Connection refused for spring boot application trying to reach Mysql server - spring-boot

Question

I have a products db configured on docker:
productsdb:
container_name: productsdb
volumes:
- productsdb_data1:/var/lib/mysql
image: mysql:5.7
environment:
MYSQL_ROOT_PASSWORD: "admin"
MYSQL_PASSWORD: "admin"
networks:
- commerce_net
ports:
- "3309:3306"
When I try to connect to this db from my spring boot project, the following exception is shown during server startup:
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:na]
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490) ~[na:na]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.NativeSession.connect(NativeSession.java:144) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:956) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:826) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
... 33 common frames omitted
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.base/java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:na]
at java.base/java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:412) ~[na:na]
at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:255) ~[na:na]
at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:237) ~[na:na]
at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:na]
at java.base/java.net.Socket.connect(Socket.java:609) ~[na:na]
at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
... 36 common frames omitted
The application.properties are set to connect to host 'productsdb' as:
spring.datasource.url=jdbc:mysql://productsdb:3309/products?createDatabaseIfNotExist=true&useSSL=false
The server start was tried using docker compose as well as using the command:
docker run --network=commerce_net -p 8085:8085 producttest -d
Any possible reason why this exception could occur?

Answer 1

If you want to start your application in the same container as your database, you must use the container port instead of using the host port of your database. So the database address you use in the application should be:
spring.datasource.url=jdbc:mysql://productsdb:3306/products?createDatabaseIfNotExist=true&useSSL=false
The port definition in docker-compose.yml is made in the form of HOST:CONTAINER. That is why your first port refers to your host port, and the second one refers to your container port. You can access detailed information from the Docker documentation.

Answer 2

If springboot is also in same docker compose file then use MySQL port as 3306
If its in different docker compose file then please update your network to --network={db_compose_file_directory_name}_commerce_net and spring.datasource.url=jdbc:mysql://localhost:3309/products?createDatabaseIfNotExist=true&useSSL=false
Try to provide docker-compose file and complete docker run command for service