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## Compose sample application
### Java application with Spring framework and a Postgres database
Project structure:
```
.
├── backend
│ ├── Dockerfile
│ └── ...
├── db
│ └── password.txt
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├── compose.yaml
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└── README.md
```
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[_compose.yaml_ ](compose.yaml )
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```
services:
backend:
build: backend
ports:
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- 8080:8080
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db:
image: postgres
...
```
The compose file defines an application with two services `backend` and `db` .
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When deploying the application, docker compose maps port 8080 of the backend service container to port 8080 of the host as specified in the file.
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Make sure port 8080 on the host is not already being in use.
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## Deploy with docker compose
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```
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$ docker compose up -d
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Creating network "spring-postgres_default" with the default driver
Building backend
Step 1/11 : FROM maven:3.5-jdk-9 AS build
3.5-jdk-9: Pulling from library/maven
...
Successfully tagged spring-postgres_backend:latest
WARNING: Image for service backend was built because it did not already exist. To rebuild this image you must use `docker-compose build` or `docker-compose up --build` .
Creating spring-postgres_backend_1 ... done
Creating spring-postgres_db_1 ... done
```
## Expected result
Listing containers must show two containers running and the port mapping as below:
```
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
56236f640eaa postgres "docker-entrypoint.s…" 29 seconds ago Up 28 seconds 5432/tcp spring-postgres_db_1
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6e69472dc2c0 spring-postgres_backend "java -Djava.securit…" 29 seconds ago Up 28 seconds 0.0.0.0:8080->8080/tcp spring-postgres_backend_1
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```
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After the application starts, navigate to `http://localhost:8080` in your web browse or run:
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```
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$ curl localhost:8080
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<!DOCTYPE HTML>
< html >
< head >
< title > Getting Started: Serving Web Content< / title >
< meta http-equiv = "Content-Type" content = "text/html; charset=UTF-8" / >
< / head >
< body >
< p > Hello from Docker!< / p >
< / body >
```
Stop and remove the containers
```
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$ docker compose down
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Stopping spring-postgres_db_1 ... done
Stopping spring-postgres_backend_1 ... done
Removing spring-postgres_db_1 ... done
Removing spring-postgres_backend_1 ... done
Removing network spring-postgres_default
```
