Senior Software Developer

New software developers are often asking themselves, and others, what is it that makes developers to be considered senior?
Some senior developers, also ask themselves if and why they are considered senior (usually when they are seeking a new workplace).
Is there a list of things that I need to do in order to become senior? I would say No, and yes. Well there is no algorithm to measure how much senior a person is. Seniority is a matter of experience. And yes, there are a few ways of gathering experience.

I laugh everytime I see the distinction of senior developers as those having 5 years of experience or more. Imagine a guy who started working on his first job on the 1st of July 2011. He should be very happy right now, because in 3 days he will be baptised "a senior", as it will be the 5th anniversary of his carreer.

I will try to summarize my thoughts here. Here we are with some pragmatic points I consider as general directions to what exactly software development experience is. And everything in this list comes with a lot of experience:

• to know and recognize software design patterns
• to know and apply what is known as best practices
• to have holistic view of the solution or system or application
• to be up to date with existing and new technology developments
• to have the ability and mood to test and measure different things while designing a solution
• to be able to define the trade of technicalities with business needs and time management

Experiment as a word contains the word experience. That's what experiencing things mean. Experience means conducting experiments, and an experience software developer is the one who has experimented a lot. And of course your experiments should be based upon experiments of other people. The programming languages you use, the libraries, the frameworks and the virtual machines are (successful or not) experiments of other people. If you are not based on others' experiments, then you would need to experiment on whether "if" works as it claims, or whether "for loop" loops exactly the number of times it should!

You get some sort of experience when you are reading a book or an article about a technology, but still, this experience is far from conducting an actual experiment.
You are actually reading the procedure and the results of an experiment that was conducted by someone else. That's not bad. It's great!

That said, the most purely experienced software developer is not the one who has read a lot. It's most probably the one who have participated in a lot of different projects.

I know people who are working on the same project for years. I can't say they are not experienced. They have achieved to master another aspect of the experience: "deep" experience is often mentioned.
This is the kind of experience that can probably be referred as "specialization". And of course, "deep" experience or specialization does not come by itself... You have to mention right after "what" this "deep experience" or "specialization" is in. I mean you must be specialized in something, right? It's quite contradictary to be specialized in something that is abstract or too general...

Last but not least: have in mind that keeping up with a project for years means that it's complex enough, at first, and above that, it keeps your interest high, it's challenging. In other words, it has to be an evolving project. Otherwise, you will be "specialized" or "deeply experienced" in such a small amount or range of stuff that could make you feel embarassed.

SQL testbed sqlfiddle.com

First impression

I 'm so much impressed by this service www.sqlfiddle.com that I wanted to tell everybody about this. I discovered it through some questions and answers in stackoverflow, and I found out that it exists since 2012. I have seen several fiddles that enable online testing of other languages, but the magic of this one is that it's about databases, and you need to create and store your schema also. Moreover, you can choose among the main Database types and providers to test.

The problem(s)

I always wanted a test database server available and accessible from my PC to test different scenarios of tables, joins and performance of queries. I know it's nearly impossible to have installed Oracle, MySQL and MS SQL server on the same PC and test whatever you like... not to mention that some times the needs are to test on a specific version.

So, I was trying to find alternatives from buying a subscription to cloud services for all the above different DB vendors. Not to mention that I was thinking I could develop something like a test-bed and push it to the cloud... Fortunately, I recently found-out that somebody else did that.

Problem #1

You have a problem with a query for a client running Oracle. You are on the go and you don't have access to your development environment (of course) and you want to test the diagnostic query you want to send them before you send it (of course).

Problem #2

You have a brilliant idea on how to model your data and implement a special feature. But you don't have access to the development environment and even if you had, you don't want to bother with administration and installation of a DB server on your laptop. You just want to write SQL.

Problem #3

You want to help somebody in stackoverflow who is asking for help on a database-design SQL problem, or you may want to ask for help. The person who wants to ask for help can create a sample database schema and provide a query. That will be very convenient for other people wanting to help and reproduce the problem, as well as to test their suggested solution.

Solution

All you need is:

1. to access www.sqlfiddle.com
2. to select the corresponding DB server vendor and version. The supported databases list:
• MySQL 5.6
• MySQL 5.5
• Oracle 11g R2
• PostgreSQL 9.3
• SQLite (WebSQL)
• SQLite (SQL.js)
• MS SQL Server 2014
• MS SQL Server 2008
3. to provide a schema creation script (or have it saved with a link)
4. to provide a test data creation script (or have it saved with a link also) 

That's all. You are ready to test your diagnostic query before you send it.

More specifically:

Step 1: Select the corresponding Database and version.

Step 2: Provide the test schema creation script, and the sample data insert statements, on the left pane, and click on "Build Schema" button.

If the DB schema creation script has errors, then they will be reported at the bottom pane. If everything is fine, then the schema is created, and the right pane is activated where we can start testing our diagnostic queries.

Step 3: Ready to test your diagnostic query on the right pane. And the results appear on the bottom pane.

At the left pane, a schema browser is also available when clicking on the "Schema Browser" button. And as the results are presented in the bottom pane, a link for the "Execution Plan" is also available. What else to ask for?

Last but not least

You are thinking that sometimes you have to create a hundred of tables in order to replicate a database and address a special issue that you have. You are right, that's why www.sqlfiddle.com allows you to save your schema by keeping the link. And then you can access it from anywhere you have access to the Internet. For example, you can check the example I created for this post: http://www.sqlfiddle.com/#!9/5adfe.

The service also offers a free subscription option using authentication through Google+. This feature allows the user to maintain a list of schemas and queries under his account.

Credits

The project has been developed and maintained by Jake Feasel and it's open source at: https://github.com/jakefeasel/sqlfiddle2.

More information at: http://www.sqlfiddle.com/about.html.

In the future

I wish this service keeps up to date with latest versions of RDBMS. Moreover, a nice to have feature would be if I could choose to provide Java code with JDBC on the right pane.

However, if you need to test your Java JDBC code on MySQL, then there is http://www.tutorialspoint.com/compile_jdbc_online.php for this purpose. A review of this service is coming soon.

Rollback a specific commit and replace with the correct one - in git

For a specific task I should delete some files, move some others and update some more.
I committed something that was not completely correct (commit A). I needed to delete that commit and create a new one, to replace the old commit.
My options were:

1. to amend the commit (commit A) by making some corrections
(commit Y) <=================================== master
   |
   \
    -(commit X)-(commit A) <================ my-branch-name

2. to create a reverse commit and create a new correct commit (results in multiple commits)
(commit Y) <=================================== master
   |
   \
    -(commit X)-(commit A)-(reverse commit A)-(commit B) <== my-branch-name

3. to reset to the commit X, create a correct commit (commit B) on it, and then reset the HEAD of my-branch-name to that commit.
(commit Y) <=================================== master
   |
   |                     (commit A)
   \
    -(commit X)-(commit B) <================ my-branch-name

Option 1: amend previous commit

Option 1 would be as follows:
On top of the erroneous "commit A" I should provide all the corrective actions, stage them, and then amend the previous commit:
    git commit --amend

Option 2: create reverse commit

Option 2 has the below defects:
        * There were multiple deleted and moved files. It wouldn't be optimal to create a reverse commit and reapply my changes, since the commits should be squashed later.
        * The final changes should be included in a single commit, not multiple.

Option 3: reset to a specific commit

Option 3 is the most elegant and appropriate solution, especially when the changes are created by a script.

E.g. on the first run, the input of the script caused some changes and the commit A has been created. After that, new entries for the input of the script are coming. Then instead of finding which changes are not yet committed with commit A, it's better to reset to the previous commit, and execute again the script with the full new input. This will create a new complete set of changes that can be included in a single commit.
Execution of the script created changes A, B, D, F and G. All these changes are included in a new commit: "commit A". "Commit A" is the HEAD of my-branch-name.
New extra input to the script creates changes A, B, C, D, E, F and G. Imagine that this list could include thousands of entries. It's not easy to find the differences between the lists of changes and amend the "commit A".

To remove from the history my last erroneous commit (commit A), I need to reset the current branch to one commit backwards:
        git reset --hard HEAD~1

Perform the correct set of changes, and commit (commit B)
        git commit -m "comment for commit B"

To reset the current branch HEAD to the correct "commit B", that is not shown in git log, I can find the sha1 id of that particular commit executing:
        git reflog
       
And to reset the HEAD of my-branch-name to that commit I execute:
        git reset --hard <commit-B-sha1>

Connecting your codenvy development environment with a bitbucket git repository

Intro

Find below step-by-step information on how to connect your codenvy development environment with a bitbucket repository using SSH with a SSH key generated by codenvy.

1. Codenvy (generate SSH key)

Having a project open -> window -> Preferences -> SSH keystore -> Generate key -> the aplication asks for a url: give bitbucket.org
It generates a new line in the list of SSH keystore with the host label bitbucket.org (as you gave it)
Press the view button of that line, and the SSH key will be presented to you.
Copy all the content of the message box - including the initial 'ssh-rsa' string and the final 'email@address.com'.

2. Bitbucket.org (add the key to your account)

Account -> SSH keys -> Add key
On the popup window type 'bitbucket' in the label text field, and in the key field paste the generated key from codenvy.

3. Codenvy (add a remote git repository to your project)

Git -> Remotes -> Remotes -> The remote repositories message box includes the already declared remote repositories.
Press add, and in the pop-up window, give the name 'bitbucket' in the name field and type: ssh://git@altssh.bitbucket.org:443/<accountname>/<reponame>/ as described in this page: https://confluence.atlassian.com/display/BITBUCKET/Use+the+SSH+protocol+with+Bitbucket
Where accountname is your account name in bitbucket, and reponame is your repository name in bitbucket.

VDSL @home

Intel Edison on my hands

I managed to order the new intel embeddable SD card sized computer from sparkfun.
https://www.sparkfun.com/products/13024

I hope I 'm between the first ones who got it in Greece. It cost 40 euros as a product, 18 euros for postage from US, and finally 46 euros for complete import customs.

Morse code LED - light emitting diode - with Raspberry pi

More than interested in embedded platforms and microcontrollers, I acquired my 2 Raspberry pis full of enthusiasm, waiting at the end of long priority queues.
I downloaded some linux SD card images, I played with Rasbian and XBMC.
My enthusiasm faded out as I had not enough time to tinker more.
In the first months of this year (2014) I found out that Oracle was offering a training exactly on my needs. Using my preferred programming language, Java, a Raspberry pi, and some additional electronic components, a cutting edge project will educate as about embedded computing. This is the perfect chance for me to learn some things I always wanted to.
Unfortunately, I couldn't manage to follow the training, due to other running things.
But, I enjoyed their decision in Oracle to offer the material open to the public with unlimited access. Thank you guys!

Working with the training videos, I found out:

• how a breadboard works
• what are these breakout circuits
• several configuration issues on linux
• programming I/O pins of Raspberry pi using Java ME API

The most helpful tutorial on configuring the development environment with Raspberry pi and Rasbian is found here: http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/RaspberryPi_Setup/RaspberryPi_Setup.html. I found this link on the supporting material of the training course.

It's great! And it's even easier than I thought it could be.
The first hands on project was to blink a LED driven by the Raspberry pi. I found that it may be too easy, and I thought that it would be far more interesting to implement a morse code generator.
Given a message, the machine should blink the LED with Dits and Dahs, and the result would be a correctly transmitted message translated into morse code.

I found the morse code rules at: http://www.colorpilot.com/morse.html

The code for the MIDLet is as follows:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

import javax.microedition.midlet.MIDlet; /** * * @author stavros */ public class TestLed extends MIDlet { MorseDevice dev; @Override public void startApp() { String message = "SOS"; System.out.println("Starting playing message: " + message); dev = new MorseDevice(); dev.setMessage(message); dev.start(); } @Override public void destroyApp(boolean unconditional) { System.out.println("Finished playing message..."); } }

The code for the morse machine is as follows:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82

import java.util.Map; /** * * @author stavros */ public class MorseDevice extends Thread { private final static int UNITMS=200; private GPIOLed led; private String message; public void setMessage(String message) { this.message = message; } private Map<String, MorseCode[]> map = MorseCode.getMap(); @Override public void run() { led = new GPIOLed(18); for (int i=0; i<message.length(); i++) { char character = message.charAt(i); if (character == ' ') { // space has been handled } else { MorseCode[] code = map.get(String.valueOf(character)); play(code); if (i < message.length()-1) { char nextchar = message.charAt(i+1); if (nextchar == ' ') { wordpause(); } else { letterpause(); } } } } } private void play(MorseCode[] code) { for (MorseCode c: code) { this.led.on(); delay(c); this.led.off(); delay(UNITMS/20); } } private void wordpause() { delay(7*UNITMS); } private void letterpause() { delay(3*UNITMS); } private void delay(MorseCode mc) { if (MorseCode.DIT.equals(mc)) { delay(UNITMS); } else if (MorseCode.DAH.equals(mc)) { delay(3*UNITMS); } } private void delay(int milliseconds) { try { sleep(milliseconds); } catch(InterruptedException ie) { System.out.println(ie.getMessage()); } } }

The morse code encoding class is as follows:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55

import java.util.HashMap; import java.util.Map; /** * * @author stavros */ public enum MorseCode { DIT, DAH; public static Map<String,MorseCode[]> getMap() { Map<String, MorseCode[]> map = new HashMap<>(); map.put("A", new MorseCode[]{DIT, DAH}); map.put("B", new MorseCode[]{DAH, DIT, DIT, DIT}); map.put("C", new MorseCode[]{DAH, DIT, DAH, DIT}); map.put("D", new MorseCode[]{DAH, DIT, DIT}); map.put("E", new MorseCode[]{DIT}); map.put("F", new MorseCode[]{DIT, DIT, DAH, DIT}); map.put("G", new MorseCode[]{DAH, DAH, DIT}); map.put("H", new MorseCode[]{DIT, DIT, DIT, DIT}); map.put("I", new MorseCode[]{DIT, DIT}); map.put("J", new MorseCode[]{DIT, DAH, DAH, DAH}); map.put("K", new MorseCode[]{DAH, DIT, DAH}); map.put("L", new MorseCode[]{DIT, DAH, DIT, DIT}); map.put("M", new MorseCode[]{DAH, DAH}); map.put("N", new MorseCode[]{DAH, DIT}); map.put("O", new MorseCode[]{DAH, DAH, DAH}); map.put("P", new MorseCode[]{DIT, DAH, DAH, DIT}); map.put("Q", new MorseCode[]{DAH, DAH, DIT, DAH}); map.put("R", new MorseCode[]{DIT, DAH, DIT}); map.put("S", new MorseCode[]{DIT, DIT, DIT}); map.put("T", new MorseCode[]{DAH}); map.put("U", new MorseCode[]{DIT, DIT, DAH}); map.put("V", new MorseCode[]{DIT, DIT, DIT, DAH}); map.put("W", new MorseCode[]{DIT, DAH, DAH}); map.put("X", new MorseCode[]{DAH, DIT, DIT, DAH}); map.put("Y", new MorseCode[]{DAH, DIT, DAH, DAH}); map.put("Z", new MorseCode[]{DAH, DAH, DIT, DIT}); map.put("0", new MorseCode[]{DAH, DAH, DAH, DAH, DAH}); map.put("1", new MorseCode[]{DIT, DAH, DAH, DAH, DAH}); map.put("2", new MorseCode[]{DIT, DIT, DAH, DAH, DAH}); map.put("3", new MorseCode[]{DIT, DIT, DIT, DAH, DAH}); map.put("4", new MorseCode[]{DIT, DIT, DIT, DIT, DAH}); map.put("5", new MorseCode[]{DIT, DIT, DIT, DIT, DIT}); map.put("6", new MorseCode[]{DAH, DIT, DIT, DIT, DIT}); map.put("7", new MorseCode[]{DAH, DAH, DIT, DIT, DIT}); map.put("8", new MorseCode[]{DAH, DAH, DAH, DIT, DIT}); map.put("9", new MorseCode[]{DAH, DAH, DAH, DAH, DIT}); return map; } }

The code for the LED is as follows:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

import java.io.IOException; import java.util.logging.Level; import java.util.logging.Logger; import jdk.dio.DeviceManager; import jdk.dio.gpio.GPIOPin; /** * * @author stavros */ public class GPIOLed { private GPIOPin pin; public GPIOLed(final int pin) { try { this.pin = DeviceManager.open(pin); } catch(Exception ioe) { System.out.println(ioe.getMessage()); this.pin = null; } } public void on() { try { this.pin.setValue(true); } catch (IOException ex) { System.out.println(ex.getMessage()); } } public void off() { try { this.pin.setValue(false); } catch (IOException ex) { System.out.println(ex.getMessage()); } } }

Finally, this is a picture of the breadboard connected with the raspberry and the green light: