) {
	delay = 70;
	shakes = 3;
	window.moveBy(-10, 0);
	for (j = shakes; j > 0; j--) {
		setTimeout( "window.moveBy(20, 0)", j*delay );
		setTimeout( "window.moveBy(-20, 0)", 
					j*delay+(delay/2));
	}
	setTimeout( "window.moveBy(10, 0)", (shakes+1)*delay );
}
</script>

In my case, I surrounded this code with a Tapestry @Conditional and made it into a reusable Tapestry component so that I can make any window shake as soon as it contains an error.

The code will work anywhere on your page, but I advise you to put it at the bottom of the HTML. This will make sure that the content is shown in the browser before you shake it.

It’s visually much stronger than just adding an errortext to the page. If people log in a couple of times a day, they don’t even notice extra text on the screen. This will “shake” them awake 🙂

Have fun!

Fun, Software

Care vs Careless

2009-02-03 rolfje No Comments

It’s frightening to realize how close to the truth Eric Burke is.

Fun

“Instruments” – Application monitor

2009-01-02 rolfje No Comments

Did you know that your installation of Leopard comes with a built-in performance monitor? It’s called “Instruments” and you can attach it to any process currently running. In the screenshot you see here I attached it to an instance of Eclipse while running some unittests.

Instruments has some nice templates for you to choose from, and you can monitor CPU activity per thread, disk I/O, User Interface activity, Object allocations, and leaks. Just so you know, it might come in handy.

Apple, Software