Saturday, July 30, 2016

Over engineering with CQRS pattern

I don't understand the CQRS pattern and the hype about it. Technically I believe I think I understand why people think why they want to use it.

But really? Do we really need a complete pattern of explaining that I'm writing or reading to a source? Is reading code so hard that I have to "encapsulate" the specific behavior of writing something to a database? What's wrong with update/insert?

I think we're overdoing simple things which are NOT hard and going full blown nuts with technical "solutions" which are already solved. It's incredible over engineered for something simple and its doesn't hold or solve the "benefits" of the pattern. Problem as I see it is that one is trying to create encapsulated behavior but thing is that you can't encapsulate behavior only technical things which solves it.

Do I really have to say SaveXCommand? Isn't SaveX enough? Are we that stupid that we can't figure out what SaveX means? Are the problems people working with so simple that we can only divide the in a query or a command? Really? Why stacking a http post on a command? I already KNOW it's a post! Or even more unbelievable I've seen solutions using a post and a command at the same time by including the command in the URL! What the hell?

Why stopping at creating commands or queries for a supposedly database? Shouldn't we consider writing or reading to memory a command or query? Wrap every other memory access in a command instead of simply doing an assignment? Heck you might be writing to the disk shouldn't you be writing a command for that? Hell now Samsung and Intel releasing hard drives which are 100000 faster than the current SSDs. We might ending up with a lot more closer to doing memory swapping because it's cheaper and "memory" might end up in a database.

Not only that it seems like there's a lot of different ways of implementing it since there are no real clear rules about it apparently. I've seen people trying to implement it and it always ends in with them believing the other as an complete imbecile. Why is that and why the damn effort? Making a pipeline or a "bus" instead of treating a thread or task as such and work with them instead? The cqrs pattern creates incredibly polluted code with technical details all over the code base and it smells so bad I choke on it.

Imo it's trying to solve a problem which is already solved and stop doing that.

Thursday, July 14, 2016

Are the GoF patterns dead?

I read this post on the topic on getting rid of GoF patterns. I think the author is right about that patterns are bound to a paradigm and it is so that patterns in one language might not be as "effective" in another language, even though they are in the same paradigm. I can really relate to this.

But I think patterns should be considered dead because I think people try to pick a pattern and force a solution into it, instead of solving the problem and then and only then identify the patterns, but by then one could argue that there's no need of doing that.

Also if you are working in an agile environment things change, and if you build something it will change over time, and hopefully it will change rapidly. If you invest a lot of time building things to conform to a pattern and the next iteration the first thing you have to do is to tear it down again, I'd say it's a waste of time and effort. To use the design patterns you have to understand the problem and it's quirks and when you have only a vague idea of what is needed to be done to solve the problem, "designing" with those patterns before the solution is known will set you off on the wrong course and put you in a situation where you are trying to implement a pattern and not a solution. Also even if you know the solution and how it should be done, you should solve the problem not the pattern, which is happening most of the time,

Thursday, May 5, 2016

Trouble with maven-jaxb2-plugin and Eclipse?

Does your build work with plain mvn but won't build in Eclipse (Mars.2)? Does the project fail with:

"Execution default of goal org.jvnet.jaxb2.maven2:maven-jaxb2-plugin:0.13.1:generate failed: A required class was missing while executing org.jvnet.jaxb2.maven2:maven-jaxb2-plugin:0.13.1:generate: com/sun/xml/bind/api/ErrorListener"
The reason for this is that there are two dependencies;

org.glassfish.jaxb:jaxb-xjc:jar:2.2.11

and
org.glassfish.jaxb:jaxb-runtime:jar:2.2.11


have a "malformed" parent pom. If you check the Eclipse error log it may have an error message like:

"The POM for org.glassfish.jaxb:jaxb-xjc:jar:2.2.11 is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details"
The reason for this is the following section from their shared parent; com.sun.xml.bind.mvn:jaxb-parent:pom:2.2.11 :

   <profile>
            <id>default-tools.jar</id>
            <activation>
                <file>
                    <exists>${java.home}/../lib/tools.jar</exists>
                </file>
            </activation>
            <properties>
                <tools.jar>${java.home}/../lib/tools.jar</tools.jar>
            </properties>
        </profile>
        <profile>
            <id>default-tools.jar-mac</id>
            <activation>
                <file>
                    <exists>${java.home}/../Classes/classes.jar</exists>
                </file>
            </activation>
            <properties>
                <tools.jar>${java.home}/../Classes/classes.jar</tools.jar>
            </properties>
        </profile>
        <profile>
            <id>default-rt.jar</id>
            <activation>
                <file>
                    <exists>${java.home}/../jre/lib/rt.jar</exists>
                </file>
            </activation>
            <properties>
                <rt.jar>${java.home}/../jre/lib/rt.jar</rt.jar>
            </properties>
        </profile>
        <profile>       <!--todo: remove me-->
            <id>default-rt.jar-mac</id>
            <activation>
                <file>
                    <exists>${java.home}/../Classes/classes.jar</exists>
                </file>
            </activation>
            <properties>
                <rt.jar>${java.home}/../Classes/classes.jar</rt.jar>
            </properties>
        </profile>
where the incorrect java.home variable causes those two dependencies to be not loaded so the jaxb2 plugin won't have the classes to perform schema generation.

The maven environment resolves java.home environment variable from eclipse's JAVA_HOME environment variable which, if eclipse is run with a JRE, points to a non existent library.

To fix this you need to set the JAVA_HOME Environment variable. However it seems like the authors have had their JAVA_HOME point to the <path to JDK>/bin folder so in order to reach the jre and lib folder they had to use .. to get there. However the proper way to set up JAVA_HOME is the root directory of the installation. So either way you'll break something.

To fix this in turn you have to put the following parameter in eclipse.ini after --launcher.appendVmargs:
 
-startup
plugins/org.eclipse.equinox.launcher_1.3.100.v20150511-1540.jar
--launcher.library
plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.1.300.v20150602-1417
-product
org.eclipse.epp.package.jee.product
--launcher.defaultAction
openFile
--launcher.XXMaxPermSize
256M
-showsplash
org.eclipse.platform
--launcher.XXMaxPermSize
256m
--launcher.defaultAction
openFile
--launcher.appendVmargs
-vm
<path to JDK>\bin\javaw.exe
-vmargs
-Dosgi.requiredJavaVersion=1.7
-Xms256m
-Xmx1024m

You should use the JDK runtime since it needs the tools.jar and it should be the absolute path.

To check the java_home parameter you can go to Help->About Eclipse->Installation Details button->Configuration tab and look for the java.home parameter. It should be pointing to your JDK installation.

If you only have the JDK installation on your machine you probably won't see this issue. But if you, as I have, a notorious IT department it might happen they install the JRE and your Eclipse installation will run with the JRE version instead for the JDK one. It won't help to put the tools.jar in the project since the plugins runs in a different classloader to prevent them to mix classes and versions with the project they are running in. So the plugin will still fail. Hope it helps!

Monday, April 25, 2016

Frustration

There's so much frustration in the software industry, not only that it tends to get religious about it as well. Sometimes fiercely sometimes in a sober fashion, but mostly its fierce. Sometimes its between languages and sometimes its between platforms.

I recently found myself in this situation where I changed job to a .NET shop, coming from a basically "use whatever works" (in terms of platform) to a proprietary, or more properly, constricted environment. It's working with a straight jacket and whenever you turn it tightens its grip around you until there's no other way of doing things. Not only that you are bound by the "physics" of the .NET and Windows platform, it soaks into your mind as some sort of brain wash. I'll get to that a bit later.

I started checking out C# and initially I thought "This is Java done right" and then I realized that it's even more than that. I had all these things which were really nice like LINQ, delegates even async/await which seemed like heaven initially. I finally got a language which I could use with really powerful tools without a fuss. I really thought I've found something which would make me happy and this shiny new tool would make me forget the "sorrows" of the JVM echo system.

Disappointments

I immediately started to check out frameworks to see what there was. I checked if there were ports for the most usual frameworks... and found fairly little, Not only that those I found they were not as "good" as their counterparts (YES there are good ones) there weren't much. I turned to the platform itself and found that most of the time you simply use the ones the platform had. Fair enough.

Most projects developed in this shop are developed individually by contractors which are hired whenever they are needed, and not only one person have worked on a single project. There have been several system overhauls where the code have been rewritten to suit the products, and supposedly it is in a state which would qualify as "good". Quite nervous to join such a professional shop, I eagerly dug into the code to see what I could expect and what I though would be expected of me.

I was stunned, I really couldn't believe it so I had to ask. And from one of the more senior and one of those which had worked there the longest I got this blank stare as not understanding what I were talking about. It was a freaking mess. I thought it might just that part of code I was looking at, but there were more, there were those patterns you'd expect and whatnot but all these "tools" just made it somehow worse. I can't really explain it more thoroughly but the code just were f*ked up.

Somewhat dis encouraged I started coding on my own, firmly determined to do a good job. I resorted to every tool I knew of to produce good code (and provided a solid baseline for coding in other languages). A few good frameworks like XUnit came to the rescue (damn that's a really nice framework) and I started doing quite good pace with features. Though then things started to turn ugly, most notably Dispose and the life cycle of objects. Why did they do this? It gets really ugly not only considering thread safety. Not going through all that but some of it can you read here.

Then It came to the solution part of the "ecosystem". It was just Microsoft's things. And really I do know that you can do things without it but it just sort of never gets right. You either do one thing but then you cannot do the other. And when you need help it's really hard to find out what you need to do to get things working. And there's the "easy" solution which is always the wrong one.

I do recognize that you can write good code with C#, its not that. It's the straight jacket which limits the possible solutions. And this somehow restricts the solution space of the developers. You can solve a lot of things bu using LINQ, but it's so easy to actually misuse it you don't see that you actually just did that. LINQ is a perfect example of "too much abstraction" which it seems like a viable tool to use but it really is the wrong one, though its so easy to make that decision and that's why I think the code gets so messy. There are too many tools which are easy to use so you are using it for everything, and you don't see the alternative, and suddenly its NOT the right tool anymore and suddenly you are in a dark corner with no way out.

Additional problem is that you start thinking like it as well, since you become blind for other solutions. Though I've fallen into that trap a few times myself, I feel it like its a real problem for C# developers or at least that's my experience. I don't blame the developers here, but the platform.

Quite frankly I think working with C# taught me that it's good to work with different platforms, though .NET is not the one, at least not for me. Well maybe when the Windows become Linux or any derivatives like such.




Saturday, March 21, 2015

Why TDD is good for you


I must confess, I've realized that TDD is a must have in a project. Though I don't even like TDD, right now there's no better way of developing software. Writing software is like solving a perverted salesman traveling problem where the destination keeps changing and somehow the paths you took start to make less sense as the software progress. To know if you ended up with the best solution, you'd have to build all different versions of the problem to know if that's the best way of doing it, and that's not a viable idea.

Given that you have different developers with different backgrounds you must have something they know that somebody else is producing something accordingly something they know will have the same structure and background. And you'll have to keep doing it throughout the project and if you stray off the methodology you'll end up with inconsistencies in your code. And really in a project, you don't want to spend too much time (or any) discussing technical details related to pure code.

What I don't like with TDD

One important aspect of TDD is that I think TDD gets credit for is things which is TDD cannot solve. One thing is that it somehow creates layers, and this I think is deducted from the fact that TDD help with creating better abstractions, and that is a feature which is really nice with TDD, but it's really a side effect of practicing TDD. And it's not really TDD's fault for not being able to build layers because abstractions cannot be totally abstract, because if they could, that would mean that you could send in any data (or none) and get something which is exactly the data you want, which would be an impossible thing to do. There's only one thing that could pull that off, and I doubt that it actually exist, although there are many believers out there.

Also TDD does different thing to different languages so you get more from TDD in certain languages where others benefits less of it (one could argue that those languages which needs more TDD practices are bad languages).

TDD will influence your code and therefore your solution, and this will inevitably to “test induced design damage”. This means, as Conway's law states, your code will be tainted by TDD and code written with TDD in mind will be easier to integrate in a TDD project. That also means that code which is NOT written according to TDD will be a hard to fit in a TDD project (and no it's not about framework's abilities to be integrated). That also means that trying to use TDD in a project which is not started as a TDD project, will be very hard to start using the TDD practice. Most of the time, TDD projects are not being consistent and this will hurt you in the end.

Also I think TDD is showing that your language is failing describing what you really want, and you need to rely on something external to somehow verify that you have written something which is correct accordingly to your understanding. Instead of having TDD as some sort of “document”, I'd rather have the power of have all those assertions expressed by the code. I usually consider tests which are large a code smell since they give away that the code either does too many things or the code is not expressing enough intention or is not powerful enough.

But most importantly TDD creates some sort of focus on tests and unit tests, where TDD is not about those. It's about dealing with information and always confirming to that information and the test case is about verifying this, an sort of implementation of the TDD abstraction, but also we should be able to get rid of it.

If one consider that TDD is language and tech agnostic, meaning we need TDD to have a framework to actually deliver working code, the amount of work needed to verify your code should say something about the chosen language. If the language requires a lot of test cases to verify that you did something you intended to do would mean that that language is a poor choice. I'm not going to point on specific languages here and I leave this to some future discussion.

I really hope that we one day can get rid of TDD, but as for now, there are simply no better ways to write software.

Saturday, January 3, 2015

Good separation of concerns

Separations of concerns are really important when writing software. It's tightly coupled with working and correct code and it might not be obvious at first glance. One of my personal views of this is why non typed languages are not a good choice for anything longterm, types are crucial for good separations of concerns. I've worked with typed languages in large projects and they showed that even when using types its hard to keep things separated, although its not impossible achieving good separations using a non-typed language and most of the time it just breaks down. Just the fact that you need TDD to "verify" your code is a clear indicator of this.

An example of erroneous mixing of concerns:

val print_info = function(x){
    console.log('Variable x is of type "'+typeof(x)+'" and have the value of "'+x+'");
}
var x = "123"; // Variable x is type string with value "123"

print_info(x);

x-=0; // Variable x has now type number with value 123
 
print_info(x);
Output is;
Variable x is of type "string" and have the value of "123"
Variable x is of type "number" and have the value of "123"

The above example is a really simple but important aspect on mixing concerns but most of the time these things are more subtle and not so obvious.

There are several pitfalls when designing code and knowing when you are making good decisions when building software. One good rule is the "Gun rule" which is quite simple:

A modern gun today has very good separations of concerns (although a very despicable piece of technology). Most notably you have the bullet as an example on excellent separation of concerns. You can manufacture bullets separately but still deliver functionality, there are even room for making modifications to the bullets without needing to change the gun. Obviously there are certain factors you can't change without changing the gun, such as size.

One other factor is that a gun is useless without a bullet and a bullet is equally useless without a gun, so in functionality they are tightly coupled. For the gun to work you need to deploy the bullet with the gun. And this is a good indicator how they should be deployed, they should be deployed together. If you need different release cycles for them, you should separate them into two deployments artifacts, but they should share resources. This is really facilitated by Java VM by using dynamic class loading (one really good feature but for some reason not very well understood), other technologies might have problems with this and might require a full restart.

If you now equip the gun with a scope or perhaps a laser pointer this sure makes the gun better, but it is not entirely necessary for the operation of the gun. The gun will work with and without those additions and they are good separations of concerns by themselves. These are candidates for deploying on their own.

One misconception is that just because you need a different release cycle or you have identified a module with good separation of concerns, you need to deploy it on a separate instance. With the gun as an example; having a gun in one hand and the bullet in another doesn't render it more useful or more modular, though in fact it seems like a good idea and adheres to certain architectural ideas. If this idea should be brought to an extreme you should deploy each class in a separate runtime, but that however doesn't make it more modular or better.

You should look for those things which are possible to remove, but still maintain functionality. In fact being able to remove whole blocks of functionality without impacting function is a good indicator of good separations of concerns (adding them is the same). If you have to tear something apart is an indicator its not separated enough.

There's also another thing which is overlooked with separations of concerns is that too much effort is spent on making abstractions. So much abstractions actually harms your separation of concerns, everything is so abstract you have really no idea what happens.

As an example; instead of using a specific object to be able to "tunnel" data through layers you decide yo use a map like this:
interface SomeInterface {
   public abstract void someMethod(Map<String, String> map);
}

This is convenient because you could now cut through anything just because Map and String are both in a library which happens to be global. Now you can also bunch things together, which modularly, shouldn't be together and more important there's nothing that stops you to add more things which makes no sense at all. Fortunately in Java one could do this instead:
interface SomeInterface {
   public abstract void someMethod(Object map);
}
And then cast it to the Map whenever you need that information, but um, that kind of defeats a lot of things. Not only you lose the typing you also lose the intention and the function of the data. And when you loose that information, you also lose separations of concerns because now you don't know where you separations starts and where they ends.

Thursday, December 11, 2014

My thoughts on the HATEOAS debate

So HATEOAS is a hot topic. The discussions is about whether if its a good way of actually using it for an API or it should be the API. There are several things that concerns me.

Firstly there's no programming model for HATEOAS, such a like functional programming, procedural or like SQL type. Its representing something which there are no other mechanics for, so why would it be suitable for APIs?

Secondly the so called APIs, with exposing resources, requires a client which is dynamic enough to actually understand all of that data, and simple links to describe their relations. I haven't yet seen a language which does this natively so why would HATEOAS do this? SQL is pretty good at expressing relations and linking it together, however it doesn't understand what it is. Why would HATEOAS be so much better?

If HATEOAS is all of what you need to describe an API, why do I need a network to make use of it. Why isn't there a way of using it like a language? When there's a way of coding it and expression it as logical relations, I'd say it's something worth looking at.

I think all of those who think they need HATEOAS to describe an API have no idea of how to make one, it's simple like that. Yes you can create something which resembles an API, because you are exposing something which an consumer could use for something. BUT that's still not an API, simply because an API is so much more than how you relate resources to each other.

Most of the time when I see arguments for HATEOAS is the ability to extend without changing the client. The problems with having to change code because you update your API is a technical problem, not a API problem.

If there's any out there which could present me with a HATEOAS client which doesn't contain any code at all (!) and is able to understand what it can do with the API the client is exposed to and does everything the API exposes in a comprehensive matter which is useful, then I'd start think HATEOAS is a good thing.

Thing is, if you cannot show that you don't need a client which you have to translate the resources into something useful, HATEOAS is just another way for hipsters to mess up APIs.

Some links to read more about it: Jeff KnuppMule Soft,API Evangelist