dockerized postgres and dockerized Spring boot app - spring

Question

my application.properties file
server.port=8085
spring.datasource.driverClassName=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://init-postgres:5432/dbname
spring.datasource.username=username
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.generate-ddl=true
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
and for dockerizing postgres I'm using command
docker run -d -p 5432:5432 --name init-postgres -e POSTGRES_DB=dbname -e POSTGRES_USER=username -e POSTGRES_PASSWORD=password postgres
but it gives java.net.UnknownHostException: init-postgres
I'm beginner with Docker and learning it from a tutorial. to dockerized Postgresql & Spring boot app communication.

Answer 1

If you need to dockerize both of them without docker-compose
application.config
spring.datasource.url=jdbc:postgresql://init-postgres:5432/dbname
Create network
docker network create mynet
Run postgres container with created network
docker run --net mynet --name init-postgres -d -e POSTGRES_DB=dbname -e POSTGRES_USER=username -e POSTGRES_PASSWORD=password -p 5432:5432 postgres
Create jar archive
mvn clean
mvn compile
mvn package
Create dockerfile
FROM openjdk:8-jdk-alpine
ARG JAR_FILE=target/<HERE_IS_NAME_OF_YOUR_JAR_FILE>.jar
COPY ${JAR_FILE} myapp.jar
EXPOSE 8085
ENTRYPOINT ["java","-jar" , "/myapp.jar"]
Build spring boot image myapp
docker build -t myapp .
Run spring boot container
docker run --name myapp-container --net mynet -p 8080:8080 myapp

Answer 2

If your application runs on the host without docker and your database lives inside a docker container, you need to change this line:
spring.datasource.url=jdbc:postgresql://init-postgres:5432/dbname
with
spring.datasource.url=jdbc:postgresql://localhost:5432/dbname
instead, if both the application and the database are running on docker you need to refer with the docker container name, as you stated above in the snippet you posted.
I suggest to use docker-compose, it's a handy tool that can ease the difficulties of deployment and it's useful when developing too since it allows to bring up & down your application without too much hassle. In the official docker website there is a nice introduction to the tool with examples.