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An Example of Overengineering: Keep it WET

April 28, 2021

Author(s)

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    Nicolas Frankel

    Nicolas is a developer advocate with 15+ years experience consulting for many different customers, in a wide range of contexts (such as telecoms, banking, insurances, large retail and public sector). ... Learn more

This week's post is pretty short. I've already written about overengineering, but this adds a personal touch.

I had to rewrite my Jet Train demo to use another data provider, switching from a Swiss one to a Bay Area one. One of the main components of the demo is a streaming pipeline.

The pipeline:

  1. Reads data from a web endpoint
  2. Transforms data through several steps
  3. Writes the final data into an in-memory data grid

Most of the transform steps in #2 enrich the data. Each of them requires an implementation of a BiFunction.

These implementations all follow the same pattern:

  • We evaluate the second parameter of the BiFunction.
  • If it is null, we return the first parameter;
  • if not, we use the second parameter to enrich the first parameter with and return the result.

It looks like this snippet:

fun enrich(json: JsonObject, data: String?): JsonObject =
  if (data == null) json
  else JsonObject(json).add("data", data)

In the parlance of Object-Oriented Programming, this looks like the poster child for the Template Method pattern. In Functional Programming, this is plain function composition. We can move the null-check inside a shared function outside of the bi-function.

fun unsafeEnrich(json: JsonObject, data: String?): JsonObject =
    JsonObject(json).add("data", data)                                         // 1

fun <T, U> nullSafe(f: BiFunction<T, U?, T>): BiFunction<T, U?, T> =           // 2
    BiFunction<T, U?, T> { t: T, u: U? ->
        if (u == null) t
        else f.apply(t, u)
    }

val unsafeEnrich = BiFunction<JsonObject, String?, JsonObject> { json, data -> // 3
  unsafeEnrich(json, data)
}

val safeEnrich = nullSafe(unsafeEnrich)                                        // 4
  1. Move the null-check out of the function
  2. Factor the null-check into a BiFunction
  3. Create a BiFunction variable from the function
  4. Wrap the non null-safe BiFunction into the safe one

We can now test:

println(safeEnrich.apply(orig, null))
println(safeEnrich.apply(orig, "x"))

It works:

{"foo":"bar"}
{"foo":"bar","data":"x"}

When I finished the code, I looked at the code and thought about the quote from Jurassic Park:

Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.

I'm no scientist, but I felt it applied to the work I just did. I realized that I refactored in order to comply to the DRY principle. When looking at the code, it didn't look more readable and the code added to every function was minimal anyway. I threw away my refactoring work in favor of the WET principle.

There are two lessons here:

  1. Think before you code - this one I regularly forget.
  2. Don't be afraid to throw away your code.

Originally published at A Java Geek on April 14th, 2021

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Author(s)

  • Avatar photo
    Nicolas Frankel

    Nicolas is a developer advocate with 15+ years experience consulting for many different customers, in a wide range of contexts (such as telecoms, banking, insurances, large retail and public sector). ... Learn more

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