Docker Compose中SpringBoot服务无法连接MySQL容器求助

问题场景 #

单独运行MySQL Docker镜像，本地启动SpringBoot服务可正常连接；但通过Docker Compose同时启动两者时，连接被拒绝，已尝试自定义网络等方案，耗时2天仍未解决。

现有配置 #

Docker Compose配置 #

version : '3.8'
services:
  healthcare:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8080:8080"
    depends_on:
      - mysql
    restart: always
    environment:
      RDS_URL: mysql
    networks:
      - saman-network
    
  mysql:
    image: mysql:8-oracle
    container_name: mysql
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: hospital_db
      MYSQL_USER: saman
      MYSQL_PASSWORD: saman
    volumes:
      - myvolume:/var/lib/mysql
    ports:
      - "3308:3306"
    networks:
      - saman-network
volumes:
  myvolume:
  
networks:
  saman-network:

application.properties配置 #

server.port=8080
spring.application.name=healthcare
spring.datasource.url=jdbc:mysql://${RDS_URL:localhost}:3308/hospital_db
spring.datasource.username=saman
spring.datasource.password=saman
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQLDialect
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

错误信息 #

springboot-hospitalmng-sample-healthcare-1  |   ... 46 common frames omitted
springboot-hospitalmng-sample-healthcare-1  | Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

springboot-hospitalmng-sample-healthcare-1  |   ... 59 common frames omitted
springboot-hospitalmng-sample-healthcare-1  | Caused by: java.net.ConnectException: Connection refused
springboot-hospitalmng-sample-healthcare-1  |   at java.base/sun.nio.ch.Net.pollConnect(Native Method) ~[na:na]
springboot-hospitalmng-sample-healthcare-1  |   at java.base/sun.nio.ch.Net.pollConnectNow(Net.java:672) ~[na:na]
springboot-hospitalmng-sample-healthcare-1  |   at java.base/sun.nio.ch.NioSocketImpl.timedFinishConnect(NioSocketImpl.java:542) ~[na:an]

springboot-hospitalmng-sample-healthcare-1  | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
springboot-hospitalmng-sample-healthcare-1  | 2023-01-05T14:20:37.165Z ERROR 1 --- [           main] j.LocalContainerEntityManagerFactoryBean : Failed to initialize JPA EntityManagerFactory: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to open JDBC Connection for DDL execution

问题原因及解决方案 #

1. 数据库端口错误 #

容器间通信使用容器内部端口，而非映射到主机的端口。你的MySQL容器内部端口是3306，主机映射端口是3308，但SpringBoot容器连接时用了3308，导致无法访问。

修改application.properties中的数据库URL：

spring.datasource.url=jdbc:mysql://${RDS_URL:localhost}:3306/hospital_db

2. MySQL未完全就绪时SpringBoot已启动 #

depends_on仅保证容器启动顺序，不保证MySQL服务已完全初始化。需要添加健康检查，让SpringBoot等待MySQL就绪后再启动。

修改Docker Compose配置：

version : '3.8'
services:
  healthcare:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8080:8080"
    depends_on:
      mysql:
        condition: service_healthy  # 等待MySQL健康检查通过
    restart: always
    environment:
      RDS_URL: mysql
    networks:
      - saman-network
    
  mysql:
    image: mysql:8-oracle
    container_name: mysql
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: hospital_db
      MYSQL_USER: saman
      MYSQL_PASSWORD: saman
    volumes:
      - myvolume:/var/lib/mysql
    ports:
      - "3308:3306"
    networks:
      - saman-network
    healthcheck:  # 添加健康检查
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "saman", "-psaman"]
      interval: 5s
      timeout: 5s
      retries: 10
volumes:
  myvolume:
  
networks:
  saman-network:

验证修改 #

执行docker-compose down清理现有容器，再执行docker-compose up --build重新构建启动。此时SpringBoot会等待MySQL服务完全就绪后再尝试连接，端口也符合容器间通信要求，即可正常建立连接。

内容的提问来源于stack exchange，提问作者Saman KHATAEI