Recently I changed the job. After three years (longest I ever worked for a single company) I left ThoughtWorks. Majority of my consultant career oscillated in .NET space. It was almost three years since last I was doing Java. New job … is Java (packed full of Java technologies).

I had to do some IKEA shopping one late afternoon after work (something for the house). As my journey turned out to be a waste of time (items out of stock) I was sitting in front of the IKEA building consuming a horrible £1.40 Hot Dog Menu 2. Watching the sun set I had a little epiphany! I started new job, I got dropped into source code and I was able to work without relearning Java, libraries and tools.

Then I realised that through three years of work at TW, C# and .NET changed it’s shape a lot. In a mean time Java did nothing,well … almost nothing. C# introduced new language syntax, features, influenced by dynamic and functional languages. Java had got annotations and generics (somehow weird generics).

Is that a bed thing? It gives stable platform, and more consistent syntax in legacy code. On the other hand it lacks cool features, and I do have to admit, I like new features. It’s like every time when Apple releases new iPhone instead of all cool new things on it all you get is better performance and stability

There is also the explosion of languages that run on JVM. I like Groovy and JRuby, I need to check out Clojure and Scala.

There was a lot of fear when Oracle purchased Sun. Next new release of Java will have closures. If it is caused by Oracle’s influence I hope for more to come.

It is about time for Java to make some tuff decisions and stop being 100% backwards compatible.

What you think? Comment me your thoughts.

Cheers, Greg

In one of the previous articles I wrote about the story wall that we evolved on our project. Christian in his article, described the way we worked not in pairs but in threesomes. Two developers and a QA. This was the way that involved iterative, small-steps, story delivery with constant showcasing to QA. QA was able to instantly check the correctness of a functionality, business logic, even a site layout and provide feedback to devs about it.

As any application (at least majority of them) our application has multiple points of integration to other systems. Database, web services, file system etc. One of the integration points was delivered some time ago and never tested, we were ready for a problems and bugs.

It would be very unwise to stop development because the part of the system needs fixing or some rework carried. We decided that we will shield our selfs with the layer of wrappers around third party systems , that we called Anti Corruption Layer.

The Layer gives as a constant API controlled by ourselves but it doesn’t mean that we can continue our way of working and constantly showcase all the acceptance criteria to our QAs and BAs.

We decided to bring on simulators on a board and hooking them into our anti corruption layer. This is how we achieved it:

Control

It would be very painful to switch simulator on or off using configuration in one of the file. Knowledge about the environment was not sufficient enough as we don’t want simulators to be on or off all the time. What we decided was to create a class called SimulatorDecider that will use two variables to determine if the Simulator should be on or off: current environment and a browser cookie.

The environment variable allowed us to switch simulators off regardless of the cookie, in any environment other than DEV or TEST.

Cookie in web browser is very simple to set and to remove. We created a little page called Cookie Monster that has a simple on/off buttons for setting and removing the Simulator cookie.
The approach gives a possibility to control and switch on/off different parts of the system by using different cookies for each parts.

Simulator

We have a bunch of wrappers around the integration points. The one that we are interested in, the one that we would like to simulate, we decorate with Configurable object and inject SimulatorDecider into it. This is how it works:

interface IFoo
{
  ReturnType DoStuff(ParameterType type);
}

public class Foo : IFoo
{
  public ReturnType DoStuff(ParameterType type)
  {
    // Doing some real stuff that is very important
  }
}

public class SimulatedFoo : IFoo
{
  public ReturnType DoStuff(ParameterType type)
  {
    // Doing some other stuff that is only SIMULATED
  }
}

public class ConfigurableFoo : IFoo
{
  private SimulatorDecider _simulatorDecider;

  public SimulatedFoo(SimulatorDecider simulatorDecider, IFoo realFoo, IFoo simulatedFoo)
  {
    _simulatorDecider = simulatorDecider;
  }
  public ReturnType DoStuff(ParameterType type)
  {
    if (_simulatorDecider.ShouldSimulate())
    {
      return _simulatedFoo.DoStuff(type);
    }
    return _realFoo.DoStuff(type);
  }
}

Because we are using dependency injection container (Yadic) we don’t need to worry about dependencies.
It is also possible to not code SimulatedFoo as separate type and just inline simulated behavior within the configurable type. We made this decision on a base of how complex the simulated behavior should be.

Hope you find this useful when you stuck on integration pice that you don’t know how to carry on
Comments are welcome as always

Greg

For someone like me when I was new to a code I couldn’t guess, what is the goal of that check. When you dealing with null the very important thing is to know where they came from and why it happened that null values occurred. When dealing with integration points it is even more important.

As you can guess code:

if (serverResponse == null)
{
    DoSomeStuff();
}

is not very descriptive. What actually happend when I got null, does it mean that there was a communication problem, error occurred or perhaps a null means that the operation was successful.

I think the best approach will be to avoid nulls if it is possible at all. Ways we could try to avoid it:
• use Maybe pattern
• create Empty object values
• use Null Object pattern

Maybe pattern

I’m not sure if that is it’s appropriate name but I’ve used it on few projects and it seems like people are referring to it this way.

Have a Maybe interface and return it instead of the object itself.

interface Maybe<T>
{
    bool Hasvalue;
    T Value;
}

Also have two implementation of the interface:

public class Something<T>
{
    private readonly T _value;
    public Something(T value)
    {
        _value = value;
    }

    bool HasValue { get { return true; }  }
    T Value { get { return value; } }
}

public class Nothing<T>
{
    bool HasValue { get { return false; } }
    T Value { get { throw new InvalidOperationException(); } }
}

When returning value from an object return Maybe. Collaborator that consumes value can check if it is Something or Nothing or just ask if it has value.

Empty Object value

Just like string.Empty you can implement Empty or something similar as predefined value on your type. For example:

class Hen
{
    Egg LayEgg()
    {
        // doing stuff
        return Egg.Empty;
    }
}

class Egg
{
    public static Egg Empty = new Egg(“nothing in it”);
}

You can always check before the execution if the egg is empty.

Null object pattern

Object with no default behavior. For example:

interface TV
{
void ShowMovie();
}

class LCD : TV
{
    void ShowMovie()
    {
        // showing movie
    }
}

class Plasma : TV
{
    void ShowMovie()
    {
        // showing movie
    }
}

class NullTV : TV
{
    void ShowMovie()
    {
        // do nothing
    }
}

If something is not working well and we don’t have any of the TVs available we could return NullTV and nothing will happen.
Using the patter we can validate by type if the returned TV is a valid object and act accordingly.

I’m interested what other approaches people are heaving. Also what are the approaches in dynamic languages like Python or Ruby.

Please add your comment

Greg

JSLint is a very strict JavaScript verifier. JS files corrected to a JSLint specification could be minified with confidence.

We made the decision that build should brake when JSLint detects invalid JavaScript file, so developer will need to fix it before the code checkin.

Prepare the tool base

As a first step we need to get all the tools that will execute JSLint validation against our codebase. You can grab fulljslint.js from the JSLint home page. There is no executable binary for JSLint, it is just a JavaScript file with set of rules and function to execute verification. Our working environment is Windows we can execute validation using cscript.exe command line tool that Windows has. There is a very useful script created by Jason Diamond that helps to execute JSLint validation. You can get it from from here: jslint.wsf. One last thing is a command line batch file that helps execute this tool. You can name it whatever you would like to. I named it jslint.bat. The content of it looks like this:

@cscript //nologo %~dp0\jslint.wsf %*

I put all those three files into build tree, in tools folder. You can check if all the files are valid and working properly by running this command from command line:

jslint.bat c:\path\to\your\js\file.js

Create a build target

Now that we have all the tools we can create a build target. We are using Nant as a build tool. I created Nant target and called it jslint. It looks like this.

<target name="jslint" description="validates JS files">

    <foreach item="File" property="jsfile">

        <in>

            <items>

                <include name="path\to\scripts\folder\**\*.js" />

            </items>

        </in>

        <do>

            <exec program="jslint.bat" commandline="${jsfile}" />

        </do>

    </foreach>

</target>

There is a lot of stuff that could be turned on/off during validation. If you type jslint.bat without any parameters it will give you a list of possible options. Those could as well be tweaked in the jslint.wsf file.

Hope this helps you as it did for us.

Some says that JSLint might hurt your feelings. I say, bring it on

Gregster

Where am I, ups, production, I better behave

The easiest possible way of telling the app where it is running will be in Web.config. There is already a bunch of custom setting in there, so why not just have one more. When the time comes based on the Environment information we can decide if we will still spit out single un-minified files for a development environment or serve one minified file for lightning fast production performance.

Help me, help me, Mr Helper

So, the idea with the helper is: we use it to include every single file that we need on our page. When it knows that we are on Production it will replace imports with one, plus potentially minify it and compress. So I created a class called JSHelper.

JSHelper will contain two methods, one will kind of register the file for inclusion, and the other will do the actual job. So, the C# code goes somewhat like this:

public class JSHelper
{
     private readonly IList<string> listOfFilesToInclude = new List<string>();
     public const string KEY = "JSHelper_Key";

     public void IncludeJs(string fileName)
     {
          if (!listOfFilesToInclude.Contains(fileName))
          {
                listOfFilesToInclude.Add(fileName);
          }
     }

     public string IncludeAllJs()
     {
           var scriptRoot = VirtualPathUtility.ToAbsolute("~/Scripts");
           var scriptFormat = "<script src=\"{0}/{1}\" type=\"text/javascript\"></script>\r\n";
           var importedJavaScripts = "";
           foreach (var fileName in listOfFilesToInclude)
           {
                importedJavaScripts += string.Format(scriptFormat, scriptRoot, fileName);
           }
           return importedJavaScripts;
     }
}

So, as you can see it will also eliminate potential errors of including the same JS file twice.

Now to solve next problem. The JSHelper needs to be a single instance per Web Request. It needs to be as it holds the state of all the files to be imported. Having a static means that it is shared across all web requests, not good. It has to be an instance for a every server thread. Controllers are save place for our helper to be, plus they can put stuff to a ViewData. As you might or not be aware this is accessible in aspx View template.

Take over Control

In MVC.NET there is base class for all controllers that every controller inherits. It is called Controller. Because we got some more stuff to setup in all our controller we created our own that extends base framework controller and every controller in our application extends it. This is a great place to put our JSHelper in. Code goes something like that:

public abstract class ApplicationController : Controller
{
…
     protected override void OnActionExecuting(ActionExecutingContext filterContext)
     {
          ViewData[JSHelper.KEY] = new JSHelper();
          base.OnActionExecuting(filterContext);
     }
…
}

This code will create new instance of JSHelper and put it into your ViewData for usage. Because we also extend MVC.NET base class we can have JSHelper accessible in every View we got in the application.

My VIEW of the world

So the code goes something like this:

public class BaseViewPage<TModel> : ViewPage<TModel> where TModel : class
{
    public JSHelper JSHelper
    {
        get { return (JSHelper) ViewData[JSHelper.KEY]; }
    }

}

Something similar I done for the Master Page. This way we could combine all JavaScripts into one place.

So, the example of a View with JSHelper looks like this.

Master page

…

<head>
<% JSHelper.IncludeJs("jquery.js");%>
<% JSHelper.IncludeJs("other-awesome-library.js"); %>

<asp:ContentPlaceHolder ID="headContent" runat="server" />

<%= JSHelper.IncludeAllJs() %>

</head>

<body>

…

View

…

<asp:Content ContentPlaceHolderID=”headContent” runat=”server”>

<% JSHelper.IncludeJs("blabla.js");%>
<% JSHelper.IncludeJs("hm-hm.js");%>

</asp:Content>

…

Final pieces

Now we can put into use our Web.config file and change IncludeAllJs method to serve files based on environment we are in. Not posting implementation as it could be achieved in many ways.

So, when we are serving JS on production environment we can serve one single file prepared before as a deployment task or we can dynamically prepare it by pointing web browser to another controller that will combine all the files and minified it on a flight.

You can look at some JavaScript code minification in here: http://www.crockford.com/javascript/jsmin.cs

Let me know if you find this ideas useful.

Cheerios, Greg