Examples

The repository contains two runnable Spring Boot applications that expose the same REST API:

Project	Web stack	Kuery Client API
spring-data-r2dbc	Spring WebFlux + coroutines	KueryClient
spring-data-jdbc	Spring WebMVC	KueryBlockingClient

Both demonstrate dynamic SQL, collection binding, generated values, custom converters, programmatic and declarative transactions, and Micrometer Observation with Prometheus.

Prerequisites

• Java 17 or later
• Docker with the Compose plugin
• A clone of the Kuery Client repository

The examples use the repository source through Gradle composite builds, so you do not need to publish artifacts locally.

Start MySQL

From the repository root:

cd examples
docker compose up -d
./init_mysql.sh

This starts MySQL 8.0.37 on localhost:13306; the initialization script waits for it to accept connections, creates the testdb database, and inserts sample users and orders. The script is not idempotent, so run it once for a newly created container.

Run an application

Continue from the examples directory. Run one application at a time because both listen on port 8080:

R2DBC

../gradlew :spring-data-r2dbc:bootRun

JDBC

../gradlew :spring-data-jdbc:bootRun

Wait until Spring Boot reports that the application has started, then try the API from another terminal.

Try the API

# List the two seeded users
curl http://localhost:8080/users

# Fetch one user
curl http://localhost:8080/users/1

# Exercise collection binding with an IN clause
curl 'http://localhost:8080/users?usernames=user1&usernames=user2'

# Fetch a mapped join result
curl http://localhost:8080/users/1/orders

# Inspect Kuery Client metrics
curl http://localhost:8080/actuator/prometheus | grep kuery_client

The list request returns data shaped like:

[
  {"userId":1,"username":"user1","email":"user1@example.com"},
  {"userId":2,"username":"user2","email":"user2@example.com"}
]

Read the matching ExampleApplication.kt to compare the R2DBC and JDBC implementations:

• R2DBC application
• JDBC application

Stop and reset

Stop the application with Ctrl+C, then remove the example container and its data:

docker compose down

Run the start and initialization steps again to get a clean database.