docker compose error "Connection to localhost:5432 refused." - postgresql

Question

When I run my docker-compose, I face this error:
Error message
app | 2021-09-23 11:52:51.860 ERROR 1 --- [ main] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Exception during pool initialization.
app |
app | org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
app | at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:280) ~[postgresql-42.2.5.jar!/:42.2.5]
app | at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) ~[postgresql-42.2.5.jar!/:42.2.5]
app | at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195) ~[postgresql-42.2.5.jar!/:42.2.5]
I tried to change the url in my application.properties file and the error is the same.
This is my application.properties file:
application.properties
spring.datasource.url=jdbc:postgresql://postgres:5432/employees
spring.datasource.username=postgres
spring.datasource.password=root
spring.jpa.show-sql=true
server.port=8086
## Hibernate Properties
# The SQL dialect makes Hibernate generate better SQL for the chosen database
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true
# Hibernate ddl auto (create, create-drop, validate, update)
spring.jpa.hibernate.ddl-auto = update
`
This is my Dockerfile:
Dockerfile
from openjdk:8
copy ./target/springboot2-postgresql-jpa-hibernate-crud-example-0.0.1-SNAPSHOT.jar employee-jdbc-0.0.1-SNAPSHOT.jar
CMD ["java","-jar","employee-jdbc-0.0.1-SNAPSHOT.jar"]
And this is my docker-compose:
docker-compose
version: "3"
services:
postgres:
image: postgres:latest
network_mode: bridge
container_name: postgres
volumes:
- postgres-data:/var/lib/postgresql/data
expose:
- 5430
ports:
- 5430:5430
environment:
- POSTGRES_PASSWORD=root
- POSTGRES_USER=postgres
- POSTGRES_DB=employees
# APP*****************************************
app:
image: app
network_mode: bridge
container_name: app
expose:
- 8081
ports:
- 8081:8081
depends_on:
- postgres
links:
- postgres
environment:
- POSTGRES_PASSWORD=root
- POSTGRES_USER=postgres
- POSTGRES_DB=employees
- POSTGRES_URL=jdbc:postgresql://postgres:5432/employees
volumes:
postgres-data:

Answer 1

Can you run this command to check
sudo lsof -n -u postgres |grep LISTEN or sudo netstat -ltnp | grep postgres
should show the TCP/IP addresses and ports PostgreSQL is listening on
It can be postgres is already running and your image is not running using docker. Maybe killing the process will help you if it is already running.