GraphQL Java 6.o

I’ve been a fan of GraphQL ever since I first tried it.  I push back against RESTful APIs to anyone that will listened (or not).  I’ve written a few post about it (GraphQL: Java Server, JavaScript Client, GraphQL: Java Schema AnnotationsGraphQL: A Java Server in Ratpack).  What I haven’t done, is stay current.  I got hooked on graphql-java at version 3.X and decided the annotations were the best way to go, and sadly the annotations development stalled and made upgrades tricky, and so I didn’t.  But it was a constant nagging itch, to upgrade, and finally I did.

This post will discuss a Ratpack server, using GraphQL-java 6.0. I should note, that as I did this work, the annotations finally release an upgrade. Doh.

GraphQL Java 6.0

I committed to upgrade. The annotations had not kept up so this meant a bit of a rewrite.  Normally I’m pretty suspicious of gratuitous annotation use.  They often mask too much of what’s really going on, and they tend to spray the information about one concern throughout your code, making it hard to locate coherent answers on a topic.  That was exactly the case here.  Leaving the annotations behind meant:

  • I had to figure out what previous magic I now had to handle on my own.
  • I had to determine just how deeply into my code they’d rooted themselves.

I tried to approach it intelligently, but in the end I went with brute force, I removed the dependency, and kept trying to build the project, ripping out references, until, while no longer working, the project built and the annotations were gone.  Then I set about fixing what I’d broken.

What Was Missing?

Basically without the annotations there were two things I needed to repair:

  • Defining the query schema
  • Wiring the queries up to the data sources

Defining Your Schema

GraphQL-java 6.0 supports a domain specific language for defining your schema known as IDL.  It’s a major win.  First, it gets your schema, which is by definition, a single concept, into one place, and makes it coherent.  Second, they didn’t go off and write “Yet Another DSL” but instead supported one that while not part of the official spec, is part of the reference implementation, and has traction in the community. Nice.

Wiring Up Your Data Sources

The best practice for this now is using the “DataFetcher” interface. The name is a bit misleading, since these aren’t just for your queries (i.e. fetching data) but also for your mutations (modifying data).  The name is weak, but the interface and it’s use is a breeze.

To the Code

I did all this work on my snippets server kata project, so for a richer example go there, but for the sake of clarity here will look at the more concise Ratpack GraphQL Server example.

The Dispatcher

This didn’t change hardly at all.  It’s still as simple as grappig a JSON map, pulling out the query and variables, and executing them:

Pretty straight forward.

Defining the Schema: IDL

So in this trivial example all I have are Company entities, defined with this bean:

And all I wanted to support was, get one, get all, save one, delete one.  So I needed to define my Company type, two queries, and two mutations. Defining this in IDL was easy:

Loading The Schema

I just tucked my schema definition into my resources folder and then:

Wiring The Data to The Schema

In GraphQL-java, the way I chose to do this is with DataFetcher implementations. So for example, to find a company, by name, from a map it would look about like:

So that’s the way to “fetch” the data, but how do you connect this to your schema? You define a “RuntimeWiring”:

And then you associate that wiring with your schema you loaded:

And Then…

Well that’s it.  You’ve:

  • Created a GraphQL dispather
  • Defined your entites
  • Defined your GraphQL schema
  • Created queries
  • Instantiated the schema, wired in the queries

Done.  Take a look at my GraphQL server in Ratpack for the complete working code.




GraphQL: A Java Server in Ratpack

[The post is out of date, please read the update]

I previously wrote about an implementation of a GraphQL server in Java.  That post is showing age because the code is part of a kata project and constantly evolves.

A Concise Example

So, I’ve created a new concise example in GitHub that exemplifies using:

The example is just the code needed to manage a list of companies in memory. It implements basic CRUD operations but with an extensible pattern.

Grab The Code

It’s all covered in ~300 lines of code:

  1. A package with a GraphQL Schema, using a Query and a Mutation class
  2. A GraphQLHandler that dispatches POST requests to GraphQL
  3. An Application that creates the Ratpack server for the GraphQLHandler

The README covers how to run it, and there are a series sample requests included.