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docker mysql spring spring-boot

Spring Boot + MySQL + Docker Compose – Cannot make Spring Boot connect to MySQL

I’ve been trying to set up a connection between a backend (runs on Spring Boot) container and a pre-built MySQL container. However, I cannot get it to connect. My docker compose file is:

version: '3.7'
services:
test-mysql:
image: mysql
restart: always
volumes:
- db_data:/var/lib/mysql
environment:
MYSQL_DATABASE: testdb
MYSQL_USER: test
MYSQL_PASSWORD: test
MYSQL_ROOT_PASSWORD: root
backend:
depends_on:
- test-mysql
build:
context: backend
dockerfile: Dockerfile
ports:
- "8080:8080"
restart: always
volumes:
db_data: {}

my application.properties:

spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect
spring.datasource.url=jdbc:mysql://test-mysql:3306/testdb?autoReconnect=true&failOverReadOnly=false&maxReconnects=10
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=test
spring.datasource.password=test

When I use docker-compose up, Spring Boot is not able to recognize the container name test-mysql. It throws: java.net.UnknownHostException

When I change it to an IP, it says connection refused. I have been looking everywhere and couldn’t come with a fix. I hope anyone can help me out. Thank you!