引起：java.net.UnknownHostException：mysqldb

Question

I am working on spring boot application. I want to dockerize my spring boot application but while I'm trying to make jar file from eclipse I get error java.net.UnknownHostException . I'm a new guy in docker technology.

Here is a docker images which is stored in my docker:

Here down is my code:

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.1</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.flightbook</groupId>
    <artifactId>flight_management_system</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>flight_management_system</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

application.properties

spring.datasource.url=jdbc:mysql://mysqldb:3306/mysql_database?createDatabaseIfNotExist=true
spring.datasource.username=root
spring.datasource.password=

server.port=8040
spring.jpa.generate-ddl=true
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect

docker-compose.yml

version: "3.8"
services:
  server:
    build: .
    restart: always
    ports:
      - 8090:8090
    depends_on:
      - mysqldb
  mysqldb:
    image: "mysql:8.0"
    restart: always
    ports:
      - 3306:3306
    environment:
      MYSQL_DATABASE: mysql_database
      MYSQL_USER: root
      MYSQL_PASSWORD: 
      MYSQL_ROOT_PASSWORD:

Stack trace

Caused by: java.net.UnknownHostException: mysqldb
    at java.base/java.net.InetAddress$CachedAddresses.get(InetAddress.java:801) ~[na:na]
    at java.base/java.net.InetAddress.getAllByName0(InetAddress.java:1509) ~[na:na]
    at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1367) ~[na:na]
    at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1301) ~[na:na]
    at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:130) ~[mysql-connector-java-8.0.29.jar:8.0.29]
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63) ~[mysql-connector-java-8.0.29.jar:8.0.29]
    ... 118 common frames omitted

Answer 1

I think that the container is not actually called mysqldb , but {appname}_mysqldb , where the {appname} is the name of the parent directory, where you invoke docker-compose up .

To check if this is the case, run docker ps after starting your containers.

Answer 2

you can use in spring boot properties as database source localhost, and when you run your container use: sudo docker run --net=host -p image name