Minimal Graphql Client Request with Spring Boot

Photo from Farzad Nazifi under Unsplash Licence

Introduction

Most API’s architectural styles are RESTful. For some good reasons, APIs can also be built based on a Graphql architecture style. I recently had the opportunity to call one of them. I discovered and tried several ways to perform this Graphql request, all with pros and cons. In this article, I will describe how to perform a minimal Graphql client request with Spring Boot and WebClient.

Requirements

A Spring Boot Project is mandatory. I am using maven here.

Dependencies

Mandatory

WebFlux dependency to get WebClient:

<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

Starter Test dependency:

<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-test</artifactId>
 <scope>test</scope>
</dependency>

to make sure Spring Application Context loads:

Optional

Lombok because it saves boilerplate code:

<dependency>
 <groupId>org.projectlombok</groupId>
 <artifactId>lombok</artifactId>
 <optional>true</optional>
</dependency>

Graphql Server

I found this public Countries Graphql API from trevorblades. This API uses this Countries List as data sources.

Graphql Client

Graphql request body

1. Basic curl to get familiar with Graphql client request

A Graphql request requires a body request containing at least a query. Optionally a variable and an operationName. (operationName is only required if multiple operations are present in the query. I don’t use it in this tutorial)

Just like this curl example:

curl \
--location \
--request POST 'https://countries.trevorblades.com/' \
--header 'Content-Type: application/json' \
--data-raw '{"query":"query {  \n    country(code: \"BE\") { \n       name\n       capital\n       currency\n    }\n}","variables":{}}'

You may copy/paste it into your terminal. The response should look like this:

So far we have a working Graphql curl request. Let’s now code it in java.

2. Java Graphql query

2.1 GraphqlRequestBody

Let’s create the GraphqlRequestBody object.

2.2 Graphql Query

Let’s now create a getCountryDetails.graphql file in the resources folder of the project.

query($code: ID!) {
 country(code: $code) {
   name
   capital
   currency
 }
}

2.3 Graphql Variables

Let’s create a variables.graphql file in the resources folder.

{
  “code” : “countryCode”
}

Now that I have my Graphql request body and based on what I’m expecting from the API, I create my Data Transfer Object.

Data

I create my CountryDto Object:

Eventually, let’s create the CountryClient class 😀. I said it was a minimal Graphql client request, didn’t I?

GraphqlSchemaReaderUtil class to read Graphql files stored in the resource folder.

Let’s just log the Graphql request response in the main method of our Spring Boot App.

Now, your console should log the response like this:

Graphql client Unit Test

Unit test with MockWebServer can be found here.

TL;DR

Go to Github Repo.

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