May 18, 2010

GeeCON 2010 general impressions

GeeCON 2009 in Cracow was a wonderful experience, and this year Poznan held the conference. If you ever wonder whether GeeCON is worth the time and money, the answer is plain and simple: definitely yes.

I'm not able to give you a full review this time, as I'm leaving tomorrow for Paris, and I haven't prepared myself yet, but let me summarize the most important topics.

There were two different presentations about Erlang way (Actor and Agent models) of solving the problem with concurrency. One was a general overview of the problem and possible solutions running on JVM, and the other was about Akka Project/Platform that looks very interesting and above all, is simple to use (at least from what we've seen at the presentation). So far I've been trying to shield myself from concurrency problems with web servers, stateless services and optimistic locking on database level, but the solution presented here is really appealing. I'd love to try it out.

Joonas Lehtinen had a very nice lecture about Vaadin. There was a talk about Hades which is probably going to replace the solution I usually use (hibernate-generic-dao). Kuba Kurlenda is testing it on real project right now.

Stephan Herrmann was talking about an evolutionary idea for Object Oriented Programming:  Object Teams. This may be the next big step we need, but it would have to gain some momentum and find a real life use in a big project. Unfortunately Object Teams do not yet have a successful example to follow. The main question I see is whether it's worth investing the time of your team, while everyone already knows about design patterns, which solve similar problems.

There was a presentation about Spring Roo framework which is something you should know before you move to Grails or Ruby on Rails. Even if you do not plan to do it, it's a great way to create prototypes.

Waldemar Kot had a very condensed, content rich but easy to learn lecture about Complex Event Processing. It was definitely worth listening to. I'll try to infect my SQL friends with this idea, as it seems like something they would really like to do, when they move from PL/SQL to Java. Thomas Sundberg repeated his talk about Software Craftsmanship that he gave at Agile Central Europe. There was a little bit about Comet (push style Ajax), agility, OOP and lots of other interesting stuff.

And there was a great party, but that's a completely different story.

If you have a chance to go to GeeCON 2011, do not hesitate to.

PS: all the pictures come from the official GeeCON gallery. I don't know about the authors, though.

May 17, 2010

Open Code Review

Łukasz Lenart at Warszawa Design Patterns Study Group gave a very interesting presentation about Open Code Review in his company (you can read the details here). I've failed to notice whether it's his own idea, or somebody's else, but that's not as important as the fact how well it works.
Open Code Review, in short, is when a small group of programmers (up to 6) meet once in a while for a brainstorming session, take some printed out code, and try to find out, for an hour or so, what could be done better.
It's basically about sharing knowledge and insight with others. It can be a very beneficial experience, especially for teams that do not use Pair Programming, or to pairs that do not switch very often, but I think anyone can find it useful.

The power of this technique is reflection. When we code, when we create software, we often find ourselves thinking in a specific way. We tend to take things for granted. We start to look at the code with our mind set on a particular solution, and as a result, we can't see the forest for the trees. This is how human mind works, it's nothing new. After a few weeks of walking the same route, you stop noticing the buildings along the way.

It's also one of the reasons why Pair Programming is so efficient. “You cannot solve a problem with the same mind-set that got you into the problem in the first place”, as some believe Einstein said. Having another mind next to you, looking at the same code, gives a chance to spot the problem as it is being created, but more importantly, it is very helpful in the process of discovering the best design. Open Code Review works in a similar way. It allows you to learn different mindsets and different styles of solving problems. Nothing is as refreshing as being able to see from other points of view.

Apart from this, OCR meetings also help in spreading knowledge (people read different books) and experience (people work on different projects with different technologies and problems).

This idea inspired me to organize similar meetings at TouK and I've got very good feedback so far. Our formula crystallized by looking at the the past and finding out what was cool and what was not. Our take on Open Code Review is quite different to what Łukasz proposed.

But first, things that we do the same way: we take maximum 6 people (plus the moderator), we gather them up in a conference room, we hand out code printed on paper.

The code we take is not Open Source, as Łukasz suggested. His reasoning was, that if you take somebody's code, it could turn personal, we all put some heart into our work, after all. This is where we disagree: we have found it very valuable to take internal code from our projects. We are not afraid of our code being criticized. As Robert C. Martin wrote: every good programmer should get used to professional code review. Bad programmers can benefit from it even better. And if you have some Prima Donnas in your team, unwilling to hear constructive critique to their code... screw them. Nobody's able to work with them anyways.

Second thing we do differently, is that we do not comment the code on paper. We actually have a working environment (IDE and stuff) with three keyboards/mice, thanks to USB hubs. We either comment the code directly, writing TODOs, for bigger changes that would take more time than it's left, or we do the refactoring right away. This allows us to make a commit to the repository after the session and improve some project a bit. It's also much easier to talk about the code, when you have a keyboard at hand. Sometimes it's just way simpler to show what you mean than to explain it with words.

We also take a bit longer for each meeting: usually an hour and a half, or two hours. This is the optimum time, to learn and do something meaningful, and not get tired. And we do not split attendees into teams, we want people to talk a lot, and we want people to talk with each other.

So what is our recipe for an Open Code Review? It's like this:

  1. Invite anyone who wants to participate, from all over company, but take no more than 4 to 6 programmers plus a moderator
  2. Take a conference room with a laptop, three or four keyboards/mice, and a projector
  3. Set up the meeting for 1.5 or 2 hours
  4. Moderator prints out a class (or a few classes) that
    1. has between 150 and 300 lines of code
    2. has unit/integration tests for all non trivial methods
    3. is from a project that works with our environment (IDE/Maven etc.)
    4. is not trivial and not completely shitty (that would be too easy and nobody will learn anything)

  1. Give everyone printouts and 10 to 15 minutes to read the code and make notes
  2. Ask whether you should start top-down or from some other point in the code (some classes are broken conceptually and it's better to fix them by talking about their responsibilities first). If in doubt start from the top.
  3. For every block/method/property ask whether anyone thinks that it could be done better. The person that has the idea, has the power (keyboard) to do it.
    1. If it's a small change, fix the code
    2. If it's a big change that would take longer than the meeting, write a TODO
    3. If someone disagrees, talk, talk, talk until consensus is found or you agree that you disagree and move on
    4. Run (write if needed) tests, to make sure the code works. This is a real refactoring, you cannot break the code. Broken code is not considered better.
  4. If you cannot find anything more that you could get better, use the principles from “Clean Code” (or some other book) to guide you.
  5. At the end of the meeting, commit the code.

Things to remember

If you are the moderator, remember to shut up and keep quiet. You probably had a bit more time to read the code so it's natural you'll have noticed more flaws, but let the people do the exploration and discovery. When they don't have anything else to say, then it's the time for you to speak.

If you are the author, no matter what, DO NOT EXPLAIN the code. Either the code speaks for itself, or is badly written.


PS: this practice has been unfortunately stopped, because I've started to go to conferences and could not moderate any more. Do not make my mistake and communicate clearly, that ANYONE can call for an Open Code Review, and that the moderator should be changed every two weeks or so. I've failed at doing that, and now I have to revive the whole thing.

May 12, 2010

Boy Scout Rule in practice

I've started doing Scrum in late 2008 (thanks to Piotr Burdyło). And though I've immediately seen benefits of practices like daily standups, sprint planning, reviews and retrospectives, I had a big problem with finding out how to deal with refactoring within this method.

Before Scrum, whenever I found a place in code that I thought should be done better, I'd put a TODO comment. I would return to these comments whenever I saved some time on what I was doing, or when I decided that it has already been too ugly for my standards. And since my standards are pretty tight, I've been  (and making others) refactoring quite often and it worked well for me.

When doing code review, I'd write TODOs, discuss them with the authors of the code, and make them do clean up as the top priority.

But what were my options in Scrum?

1. Don't tell anybody, and just use your left over time to clean up the TODOs

This is against transparency, which Scrum is advocating, and against my moral backbone (no lying). And since you are evaluating tasks/features better and better, sooner or later you'll have no left over time for TODOs anyway. Ergo: this won't do.

2. Create additional tasks/features for refactoring

These are not visible from the product owner point of view, so some Scrum Masters are strongly pushing against them.

Ok, so I had to choose the second option, and make my Scrum Master live with it. But then, another problem emerged: unless you put a cleaning task for every class that has TODOs inside, sooner or later you'll end up with tasks like “Do all the TODOs in my Big-Ugly-Module”.

This will happen because doing TODOs may have very low priority, because people in a hurry don't bother doing them, and because some people don't write TODOs at all, rather thinking: “yeah, this is ugly, lets fix it, when we fix the rest of the module”.

So it seams that your code is predestined to go down the great spiral of (bio)degradation, until your team can't stand it anymore and somebody asks for a Scrum task to clean up the mess.

Is there a solution to this? Is there a third way?

Sure there is.

What if we can switch the direction the code quality goes in? What if our code can get better with time, instead of getting worse? That would be cool and it would solve our problem with TODOs in Scrum.

Boy Scout Rule

Leave every code you read in better shape than you found it.

Ha! That sounds like something everyone would sign under, and completely forget about a few minutes later, right? I mean, phrases like this sure look nice, but the real battlefield, the front-line, is a mean and messy place, right? You sit in your trench, trying to survive and keep the project alive, while bullets fly above your head. How can you try to make things better, when you couldn't keep them clean in the first place? No way to do it, man, there is too little time, right?


Let me show you how to use this rule in practice, without any significant time burden.

Real case scenario

You are in the middle of writing an application, you take a task from the Scrum white-board. It's a new feature. It says: “When importing orders, every shipping address should be verified. If it's not in our shippable zone, it should be canceled (status change + send an email to the frontend application)”.

Ok, so you want to write a new acceptance test, for this feature. But first you need to know what to test, which part of the application is responsible for importing orders. You search the project structure, and you spot the OrderService interface. You nose tells you, that it should be somewhere there. You take a look.

public interface OrderService {
     * Imports orders.

    public void importOrders();
     * Export orders.
    public void exportOrders(DateTime date);

     * Create raport of placed orders
    public OrderRaport createRaport(DateTime date);

Yeah, it's there. The importOrders() method. You search for implementations, and as you expect, there is an OrderServiceImpl.

WTF is with this blur, you ask. It's intentional. It's how much you see during your first second of looking at the code. At the first second you, as a good writer, have already noticed two things:
  1. The method has 30 lines. It's probably too long. Good method should be as short as possible. This, according to Robert C. Martin, means between 1 and 7 lines.

  2. The are several different BLOCKS of code.
What does the second thing mean? It means, that the author has noticed the first thing as well, so he decomposed the method into different blocks, by putting an empty line between them.

This is so natural, so popular, nobody thinks about it anymore. We put empty lines between different blocks of code, to help us read the code. When we read the code, we can skip such blocks, because we already know, what those blocks do.

We put together similar stuff, so we can put a name into our mind-map, that given block does something. Next, we can fast read and skip it consequently.

There are two big problems with such method:
  1. it requires you to read all the details (every line) of the code at least once, before you put names of those blocks in you mind

  2. it is not the way Object Oriented Programming is supposed to separate stuff that make a single concept

So how about fixing it, while we read it? We have to read and understand it anyway. How about not keeping the names of blocks in our memory, but putting them into the code instead.

Comment every block of code

You are doing it anyway, but instead of saving the names/explanations in your head, save them in the code for a moment.

So our code will look like this:

public void importOrders() {
//create date before importing from web service
    DateTime date = new DateTime();

//import data transfer objects from web service
    List<SalesOrderExportDetail> orders = salesOrderWS.getSalesOrdersFromWebService();

//create summary for importing orders
    SalesOrderImport salesImport = new SalesOrderImport();

//for each order try
    for(SalesOrderExportDetail salesOrder : orders) {
        try {

//convert it to domain object
            Order order = new Order();
            order.setValue(new BigDecimal(salesOrder.getValue(), new MathContext(2, RoundingMode.HALF_EVEN)));

//calculate vat
            double vat = calculator.vatRate(order.getAddress());
            BigDecimal value = calculator.value(vat);

//calculate value in PLN
            Currency curr = order.getCurrency();
            if(curr != Currencies.PLN) {
                order.setPln(converter.convert(curr, order.getValue()));

//save in repository

//prepare information whether it was succesfull                
        } catch(Exception e) {

//save the summary for importing orders

Put the comments without any indentation, so that you won't forget to get rid of them, and they won't mix with other comments in the code. Make those comments verbose, make them say everything that is important on this level of abstraction. You are a programmer, you probably write faster than you think, so there was no additional time spend on this action.
Now for the second step.

Eliminate blocks of code using explicit names

The goal is to compress all the information from inside the block and the comment into one-liner. That saves the time the reader needs to get the meaning of the code next time. It usually means, replacing the block with a method, with a name created from the comment. So for example this:
//calculate vat
    double vat = calculator.vatRate(order.getAddress());
    BigDecimal value = calculator.value(vat);

will be replaced by this:
Who said that the new method has to be in the same class? In this situation, it makes much more sense to put the use of the calculator into the order, after all it has all the data (we are using aspectj load time weaving to get the calculator into the order, but there are plenty of other methods if you don't want to use aspectj).

And this:
//convert it to domain object
    Order order = new Order();
    order.setValue(new BigDecimal(salesOrder.getValue(), new MathContext(2, RoundingMode.HALF_EVEN)));

Will be replaced by this:
Order order = orderConverter.toOrder(salesOrderDto);
Here we have decided to put the body inside a new class: OrderConverter, because the convertion is a serious responsibility and the OrderService look like it's got other things to do already (Single Responsibility Principle).

Even one-liner can be a bit fixed, for example in this part:
//create date before importing from web service
    DateTime date = new DateTime();
The comment is put, because the name of the variable does not communicate it's intention. We can get rid of the comment if we give the necessary information to the reader in other way. For example like this:
DateTime dateImportStartedAt = new DateTime();
We should eliminate every block and split every part of the code that serves a different need. Even for-each loops and try-catch expressions. For-each responsibility is to iterate over a collection, and call someone else to do the job on an element. Try-catch is responsible for handling an error, so somebody else should do the unsafe job for it.

This is the Single Responsibility Principle on a method level. Make every method have only one reason to change, and your life (and the readability of your code) will be better.

Since these are very basic and easy refactoring steps, that your IDE does automatically with little effort from you, the time burden is insignificant. You had to understand the class anyway, and on the way, you've made it better, easier to understand. Now the part of your class responsible for imports looks like this:
public void importOrders() {
    DateTime dateImportStartedAt = new DateTime();
    List<SalesOrderDto> salesOrderDtos = salesOrderWebServiceClient.getSinceLastVisitOrderedByNumber();
    ImportSummary importSummary = tryToImportEach(salesOrderDtos, dateImportStartedAt);;

private ImportSummary tryToImportEach(List<SalesOrderDto> salesOrderDtos, DateTime dateImportStartedAt) {
    ImportSummary importSummary = new ImportSummary(dateImportStartedAt);
    for(SalesOrderDto salesOrderDto : salesOrderDtos) {
    return importSummary;

private OrderImportOutcome tryToImport(SalesOrderDto salesOrderDto) {
    OrderImportOutcome orderImportOutcome = null;
    try {
        orderImportOutcome = importOne(salesOrderDto);
    } catch(Exception e) {
        orderImportOutcome = new OrderImportFailure(e);
    return orderImportOutcome;

private OrderImportSuccess importOne(SalesOrderDto salesOrderDto) {
    Order order = orderConverter.toOrder(salesOrderDto);
    return new OrderImportSuccess(order);

Every method has a meaningful name. No more than 7 lines of code per method. You don't need to divide code into blocks, methods are an object oriented solution to divide the code. By the way, you've delegated some responsibilities to other classes. You've refined the code, made it more precise, more clear, more readable.

But somewhere in your head there is a voice saying: “Hey, I had just one, 30-lines method, now I have four, taking the same space. If I do it to other methods, I'm gonna have like 15 methods per class. I'll get lost, it's no way easier for me”.

But that is, because you have one more big mistake to fix.

The name is the responsibility

Have a look at the name of the interface: OrderService. Can you tell me what this class is responsible for? Every class should have just one responsibility, what is it for OrderService?

Everything about orders?

What kind of responsibility is “everything”? There is no such thing as “everything”? Thinking this way you can create single class named God-Emperor and end your OOP right there. You'll never need other classes anymore.

No, my friend. The name SomethingService is a great mistake, just like a SomethingController or SomethingManager. I know quite a few SomethingManagers in real life, that you wouldn't be able to find any responsibilities for. They are called that way, because this is what they do: NOTHING. They just are.

But we do not speak corporation-bullshit (even though some of us work at corporations), we are Agile developers, we are writers, we name things as they are.

So our OrderService interface should be split into, let's say: OrdersImporter, OrdersExporter and OrdersReportFactory. That would make responsibilities and our intentions clear. If you do that, you end up with a WebServiceOrdersImporter implementation class, that has only 30 lines, 4 methods, only one of them public.

Now that's simple, isn't it?


It doesn't have to be expansive or difficult to make code better while you are reading it.

You shouldn't wait for the code to get really ugly. You shouldn't write TODOs only for obvious problems. Every time you have to read and understand some code, ask yourself a question: Can I make it easier? Can I make it more readable? Can I make it better?

Take at least a small step, every time you answer is yes. Good is better than good-enough. This helps turn the tide, change the (bio)degradation into positive evolution. In the end, your code gets better with time.

No one writes good code right from the start. Good code evolves from normal code, by using the Boy Scout Rule.

And if you cannot find any way to make the code better, at least eliminate blocks of code with methods. Stick to "7 lines per method", and "Single Responsibility of a method" rules.

May 9, 2010

Writer versus Constructor

What's the favorite toy from your childhood? For me, both my sisters and pretty much everyone I know that would be Lego. If you could only afford it (and in the times when I was a kid, that wasn't so easy in the post-soviet Poland), there was no greater fun, than the joy of unlimited freedom to create whatever you can only imagine. And the fact, that you had limited resources wasn't a real obstacle. It was a challenge.

Nearly all the programmers I know, fell in love with programming because of the same reason. To be able to put pure ideas to life, to create something meaningful out of nothing. Truth is, no other matter is so flexible, as the stuff we work with.

We are developers because we love to construct things that work. To give soul to the machine. To make it act on our behalf. It's like magic.

That's why it is so difficult for us to understand, that a real software craftsman is a writer, not a constructor.

Uncle Bob is talking about it at the beginning of “Clean Code”. When you are writing code, you are actually reading a lot more. How is that possible? Let's have a look at an example: you have a project going, and you take a new feature from the Scrum/Kanban wall of features. And you:
  1. read the code to find a place where putting some more code will give you the result you seek
  2. read the code to better understand the surroundings, to eliminate potential side effects of your changes
  3. write the test and the code that does what the feature is expected to do

You can start with an acceptance test first, but that only changes the order, not the fact, that the proportions of reading to writing, are always in favor of reading. Big time.

So, if reading takes so much time, how important is to make things readable?

People are working hard to learn how to write faster, how not to use mouse in their IDE, they memorize all the keyboard shortcuts, use templates and so on, but the speed up is not significant in real work. Why? Because we are only writing code 1/10 of our time. The rest is spent on reading and thinking.

A good craftsman is a good writer, because he makes the code readable, easy to grasp, easy to understand. There is a huge shift in mentality, between a constructor and a writer. Above all, the constructor's goal is to make things work. The writer's goal, on the other hand, is to make things easy to understand.

The question is, who are we writing code for? The computer? Hell no. If that was true, we would be still writing in an assembly language (or maybe even in a machine code). The whole point of procedural, functional, object oriented languages was to make it easier for us to understand the code. And that's because we don't write the code for the computer.

We write it for other programmers.

To make the shift in mentality easier, let mi show you the differences in mindsets, between the constructor and the writer.

The Constructor

The constructor is in love with technology for the sake of technology. He likes to “technologically masturbate” himself with new toys. He thinks that simplicity is for pussies, the real thing is always complex. He never removes anything, always adds more. He doesn't care that he cannot understand how his earlier solutions work, if they work why would he want to change them? He creates monsters like EJB1/2, that can do pretty much everything, but nobody is able to handle them. The he writes software to be able to use/confgure the software he has written before, because it's already too complex for anybody (maybe except for him) to understand how to use it directly.

A bigger framework is a solution to his every problem. And even if it's a new problem, he tries to modify his beloved one-to-rule-them-all tool, to be able to solve it. He is dreaming about the day, that he will have a single, big, multipurpose, futuristic wrench that works as if by magic, and does everything, from printing log files to saving the planet.

The constructor works best alone. He gets angry at people that cannot understand his programs in a second. When he works with other programmers, he is always afraid, he doesn't like others to play with his tools. When they try to do pretty much anything, they always blow something else up. Because of unforeseen side effects, a small change can devastate days of work. And it happens a lot. It gets messy, so he hates to work with others.

The Writer

The writer reads a lot, so he wants to make his code as readable, as simple as possible. He learns stuff like DSLs, patterns, eXtreme Programming, to make things easy. Easy is his keyword. He cares less about frameworks. He usually knows a few languages from different worlds, because he believes there is no single silver bullet, and different solutions are better for different problems. His code has few comments, because it doesn't need them. His code is self-documenting. His code is expressive. His code is simple, simplicity is his main value. Brilliant things are simple.

The writer always thinks about his reader. He walks hand to hand with his readers. He guides them, he cares for them. He never leaves them in the dark. His skills are in communication: he wants his intentions to be understood.

The writer works like a sniper. His changes (whether bug fixes or new features) are minimal, but the effects are exactly as expected. He never does Shotgun Surgery. He doesn't violate DRY. He is a precise man and he works with a scalpel. His code is side-effect free, simple and readable, so he knows where and how to hit. He knows what the effects will be. He keeps accidental complexity low.

The writer is agile. He doesn't set up traps, and he doesn't fall into traps. He works hard to master basic skills. He believes that without those basic skills, no framework can save him anyway.

The writer likes to work with other programmers. He is using pair programming and code reviews to make sure that his code is easy to understand by others. He wants to have another mind watching his back, and catching him when he falls. He is supportive, he is friendly. He understands that no man is an island, and that the quality of his work will be measured by the number of WTFs shouted by other developers.

A good craftsman is a good writer.

And you know what one of the most successful writers of recent times, Stephen King, says?
That he's only a craftsman.

PS: all the pictures are from Fallout games.
PS2: I've failed at giving appropriate credits to the author of the concept of programmer as a constructor. Let me fix that right away: the source of the idea that a programmer as a writer has opposition in programmer-constructor comes from a post by Andrzej Szczodrak that you can find in here