I am trying to connect MongoDb and Spring Boot in docker-compose.yml.

This is it -

version: "3.7"

services:
  app-server:
    container_name: spring
    build: .
    ports:
      - "8080:8080"
    restart: always
    depends_on:
      - db

  db:
    container_name: mongo
    image: mongo
    ports:
      - "27017:27017"
    restart: always
    volumes:
      - ./datadir:/var/lib/mongo

My Dockerfile for Spring

FROM openjdk:8-jdk-alpine
VOLUME /tmp
ARG JAR_FILE
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

POM.xml plugin to build JAR_FILE -

            <plugin>
                <groupId>com.spotify</groupId>
                <artifactId>dockerfile-maven-plugin</artifactId>
                <version>1.3.6</version>
                <executions>
                    <execution>
                        <id>build-image</id>
                        <phase>package</phase>
                        <goals>
                            <goal>build</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <repository>maximko/${project.artifactId}</repository>
                    <buildArgs>
                        <JAR_FILE>target/${project.build.finalName}.jar</JAR_FILE>
                    </buildArgs>
                </configuration>
            </plugin>

application.properties file

spring.data.mongodb.host=db
spring.data.mongodb.port=27017
spring.data.mongodb.database=HotelDB

My PROBLEM

When i run "maven package" to build my jar I get the following error.My JAR file don't creating

    com.mongodb.MongoSocketException: db
    at com.mongodb.ServerAddress.getSocketAddress(ServerAddress.java:188) ~[mongodb-driver-core-3.8.2.jar:na]
    at com.mongodb.internal.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:64) ~[mongodb-driver-core-3.8.2.jar:na]
    at com.mongodb.internal.connection.SocketStream.open(SocketStream.java:62) ~[mongodb-driver-core-3.8.2.jar:na]
    at com.mongodb.internal.connection.InternalStreamConnection.open(InternalStreamConnection.java:126) ~[mongodb-driver-core-3.8.2.jar:na]
    at com.mongodb.internal.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:117) ~[mongodb-driver-core-3.8.2.jar:na]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_181]
Caused by: java.net.UnknownHostException: db
    at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[na:1.8.0_181]
    at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928) ~[na:1.8.0_181]
    at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323) ~[na:1.8.0_181]
    at java.net.InetAddress.getAllByName0(InetAddress.java:1276) ~[na:1.8.0_181]
    at java.net.InetAddress.getAllByName(InetAddress.java:1192) ~[na:1.8.0_181]
    at java.net.InetAddress.getAllByName(InetAddress.java:1126) ~[na:1.8.0_181]
    at java.net.InetAddress.getByName(InetAddress.java:1076) ~[na:1.8.0_181]
    at com.mongodb.ServerAddress.getSocketAddress(ServerAddress.java:186) ~[mongodb-driver-core-3.8.2.jar:na]
    ... 5 common frames omitted

When i run docker-compose.yml I get the following error -

    spring        | com.mongodb.MongoSocketOpenException: Exception opening socket
    spring        |         at com.mongodb.internal.connection.SocketStream.open(SocketStream.java:67) ~[mongodb-driver-core-3.8.2.jar!/:na]
    spring        |         at com.mongodb.internal.connection.InternalStreamConnection.open(InternalStreamConnection.java:126) ~[mongodb-driver-core-3.8.2.jar!/:na]
    spring        |         at com.mongodb.internal.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:117) ~[mongodb-driver-core-3.8.2.jar!/:na]
    spring        |         at java.lang.Thread.run(Thread.java:748) [na:1.8.0_212]
    spring        | Caused by: java.net.ConnectException: Connection refused (Connection refused)
    spring        |         at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_212]
    spring        |         at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_212]
    spring        |         at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_212]
    spring        |         at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_212]
    spring        |         at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_212]
    spring        |         at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_212]

MY QUESTIONS

1) Does all these problems come from "application.properties" file, or I misconfigured something in docker-compose file?

2) Can I somehow change the host name of my mongoDB?

3) Do I need to run "mvn package" to build my App.jar file before I run "docker-compose.yml"?

Thanks for the help!

Finally... I solved my problem. This is my changes:

1)I deleted this plugin from pom.xml

        <plugin>
            <groupId>com.spotify</groupId>
            <artifactId>dockerfile-maven-plugin</artifactId>
            <version>1.3.6</version>
            <executions>
                <execution>
                    <id>build-image</id>
                    <phase>package</phase>
                    <goals>
                        <goal>build</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <repository>maximko/${project.artifactId}</repository>
                <buildArgs>
                    <JAR_FILE>target/${project.build.finalName}.jar</JAR_FILE>
                </buildArgs>
            </configuration>
        </plugin>

and replace this code in Dockerfile. In ENTRYPOINT i added mongodb connection uri to my db service(this is the main change!)

FROM openjdk:8-jdk-alpine
VOLUME /tmp
COPY target/spring-mongo-demo-0.0.1-SNAPSHOT.jar app.jar
RUN sh -c "touch /app.jar"
ENTRYPOINT ["java","-Dspring.data.mongodb.uri=mongodb://db:27017/HotelDB","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

To build my app.jar I used mavem package, but along with this you should use mavem install if your jar file was not generated

Also in application.properties file i indicated spring.data.mongodb.host=db and caught the following error

Caused by: java.net.UnknownHostException: db

To avoid this exception when building JAR file I wrote spring.data.mongodb.host=localhost instead