ExtJS 5 and Gradle – Playing Together

ExtJS is pretty nice, overall, and it comes with a powerful build tool – Sencha Cmd.

Running builds with it can be tedious, because it doesn’t have any up-to-date checks – it constantly rebuilds stuff it doesn’t need. Oh, the time wasting!

As it turns out, Sencha Cmd is an Ant-based build tool. Which means we can create Gradle builds that augment it – given us support for such things as up-to-date checks.

Like this:

Share and Enjoy!

Object equality is context sensitive

Equality is context sensitive. It’s very rarely as cut-and-dried as people think it is.

As a simple example, consider two $5 notes. I think everyone can agree that these notes have the same value – they are both worth $5. But are they equal?

Continue reading

Immutable objects the lazy way

Building properly immutable objects in Java can be annoying, especially if they’ve got a bunch of properties – too many to put into a readable constructor.1

You can implement the Builder pattern, but a lot of the time that just feels like overkill. But you don’t want to put in a bunch of setter methods, because that’s just asking for trouble. So what do you do?

Continue reading

Java, Equality, Mutability

TL;DR version: Don’t implement equals() on mutable objects.

This is a post I’ve been tossing around for a couple of years, ever since a lunchtime debate with a colleague. It’s a simple statement: You shouldn’t implement the equals() method if your object isn’t immutable.1

Continue reading

Example Hadoop Job that reads a cache file loaded from S3

I had all sorts of problems getting my head around how cache files work with Hadoop. Finally, I stumbled across the answer – when you add a cache file (see HadoopMain#48), it’s available to read as a local file inside the mapper (MyMapper#36).

When running in Elastic MapReduce, the file URI can be an S3 file, using either s3://bucket/path or s3n://bucket/path – this may or may not work in other Hadoop implementations, but the general approach would work fine.

See the gist at https://gist.github.com/twasink/8813628

How-To: Grails, GORM and SimpleDB

I went to build a new Grails-based app today, and I wanted to use SimpleDB as a backend (the app is an internal-use administration app, to configure a suite of AWS-deployed apps). So I went looking on how to use GORM with SimpleDB. This turned out to be a non-trivial task, so I thought I’d share the process with everyone.

Continue reading