No More Ninjas

How does a software company attract talent? Compensation? That’s how they attract people. Free lunches and foosball tables? Keep guessing.

The most effective way for a company to bag top-tier engineers is simple: let developers be developers.

Engineers Drive Innovation

Software is a symbiotic creature, and there are two ways a product is built: from the top down and the bottom up. Top-down development means that requirements are curated by and flow from the business, product owners, and managers, downward to the engineers. With the latter, developers explore new ideas and use technology that may be outside the organization’s standard gamut. Ideas for new products or features are born and pushed up to product owners where they can be cultivated.

Both of these methods must strike a balance for a company and its products to be successful. Without a focused vision, a product will fail. Without embracing new ideas and technology, a company will become irrelevant.

Open Source is King

How an organization perceives OSS is paramount to developers. Companies that contribute and maintain open source projects tend to attract talented software engineers. Just look at some of the top repositories on GitHub. Unfortunately, there can sometimes be an eternal struggle between engineers and lawyers.

It’s equally important that a company supports the use of OSS in its own products. I’ve worked on projects where the use of open source code was discouraged in favor of homegrown solutions. This is dangerously senseless considering most mature, open source projects are battle tested and have large community support.

Developers want to work at companies that embrace open source, which is a push-pull dynamic.

Let Me Work, Dammit

I do all of my development on a MacBook Pro running OSX. Some of my coworkers use similar hardware configurations with various flavors of Linux. Back when I worked with .NET, I used Windows. The CLI is now my home, however, and Vim is Old Reliable sitting in the driveway. Some prefer IntelliJ, some PyCharm, and yet others Sublime Text—to each his own.

What I’m getting at is everyone has their preferred setup for building software. If your product does not have technical constraints resulting from the stack you’re using, don’t force me out of my element. Let me use the environment I’m comfortable with because it’s the environment I’m productive with.

No More Ninjas

Tech recruiters: no more code ninjas, no more Jedis, no more rock stars, no more gurus. These words are an unfortunate by-product of the startup culture. You may have the best of intentions, but to me, these words are red flags and marginally patronizing.

Perhaps I’m overly cynical, but I tend to translate job postings of this nature as “Seeking to exploit naive, young programmer to build a startup by working unsustainable hours. You’ll get equity!” It’s the hard sell.

We get it, you’re looking for skilled programmers, but no self-respecting programmer will call him or herself a rock star. And if they do, not only does it blow expectations out of proportion, it makes them look like a dick. Let your company, its products, and its culture speak for themselves. If you aren’t finding the “rock stars” you were looking for, it wasn’t meant to be.

Let Developers Be Developers

Yes, I’m biased. Developers are opinionated—I certainly am. Nonetheless, I would hazard to guess many top tech companies tend to address several of the points I’ve touched on. Call it headstrong, obstinate, whatever, but these are things I like to get a feel for when interviewing with a company. Others may disagree, but I suspect you wouldn’t be too hard-pressed to find many who take the craft seriously share similar views.

The Art of Software

I stared at my coffee as a friend asked a mildly profound question: “what is your greatest passion in life?” Strangely, I thought of an exchange that occurred just a few months earlier while I was at the bank, opening an account for my software consulting company.

“What is the nature of your company’s business?” the banker asked.

“Building software,” my partner and I managed to respond with. Now suddenly fascinated, she looked away from her computer and at us, as if we had abruptly sprouted wings.

“Like Facebook?”

I did my best to suppress a laugh and simply nodded. I could hardly blame her. The 30-something-year-old banker’s knowledge of the domain likely consisted of the horrendous software they used at the bank, Angry Birds, and whatever insight she gleaned from watching The Social Network. About equivalent to my knowledge of banking.

I looked up from my coffee. Naturally, my answer would immediately gravitate towards software, but how to frame it in a way that made sense?

Building something that impacts people—making their lives easier, more enjoyable, or something to that effect—that’s really the goal of any engineer, but it’s an amazing ability that software developers possess. The modern-day alchemist, quite literally turning electrons into social media and flight simulators and bank transactions—things that delight or captivate; things that help us exist. We’re the janitors of data, or is it plumbers? But we’re also artists.

Software is a craft, an art, and not one that everyone is capable of doing (but certainly capable of learning). But what is art? Something that exhibits beauty in aesthetics, perhaps visually, perhaps audibly. We think of Michelangelo’s painting of the Sistine Chapel or Beethoven’s Fifth Symphony. We probably don’t think of Twitter or Facebook and certainly not the ATM you withdrew money from.

Web designers may argue that websites can be beautiful, and they’re right. Software can be both a visual and aural stimulus, but these are really just superficial observations. The same way I say “Huh, that’s pretty cool” after seeing the Sistine Chapel. Others may appreciate it more, or less.

Many would argue that the purpose of art is to evoke emotion from its audience. There’s probably a lot of truth to that, but to me, art exists on several different levels. There’s the immediate aesthetic beauty—what the eyes see and what the ears hear. There’s the emotions that it evokes from its audience—this makes me happy, this makes me sad, this makes me intrigued. And then there’s the appreciation of the craft: painters admiring a painting, not because of its obvious beauty, but because of the technical prowess it demonstrates. Software is no different.

I read something once that said software developers are never impressed. I don’t think that’s entirely true, or at least the entirety of the truth. Beyond the superficial veneer of beauty, there are the inner workings of incredibly complex systems, riddled with algorithms, design patterns, and all the things that make programmers swoon. And they run like well-oiled machines. That is art, but art that only others who share the trade can enjoy. There is elegance in code like there is elegance in the prose of a novel. The difference is in those who are able to marvel at it.

The great thing about engineering, software or otherwise, is the problem solving involved. There is no end to the amount of exceptionally difficult problems that need solving, and the way in which those problems are solved is an art in itself.

I doubt many people associate the words “art” and “software,” but there is as much creativity and craftsmanship in building software as there is engineering. It’s this drive, to build great products that affect people, that I consider my passion and my art.

Discipline in Prototyping

Writing software doesn’t require discipline, but writing good software does. I would argue that the vast majority of tech debt in projects results from PoCs/prototypes/spikes. The code from these typically aren’t intended to make it into production, but they almost invariably do in some capacity.

“I won’t bother writing unit tests for this code, it’s purely exploratory.”

The code grows…

“It’s just a rough proof-of-concept.”

…and grows…

“It won’t make it to production!”

…and grows, until pressure from above or other factors bulldoze it into a release.

This problem is not difficult to avoid, it’s entirely disciplinary. Spikes should always be timeboxed, but truthfully, this problem rarely occurs because of spikes—it happens at the onset of projects. Nearly every project gets its start as a proof-of-concept, which becomes a prototype, which becomes a product.

It’s during this process, as a project reaches its infancy, where tech debt has a tendency to accumulate like a cancerous growth. Less seasoned developers might skip out on writing unit tests or forgo code reviews because, well, it’s a prototype. This is especially tempting when you’re working in a codebase by yourself. I myself have been caught in this rut before.

I’m not saying you need to use TDD for every line of code you write (or, for that matter, at all), but, for the love of god, write unit tests around your code. If you’re writing code that’s in source control, it’s set in stone for everyone to see and, more important, maintain (and if it’s not in source control, it doesn’t exist). Write code like it will end up in production (because frankly, it probably will).

“Minimum viable product” is a popular buzzword these days but holds merit when used in the right context. What’s important to note is that an MVP is not a proof-of-concept nor a prototype. A PoC is a great way to sketch out an early draft, but an MVP is not a draft. Building something under the guise of an MVP and renouncing standard development procedures is a wildly mistaken approach.

It takes discipline. It might even take getting yourself caught in a tech-debt-riddled project before realizing just how crucial it is, but it will make you a better software developer and certainly make your projects more sustainable.

Productivity Over Process

It seems like every software company you talk to will boast about how they use the latest development process du jour—Agile, Lean, XP, Kanban—pick your poison. What’s interesting is that the people evangelizing their chosen methodology are typically managers, not developers, almost emphasizing the process more than the product. Startups and other young tech companies seem to be particularly guilty of this (after all, every time someone utters the words “lean startup”, an angel investor gets his wings).

I’ve worked on a number of different teams, mostly Agile, ranging in size from 4 to 20 developers. I’ve used everything from TFS and JIRA to Pivotal Tracker and Trello to manage stories and track bugs. A process, the way in which you produce something, is often seen as necessary by project managers and a necessary evil by developers.

Are software developers just cowboys who want to build something, guns blazing? To an extent, probably, but the conclusion that I’ve drawn is that there is no silver bullet when it comes to crafting software. It’s not one size fits all. Agile is not the be-all, end-all solution, nor is anything else.

I’ve seen teams that said they were Agile when, in fact, they weren’t in any sense of the word. To some, it’s just a buzzword used to attract talent. I’ve also worked for companies where Agile was used across all teams, no exceptions. This led to problems with the way some groups operated. It worked great for feature teams who were engaged in completing user stories, but for some of the component teams, it just didn’t make sense for the type of work they were doing. My team, very much a backend architecture group of about six developers, was merely going through the Agile motions—a bad sign indeed. We switched to a less structured Kanban process as a result because it worked for us.

Too much emphasis is placed on the process and not the productivity of a team. Am I saying that Agile is bad? Absolutely not. In most cases, an Agile team is a productive team. When an Agile team hits its stride and really grooves, the results are impeccable, but a process needs to be peripheral. It should get out of your way as fast as possible so you can get work done. Don’t just go through the motions.

How is Software Valued?

I was talking to a friend a few weeks ago who was putting together a business presentation for potential investors. He was developing a plan for a campground kiosk system that would rely on GIS data to allow guests to view and check in to camp sites. The plan was reasonable enough and mostly feasible. He carefully considered all the costs—licensing for a third-party GIS, kiosk hardware, line trenching—and then there was software.

He allocated a mere $8,000 for the kiosk software, a low-ball figure by any definition of the word, and he estimated it to take about four weeks to complete from scratch.

“Where did you get that figure?” I asked him. The answer basically boiled down to “thin air.”

I didn’t have any kind of sudden realization, but this exchange did reinforce something many others have already observed: software is remarkably undervalued.

All too often clients say something along the lines of “You want me to pay you $X per hour to sit and type on your computer?!” What’s not obvious to many is that software engineers create extraordinary value for businesses. It’s almost ironic considering just about everything these days is driven by software, to the extent that it’s almost taken for granted, and it doesn’t somehow materialize out of thin air.

So why is this the case? Is it because software isn’t a physical good? Maybe. However, I think the issue is largely attributed to the disparate levels of productivity between software engineers and other areas of industry. A developer might write an accounting system that leaves a large number of accountants redundant or automate a process that otherwise takes a dozen employees to complete. Is it fair that they are compensated accordingly? Again, it’s about creating value, but the fact is, most developers aren’t paid in proportion to the value they create or their productivity. Consultant John Cook explains why this is the case:

A salesman who sells 10x as much as his peers will be noticed, and compensated accordingly. Sales are easy to measure, and some salesmen make orders of magnitude more money than others. If a bricklayer were 10x more productive than his peers this would be obvious too, but it doesn’t happen: the best bricklayers cannot lay 10x as much brick as average bricklayers. Software output cannot be measured as easily as dollars or bricks. The best programmers do not write 10x as many lines of code and they certainly do not work 10x longer hours.

It may also be due, at least in part, to software being endlessly enigmatic to non-software people. Is this auto mechanic ripping us off on our car? Is this developer ripping us off on our point-of-sale system? It’s easy for people to see what it takes to build a bridge—designing it, performing simulated load tests, pouring the concrete, assembling the steel, laying the superstructure—these are all tangible overheads.

What does it take to build software? It’s just some bit-twiddling, right? There’s no inventory that needs to be accounted for; there’s no manufacturing labor. As developers, we know it’s a lot more involved than that. The problem with software is that it’s a living thing. After you build a home, you don’t decide to move the bathroom to the other side of the house. The same cannot be said of software.

Product owners are fickle creatures. They don’t know what they want, except that Feature X needs to be changed to Feature Y and still ship in time. I’ve been on projects where this had become so problematic that developers started leaving Feature X implemented. That way, when NPD ultimately decided X was correct in the first place, we would be on schedule, but that’s tangential to this conversation.

What I’m getting at is that there’s a lot more to building software than what may be perceived. There’s still planning, and designing, and prototyping, and implementing, and testing. But unlike the bridge or the house, the process doesn’t stop when the software ships.

No self-respecting (or sane) software engineer would agree to build a complete system in four weeks’ time for $8,000. It’s almost insulting. But to someone which software is completely foreign to—and it is to most—it might not sound so outlandish. The problem is finding the appropriate level of value. It’s easy if you’re an independent consultant, but if you’re one of several hundred developers at a company, how is your value measured? As Cook explains, output, in terms of lines of code, is not a reliable metric. In fact, one could argue it’s inversely proportional to a developer’s ability.

The romantic image of an über-programmer is someone who fires up Emacs, types like a machine gun, and delivers a flawless final product from scratch. A more accurate image would be someone who stares quietly into space for a few minutes and then says “Hmm. I think I’ve seen something like this before.”

It’s for this reason, combined with the fact that programmer salaries don’t really vary dramatically, that many developers do consulting as a profession. They know exactly what their time is worth and the value they add to a business. Coming back to the problem described earlier, the downside of consulting is that many customers don’t recognize that value. As a consultant, it’s also your job to establish what it is and why.

I took on a contract last month to build some mobile software for a small engineering firm. They needed an Android application but didn’t have the resources in-house to do it. They met with a few software shops in the area but none of them specialized in mobile development. I build Android apps. This raised my value, and I already had a pretty good idea what the app would do for their business. At that point, it’s just letting economics work itself out.

Bluetooth Blues

I spent the better part of two days working on Bluetooth connectivity for an Android app I’m developing. Going into it, I had virtually no experience working with Bluetooth, especially on Android. I quickly discovered some of the peculiarities of the platform’s Bluetooth API.

In addition to connecting to Bluetooth devices, the client wanted to pair and unpair from the app. The easy way out, and probably The Android Way™, would be to pass that responsibility off to the OS, à la an Intent:

This will bring up the Bluetooth settings menu, from which you can pair/unpair devices, but the problem is that it’s a complete context switch for the user—they are no longer in your application. I was looking to provide a more seamless experience so that the user didn’t have to leave the app at all to pair a device.

Device Discovery

The entry point for Bluetooth interaction in Android is through the BluetoothAdapter, which is used to orchestrate the device discovery process and fetch paired devices. Calling startDiscovery() will tell the adapter to start scanning for devices, and when one is found, an Intent will be fired off which can then be intercepted by a BroadcastReceiver.

The above code shows how the device discovery process is kicked off and how a BroadcastReceiver is registered to listen for discovery Intents. Note that the BroadcastReceiver is unregistered and discovery is canceled in onDestroy.

In order to react to discovery events, we must implement a BroadcastReceiver.

Device Pairing

Once you have a handle on the BluetoothDevice received in the BroadcastHandler, how do you actually pair with it? Looking at the documentation for the class, you’ll see that there are no methods for doing this. This is where things start to get a little strange.

Diving into the source code for BluetoothDevice, you’ll actually find that there is functionality for doing pairing and unpairing, but the methods are hidden from the API using the @hide annotation. What’s more interesting is that the methods are, in fact, public.

Evidently, device pairing is intended to be performed only by platform applications, which is a little curious considering the permission needed to perform pairing, android.permission.BLUETOOTH_ADMIN, is accessible by third-party applications. Nonetheless, this means we actually can pair a BluetoothDevice, just not in the way the Android engineers intended.

To access the BluetoothDevice methods needed, createBond and removeBond, we can use reflection.

The pairDevice method will prompt the user to enter a PIN for the discovered device, circumventing the need to open the Bluetooth settings. As such, the pairing does not actually complete until the correct PIN is entered. The boolean value returned from the method indicates whether the pairing process was successfully kicked off or not.

It goes without saying that this code, while functional, is volatile because these methods are technically not part of the public API, so they could change or disappear in future platform releases.

We can add an Intent filter to our BroadcastReceiver to listen for pairing events using the action BluetoothDevice.ACTION_BOND_STATE_CHANGED.

There are a few other hidden methods in BluetoothDevice, like cancelPairingUserInput, setPairingConfirmation, convertPinToBytes, and setPin, that you could potentially use to customize the pairing process or perform it programmatically, but use them at your own risk.

Once the devices are paired, they can be connected using one of BluetoothDevice’s createRfcommSocketToServiceRecord or createInsecureRfcommSocketToServiceRecord methods after determining the UUID to use, either with getUuids or fetchUuidsWithSdp (or, in most cases, using the well-known UUID 00001101-0000-1000-8000-00805F9B34FB).

It’s very likely that Android’s Bluetooth API is subject to change soon. It already has changed in some of the more recent releases, although I’m not entirely sure why Google isn’t providing a stable API for pairing. Jelly Bean 4.2 introduces a new Bluetooth stack, moving from BlueZ to a Broadcom solution, so my guess is that it’s related to this.

Implementing Spring-like Classpath Scanning in Android

One of the things that Spring 2.5 introduced back in 2007 was component scanning, a feature which removed the need for XML bean configuration and instead allowed developers to declare their beans using Java annotations. Rather than this:

We can do this:

It’s a pretty simple idea since Java makes it very easy to introspectively check a class’s annotations at runtime through its reflection API. Spring’s component scan feature also allows you to specify the base package(s) to scan for beans.

The big question is how do we get access to the classes in the classpath, specifically, those in the desired package? Java SE doesn’t provide an API for doing it, but there are ways to accomplish this. The most common (if not the only) approach is to load classes by relying on the file system. We know that we can use the ClassLoader to load a class by its package-qualified name, so it becomes a matter of retrieving the file names.

Getting the classpath itself in Java SE is easy:

This will yield something that looks like “/Users/Tyler/Workspace/Test/bin:/Users/Tyler/Workspace/Test/lib/gson-2.1.jar”. Loading the files from here is pretty straightforward, as is filtering on the package name since it maps to a directory one-to-one.

Another similar approach is to use the ClassLoader to load the resources directly:

Transition to Android

Unfortunately, these solutions don’t lend themselves to Android, which made implementing classpath scanning a little more difficult for Infinitum. The reason for this is, more or less, because of the way Android’s Dalvik VM is designed. When an Android application is compiled, the Dalvik bytecode is packaged into a file called “classes.dex” inside the APK. The good news is that the Android SDK provides an API for interacting with DEX files through the DexFile class.

In order to access classes.dex, we need a handle on the APK itself, which is actually quite easy to do:

The above code opens a DexFile for the running APK. Of course, this can have some performance implications. Opening the DexFile will potentially cause the VM to pass classes.dex through a process known as “dexopt”, which is a program that performs bytecode verification and optimization. This is an expensive process, but since we’re opening a DexFile for the APK itself, classes.dex should have already undergone this process, meaning dexopt won’t be run again.

The DexFile gives us access to the classes contained in classes.dex as an enumeration of strings representing the package-qualified class names. With this, we can iterate over the class names and load any which match the desired package.

This gets the job done, and it’s essentially how Infinitum accomplishes component scanning. However, it’s a very expensive operation. DexFile.entries() yields every class in the classpath — that is, every class in classes.dex — which includes not just application binaries, but also those of any libraries included.

It’s great that we can introspect every class in the classpath, but if we’re only interested in classes of a particular package, we’re out of luck. Every class is compiled into classes.dex and, short of decompiling it1,  there’s no way to pull out the classes we want without iterating over the entire classpath.

So, for now we settle with this somewhat inefficient solution. Nonetheless, it accomplishes what it needs to at the cost of maybe a few hundred milliseconds2, so maybe it’s not such a bad approach in the grand scheme of things.

  1. Tools for decompiling DEX files exist, such as Baksmali, but doing such a thing at runtime — if it’s even possible — would arguably not gain you any performance benefits. Still, this is something worth exploring. []
  2. On the emulator running on my MacBook Pro, the classpath scanning takes about 600 milliseconds, while on my Galaxy Nexus, it takes about 200 milliseconds. []

Introducing InfinitumFramework.com

rendering

Here’s a dose of shameless self-promotion. It’s coming up on a year since I started development on Infinitum, and I’m targeting its first full release on its birthday, February 11. Shortly before I moved the project to GitHub, they deprecated the downloads service, so I needed to fine a home for distributing the binaries as well as the Javadoc.

GitHub offers its pages service, but I figured I’d just host it myself. I threw together a website in a couple days and the result is www.infinitumframework.com. This website will be used to host the latest (and previous) releases of the framework, its documentation, and, in the future, announcements and updates for it.

Stay tuned as Infinitum approaches its first official release!

He Sed, She Sed

Shortly after switching to GitHub, I decided to relicense Infinitum from GNU LGPL to Apache License 2.0. There aren’t really any implications except one: replacing the license and copyright header in every source file.

I’m far from being a Unix expert (more like amateur at best), but I figured sed would be the quickest and easiest way to do this. Sed is a Unix utility for processing text streams, and it allows you to replace string patterns in files. A simple string replacement using sed is quite easy:

This will replace “foo” with “bar”. The “g” indicates that every matching occurrence in file.txt will be replaced, and “-i” means it will do the replacement in place.

In my case, I wanted to find every occurrence of the following string in every Java source file:

And I wanted to replace it with this:

I needed to do a multi-line replacement across a couple hundred files. Feeding lots of files to sed is actually pretty simple:

This command will pass all of the Java files in the current directory (and all sub-directories)  to sed. The reason xargs is needed is because it lets us avoid the “Argument list too long” problem.

In order to replace multiple lines, I needed to use an additional feature of sed. The “c” command lets you replace a range of lines:

There’s a caveat that I have so far ignored. Many Unix utilities have idiosyncrasies or differences between platforms, and sed is no exception. I failed to mention that I was doing this on Mac OSX, whose implementation of sed, as I encountered, had some peculiar quirks. The “-e” in the above command is one such quirk as it’s needed to perform an in-place pattern replacement on OSX.

So, I had a way to process a bunch of files at once and a way to replace multiple lines in a file. Now I just needed to combine these two techniques to replace the license header in all of my project files.

This replaces the range of lines covering the original license with the new license. It works, but the formatting becomes slightly off. That’s because OSX’s sed does not preserve leading whitespace, so the space before each asterisk is stripped. Fortunately, GNU sed does preserve leading whitespace, so building that and using it in place of OSX’s sed solved the problem. Also, GNU sed doesn’t require “-e” for in-place replacement.

Sed is a very handy little tool that every developer should have in his or her toolbelt. Admittedly, I don’t leverage Unix’s utilities nearly enough (although I’m working on it!), but tools like grep, sed, find, and xargs are immensely powerful and pretty simple to use. I think some developers have a tendency to over-engineer solutions for problems that could otherwise be solved using a trivial combination of these tools — I know I have! Of course, it’s helped that I’ve started to do all my programming, both work and play, on Mac. It’s my goal to become a better Unix developer!

Modularizing Infinitum: A Postmortem

In addition to getting the code migrated from Google Code to GitHub, one of my projects over the holidays was to modularize the Infinitum Android framework I’ve been working on for the past year.

Infinitum began as a SQLite ORM and quickly grew to include a REST ORM implementation,  REST client, logging wrapper, DI framework, AOP module, and, of course, all of the framework tools needed to support these various functionalities. It evolved as I added more and more features in a semi-haphazard way. In my defense, the code was organized. It was logical. It made sense. There was no method, but there also was no madness. Everything was in an appropriately named package. Everything was coded to an interface. There was no duplicated code. However, modularity — in terms of minimizing framework dependencies — wasn’t really in mind at the time, and the code was all in a single project.

The Wild, Wild West

The issue wasn’t how the code was organized, it was how the code was integrated. The project was cowboy coding at its finest. I was the only stakeholder, the only tester, the only developer — judge, jury, and executioner. I was building it for my own personal use after all. Consequently, there was no planning involved, unit testing was somewhere between minimal and non-existent, and what got done was at my complete discretion. Ultimately, what was completed any given day, more or less, came down to what I felt like working on.

What started as an ORM framework became a REST framework, which became a logging framework, which became an IOC framework, which became an AOP framework. All of these features, built from the ground up, were tied together through a context, which provided framework configuration data. More important, the Infinitum context stored the bean factory used for storing and retrieving bean definitions used by both the framework and the client. The different modules themselves were not tightly coupled, but they were connected to the context like feathers on a bird.

infinitum-arch

The framework began to grow large. It was only about 300KB of actual code (JARed without ProGuard compression), but it had a number of library dependencies, namely Dexmaker, Simple XML, and GSON, which is over 1MB combined in size. Since it’s an Android framework, I wanted to keep the footprint as small as possible. Additionally, it’s likely that someone wouldn’t be using all of the features in the framework. Maybe they just need the SQLite ORM, or just the REST client, or just dependency injection. The way the framework was structured, they had to take it all or none.

A Painter Looking for a Brush

I began to investigate ways to modularize it. As I illustrated, the central problem lay in the fact that the Infinitum context had knowledge of all of the different modules and was responsible for calling and configuring their APIs. If the ORM is an optional dependency, the context should not need to have knowledge of it. How can the modules be decoupled from the context?

Obviously, there is a core dependency, Infinitum Core, which consists of the framework essentials. These are things used throughout the framework in all of the modules — logging, DI1, exceptions, and miscellaneous utilities. The goal was to pull off ORM, REST, and AOP modules.

My initial approach was to try and use the decorator pattern to “decorate” the Infinitum context with additional functionality. The OrmContextDecorator would implement the ORM-specific methods, the AopContextDecorator would implement the AOP-specific methods, and so on. The problem with this was that it would still require the module-specific methods to be declared in the Infinitum context interface. Not only would they need to be stubbed out in the context implementation, a lot of module interfaces would need to be shuffled and placed in Infinitum Core  in order to satisfy the compiler. The problem remained; the context still had knowledge of all the modules.

I had another idea in mind. Maybe I could turn the Infinitum context from a single point of configuration to a hierarchical structure where each module has its own context as a “child” of the root context. The OrmContext interface could extend the InfinitumContext interface, providing ORM-specific functionality while still inheriting the core context methods. The implementation would then contain a reference to the parent context, so if it was unable to perform a certain piece of functionality, it could delegate to the parent. This could work. The Infinitum context has no notion of module X, Y, or Z, and, in effect, the control has been inverted. You could call it the Hollywood Principle — “Don’t call us, we’ll call you.”

infinitum-context-hierarchy

There’s still one remaining question: how do we identify the “child” contexts and subsequently initialize them? The solution is to maintain a module registry. This registry will keep track of the optional framework dependencies and is responsible for initializing them if they are available. We use a marker class from each module, a class we know exists if the dependency is included in the classpath, to check its availability.

Lastly, we use reflection to instantiate an instance of the module context. I used an enum to maintain a registry of Infinitum modules. I then extended the enum to add an initialize method which loads a context instance.

The modules get picked up during a post-processing step in the ContextFactory. It’s this step that also adds them as child contexts to the parent.

New modules can be added to the registry without any changes elsewhere. As long as the context has been implemented, they will be picked up and processed automatically.

Once this architecture was in place, separating the framework into different projects was simple. Now Infinitum Core can be used by itself if only dependency injection is needed, the ORM can be included if needed for SQLite, AOP included for aspect-oriented programming, and Web for the RESTful web service client and various HTTP utilities.

We Shape Our Buildings, and Afterwards, Our Buildings Shape Us

I think this solution has helped to minimize some of the complexity a bit. As with any modular design, not only is it more extensible, it’s more maintainable. Each module context is responsible for its own configuration, so this certainly helped to reduce complexity in the InfinitumContext implementation as before it was handling the initialization for the ORM, AOP, and REST pieces. It also worked out in that I made the switch to GitHub2 by setting up four discrete repositories, one for each module.

In retrospect, I would have made things a lot easier on myself if I had taken a more modular approach from the beginning. I ended up having to reengineer quite a bit, although once I had a viable solution, it actually wasn’t all that much work. I was fortunate in that I had things fairly well designed (perhaps not at a very high level, but in general) and extremely organized. It’s difficult to anticipate change, but chances are you’ll be kicking yourself if you don’t. I started the framework almost a year ago, and I never imagined it would grow to what it is today.

  1. I was originally hoping to pull out dependency injection as a separate module, but the framework relies heavily on it to wire up components. []
  2. Now that the code’s pushed to GitHub, I begin the laborious task of migrating the documentation over from Google Code. []