Cannot connect Spring App docker container to MySQL DB docker container - mysql

Question

I am having difficulty setting up two containers. One MySQL instance, and another a Spring Application (built with Maven) which wants to talk to the MySQL instance.
I am not sure if there is something wrong with how the ports are matching up, but I have created a network "shape-shop-network", on which both the application "shapeshop" and the database "shape-shop-db-container" should talk to each other through.
Both my "docker run" specify the correct network.
These are the steps I have taken :
create a network "shape-shop-network" for both containers.
docker network create shape-shop-network
Run MySQL container setting port to 3306, making sure to specify the "shape-shop-network"
docker run -d -p 3306:3306 --name=shape-shop-db-container --network shape-shop-network --env="MYSQL_ROOT_PASSWORD=root" --env="MYSQL_PASSWORD=root" --env="MYSQL_DATABASE=shapeshop" mysql
...followed by adding some schema and initial data :
docker exec -i shape-shop-db-container mysql -uroot -proot shapeshop < SCHEMA_AND_INIT_DATA.sql
Specify my application properties in my Spring application
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/shapeshop?useSSL=false&serverTimezone=UTC&useLegacyDatetimeCode=false
spring.jpa.database-platform=org.hibernate.dialect.MySQL8Dialect
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.platform=mysql
spring.datasource.initialization-mode=always
Do a Maven Package (to create new jar files which are put in target)
Do a Docker Build. My Docker file looks like this :
FROM openjdk:8-jdk-alpine
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]
EXPOSE 8080
The command I run is
docker build -t shapeshop:1.0 .
Then I run my image like so (on port 8080):
docker run -p 8080:8080 shapeshop:1.0 --network shape-shop-network
The exception i get is :
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_212]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_212]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_212]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_212]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.NativeSession.connect(NativeSession.java:152) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
... 103 common frames omitted
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_212]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_212]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_212]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_212]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_212]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_212]
at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65) ~[mysql-connector-java-8.0.16.jar!/:8.0.16]
Strangely I can run my application through my IDE (IntelliJ) where it connects correctly to the container.
My IDE settings look like this :