Sep 2, 2014

Using Spring to create a full REST API in less than 60 lines of code

Spring with Spring Data is awesome. Seriously, I've never been able to throw up a full HATEOAS REST web service this fast. To start, I'll admit my headliner lie, I'm not counting the pom.xml.

cloc .                                                                 slave-vi
       5 text files.
       5 unique files.
       2 files ignored. v 1.62  T=0.04 s (104.8 files/s, 3930.8 lines/s)
Language                     files          blank        comment           code
Maven                            1              6              7             65
Java                             3             15              0             57
SUM:                             4             21              7            122

The basics of the web service is we want to be able to create tasks, like those on a todo list, for now we want the simplest tasks possible, in as little code possible. We should use UUID's so that our service can scale horizontally, so that we can easily generate known test ID's and we know that no two entities will share an id if we ever wanted to flatten things. We need to be able to perform basic CRUD on all of our entities as well as list them.

First let's create our Task. As you can see it's incredibly simple, we have our UUID identity, the uuid and uuid2 basically are telling Hibernate and H2/PostgreSQL to use UUID's. You might ask why limit description to 100 characters, well, since these are quick tasks, I might want to share them in a tweet, and this allows enough room for a url shortner plus the description. I think the rest is pretty self explanatory.

Now let's create our Repository. Well that doesn't do anything... oh but it does, and although it doesn't show it, because this application doesn't need it, there's a nifty method signature parser dsl that allows you to build queries just by writing a method signature.

Here's our Application. ... and pom for dependencies and stuff.

Here's the output of some curl commands I ran.

For a slightly more in depth tutorial you can see the official spring date rest getting started page. In the future I'll try to write about how to actually connect to PostgreSQL and set up API Authentication and Authorization

People are always telling me how verbose Java is, how much less typing their language (especially Perl is). I'd love to see a Perl app that can do all this in fewer lines of Perl (restriction, no line may be longer than 120 characters, and must be humanly readable), I personally don't think it can be done at this time (not with full HATEOAS and as many response codes), but I'm waiting for the day it can, and can be structured this simply.

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