Creating the Keystore

Creating a keystore to store certificates that JBoss can use.

keytool -genkey -alias $MYDOMAIN -keyalg RSA ↵
-keystore my.keystore

You will be asked for a password to this keystore, just set any password you like. Furthermore you will need to enter some more information, just enter whatever you like – you only need these values to be correct if you are going to sign the certificate at your Certificate Authority.

Creating a Certificate Request

Then we need to create a Certificate Request.

keytool -certreq -keystore my.keystore ↵
-alias $MYDOMAIN -file myserver.csr

Normally you would want to send this Certificate Request to your Certificate Authority to sign it. That way browsers would accept your certificate without complaining. But we only need this certificate for our local development machine, so don’t worry about a security exception. You need to accept this certificate within your browser, though.

Configuring JBoss

You need to change this file to enable SSL with our created certificate: $JBOSS_HOME/server/default/deploy/jbossweb-tomcat50.sar/server.xml. Look for the following lines and uncomment them:

<Connector port="8443" address="${jboss.bind.address}"
  maxThreads="100" strategy="ms" maxHttpHeaderSize="8192"
  emptySessionPath="true"
  scheme="https" secure="true" clientAuth="false" 
  keystoreFile="${jboss.server.home.dir}/conf/ssl/my.keystore"
  keystorePass="KEYSTORE_PASSWORD" sslProtocol = "TLS" />

At last we need to copy your keystore to the proper place:

mkdir $JBOSS_HOME/server/default/conf/ssl
cp my.keystore $JBOSS_HOME/server/default/conf/ssl/

After a JBoss restart you can now use the https connection.

See also

This how-to is a short version of SSL mit JBoss (german).

I prepared a set to help me explain what I’m talking about. Correct gift wrapping 1 shows the material needed:

• wrapping paper
• scissors
• sticky tape
• the gift, respectively
• patience (at least with my descriptions)

I’m using a book here, but you could use anything else that’s not too abstract (like a statue or a teddy bear). In fact, this method works best with objects that are (close to) cuboids.

Cutting the paper

Put the book at the edge of the wrapping paper, leaving a three finger margin around the borders. Now cut through the longer side for about a bit more than two times the width of the book (see Correct gift wrapping 2 if I haven’t made myself clear). Don’t worry if you’re not good at cutting – it will never be seen since we fold this part to the inside.

Now put the book at the very edge of the paper (avoid rotating it). Memorise the position of the right border and move the book to the left until the left side is at this position. Add the thickness of the book two times plus three additional fingers in the same direction (see Correct gift wrapping 3). Now make a cut from the bottom to the top. This cut and the previous one should meet at one point (since this is almost never the case, do it as good as you can).

Congratulations! If you made it this far you can now put the scissors away and start folding (my favourite part).

Folding the wrap

Unless this piece of wrapping paper has never been used before there could be a slight chance that the left edge is not a straight line. This is not very nice since this edge is going to be visible from the outside. Don’t worry, there’s a solution to this. Make an inside (valley) fold the width about half a finger to the inside (see Correct gift wrapping 4 for visualisation). That way we get a straight line at this edge. Now relax and enjoy for a while.

OK, we’ve created a straight edge at the left side. Now wrap this edge around the book. Position the book so that this edge and the left edge of the book make a line (see Correct gift wrapping 5). The paper should lie flat on the book. Don’t move the book on the paper, the book should keep this position on the underlying paper. Relax the folded edge but make sure the book doesn’t move.

That the right edge of the paper and wrap it over the right side of the book. It should lie flat on the book like the left edge was lying flat before. If you like (and if the surface of the book allows it) you can put some sticky tape to fix this edge to the book. I couldn’t do it since the surface of this book didn’t allow it. In fact, the book would have been harmed if the tape is removed. Think about it.

Here comes another tricky part. Put the left edge, that we folded before, and wrap it around to the right side of the book (where the right edge should now cover part of the title page of the book). This edge and the right edge of the book should again make a line. If it does, put sticky tape across to fix this part (a width of about two fingers should be enough to do the job). Your half baked gift should now look like the one on Correct gift wrapping 7.

Folding the top

Center the book in its paper wrapping. Rotate the upper side to you. Put the fingers of your left hand at the upper edge of the book and make sure the book doesn’t move (see Correct gift wrapping 8). You should try to make a crease in case the book accidently moves. This way you won’t lose the actual position of the book.

Take the edge that is closer to you (like the one on Image 8) and move it to the center of the books upper edge. Look at Correct gift wrapping 9 for what you should be doing. This is also a tricky part since the paper doesn’t always do what we want. You have to be careful, try not to move the book. Make a crease where horizontal and vertical parts of the paper meet (see Correct gift wrapping 9). Fold the edge of the new diagonal part flat on the table.

If you could do the last two steps the next two shouldn’t be a problem. The same procedure as before, rotate the book clockwise so the other edge faces you (like Correct gift wrapping 10 shows). You already know what to do, but I’ll guide you through it anyway. And I’m still smiling ;).

We use our thumb to fold the paper across the right downward edge that is facing us (see Correct gift wrapping 11, also see Correct gift wrapping 8 for additional help). Fix the book so it doesn’t move (I can’t stop saying this since it happens all the time and is frustrating and demotivating).

Fold the newly created diagonal flat on the table. Your wrapped book should now look like mine on Correct gift wrapping 12.

If the two diagonals and the upper edge of the book doesn’t describe a triangle but a trapezium – don’t worry. This happens either if your margin was less than three fingers or you are Kate Moss. The next steps will still work for you.

If you happened to take more than three fingers width as margin around the book then unfold the last few steps which created the diagonals. Then take the scissors again and cut away approximately the width of one finger from the upper edge. Fold in the edges and check again. Redo as often as needed.

Take the corner that was created by the two diagonals and fold it inside (valley fold) to the upper edge of the book (see Correct gift wrapping 13). In fact the corner shouldn’t touch the upper edge. It is easier for you to fold it upside when there is some buffer left.

Repeat the last step as often as needed. Stop if the width of the folded part is less than the thickness of the book. I had to do it a second time. If I used a smaller margin around the book at the beginning then it would have taken me less time to wrap up my gift. But who am I sporting here, dude?

Correct gift wrapping 15 shows how to fold this part to the upper edge of the book. Again, don’t move the book! Freeze it with one hand and use the other to fold the thing. Press the book from the open side to this fold to create some tension. This step is needed so your gift looks like wrapped up in wrapping paper and not in a paper bag.

Put sticky tape on the edge so you fix the part you folded. Don’t use too much tape, the gift might look like you only used tape to wrap it ;). Also, if the tape is carefully removed you can eventually reuse this piece of wrapping paper (to put a book in there the same size, but half the work).

Folding the bottom

The upper edge of the book is finished. As you no doubt already guessed – same procedure on the other side. Rotate the book so the bottom of the book now faces you. Take the left edge and… You know how to do it, don’t you? Use the next images to look how I did it.

The finished gift

This is how your gift should look like when you’re finished. If it isn’t as good as you wanted it to be then don’t worry – as long as it was made by yourself the receiver will respect your effort. And the next one will get better, trust me. All that is left to say now is: have fun wrapping!

If you have any suggestions on how to improve this how-to let me know. Also let me know about corrections on the article or on the images.

Note: I know what book it is since it was me who wrapped it up. But the person this gift is meant to doesn’t, so please don’t tell what the title of the book is nor who wrote it. At least until Christmas eve. :)

Why Sudoku?

I like Sudoku. With Sudoku you have to turn your concentration completely off from anything else. Sudoku makes me use my brain, which I frankly don’t use a lot these times. It is a complex game with a few easy rules that in my opinion makes it the best puzzle these days.

Rules

Sudoku consists of a 9×9 grid with nine 3×3 boxes in it. Each column, row or 3×3 box has to filled with the digits from 1 to 9. Every digit must exist exactly once in each column, row and 3×3 box. You start with the numbers given.

Tips

If you begin solving Sudoku puzzles you may take a pencil and write down the possible digits for each field. This is very time consuming and may lead to confusion when there are a lot of choices left. Better try to think of this: if a digit already exists in a certain row then it can’t appear again in this row. Then find another row within this 3×3 box the first row appears to be in and look for the same digit. If there exists such a second row, then the third row of this 3×3 box has to hold this digit too. And this can only be in the 3×3 box, where this digit doesn’t already exist. I’ll give you an example.

Sudoku example

This is the base grid. The grid consists of 9 columns, 9 rows and 9 3×3 boxes. Each box has a number in it such that it can be referenced for further explanation. This sample grid is filled with 29 given digits. The amount of given digits does not neccessarily tell us the difficulty since a good combination of fewer number may or may not be easier to solve than a hard combination of more numbers.

I’ll use the colour red to highlight rows or columns that already have a certain digit in them. A highlighted blue row or column indicates a new digit will be placed in this zone. This digit itself is blue and has a blue marking around. Newly inserted digits will be coloured black in the next step to minimise confusion.

Step 1

Look at the image at step 1 (Image 3). As you can see there are two rows highlighted in red that indicate the two rows containing a digit (in our example it is the 3). The 3×3 boxes that are of our interest are 7, 8 and 9. In box 9 the digit 3 is missing, and it may not be inserted in a highlighted field (since that row already has 3 in it). This way the only field left in box 9 is the one centered at the bottom.

Step 2

This step basically does the same as the first step (see Image 4). Instead of 3 the interesting digit will be 7. And this time we will use columns instead of rows (which of course doesn’t matter). The 3×3 boxes 3, 6 and 9 are highlighted, but only the middle one (box 6) fails to have 7 in it. The only field in box 6 left obviously is the one at the top left.

Step 3

This is a tricky step. You see a lot of rows and columns selected. First look at box 7: it contains 7 at the very left, this columns is highlighted. Now take a look at box 6: the containing 7 lives at the top of this box, this row is highlighted. This leaves us the following choice in box 4: either put 7 at the very center field of this box or at the bottom center field. Either way, you do not write any digit in this box. The only thing you have to know is that this center column has a 7 in it (box 4) and the other boxes (1 and 7) must not have a 7 at the centered column. That is the reason this column is also highlighted. And because there’s a 7 in box 2 at the top row and a 7 in box 3 at the bottom row the only field left for 7 in box 1 is: You got it! The middle right field.

This way you can fill up a lot of empty places with digits. You might fill up everything with this technique, but you may as well get stuck at a point with too much choices to handle. Then I go back to the good old write-the-choices-in-a-space-and-go-on. Sometimes I discover something I haven’t seen before. Just do not use trial and error techniques.

Where to next

Sites that give you good Sudoku. Whenever I find a site with good Sudoku puzzles I’ll add it to this list.

• derStandard.at
• The Times Online
• Too good for Fiendish?
• Sudoku.com (has a tutorial too)

Acknowledgements

The images where made by myself with The GIMP. I used the given digits from a Sudoku puzzle from derStandard.at.

I’d like to provide a few tricks for VIM, mainly commands I find very useful to work with. All of the commands are to be typed when using command mode (press [esc] to ensure you are in command mode), except when I say otherwise.

Most common commands

i insert text to the left of cursor (change to insert mode) I insert text at beginning of line a append text to the right of cursor A append text at end of line [esc] switch to command mode (being in insert mode) w write to file q quit q! force quit (don’t save) cw change word dd delete line D delete until end of line r replace character R replace mode (like insert mode, but overwrites existing characters)

Undo, Redo and Undo Undo

u undo last action . redo last action [ctrl]+r undo undo action Highlight, cut, copy and paste text v select characters of text V select lines of text Y copy selected text p paste copied text after this character/line P paste copied text before this character/line

Changing case

gu{motion} make lowercase gU{motion} make uppercase guu make line lowercase gUU make line uppercase

Substitute

can be any regular expression :s/pattern/string/ substitute first match of with within this line :s/pattern/string/g substitute all matches of with within this line :%s/pattern/string/g substitute all matches of with within this file v{motion}:s/pattern/string/g substitute all matches of with within highlighted selection

Splitting vim

:split path/to/file split window horizontal with path/to/file as second file :vsplit path/to/file split window vertical with path/to/file as second file [ctrl]+w w switch between viewports

Special Inserts

If you’d like to insert text column-wise, eg. to comment some things out, you could use this nifty trick:

1. [ctrl]+v{motion}: select lines/area where you want to insert text
2. I: insert text to beginning of selection on each line; alternatively use A to append text to end of selection on each line

Special Substitutions

%s/ ([a-z])=([^"][^> "}])/ 1=”2″/g creates “s around tag-attributes if non existing. makes from