Docker Compose构建Maven包时PostgreSQL连接失败排查求助

构建用于Docker Compose的Maven包时出现异常，核心错误为java.net.UnknownHostException: postgres，无法解析postgres主机。本地构建Jar包无报错，但修改配置连接PostgreSQL容器后无法建立连接，相关依赖已提前添加。

异常栈信息 #

Caused by: jakarta.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to open JDBC Connection for DDL execution [The connection attempt failed.] [n/a]
        at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:431)
        at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:400)

Caused by: java.net.UnknownHostException: postgres
        at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:567)
        at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:327)
        at java.base/java.net.Socket.connect(Socket.java:751)
        at org.postgresql.core.PGStream.createSocket(PGStream.java:260)
        at org.postgresql.core.PGStream.<init>(PGStream.java:121)
        at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:140)
        at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:268)

application.properties配置 #

spring.application.name=student-app


spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://postgres:5432/student
spring.datasource.username=ABCD
spring.datasource.password=1234
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect

server.port=8090

docker-compose.yml配置 #

version: '3.7'

services:
  app:
    build: .
    ports:
      - "8090:8080"
    depends_on:
      - postgres
    networks:
      - mynetwork
      
  postgres:
    image: postgres:latest
    environment:
      POSTGRES_USER: ABCD
      POSTGRES_PASSWORD: 1234
      POSTGRES_DB: student
    ports:
      - "5433:5432"
    networks:
      - mynetwork

networks:
  mynetwork:
    driver: bridge

Dockerfile内容 #

FROM openjdk:25-slim-bullseye

ADD target/spring-postgres-docker.jar tmp/spring-postgres-docker.jar

ENTRYPOINT [ "java", "-jar" ,"tmp/spring-postgres-docker.jar" ]

已知信息 #

• 未修改配置时构建Jar包无错误
• 修改为连接PostgreSQL容器配置后无法连接，依赖已提前添加

根因排查与解决方案 #

1. depends_on未等待PostgreSQL服务就绪 #

depends_on仅保证postgres容器先于app容器启动，但不确保PostgreSQL服务完成初始化（比如数据库创建、服务监听端口就绪）。当Spring Boot应用启动时，PostgreSQL可能还在初始化流程中，导致连接失败。

解决办法：

• 在Spring Boot中配置数据库连接重试，添加以下配置到application.properties：

  spring.datasource.hikari.connection-timeout=20000
  spring.datasource.hikari.maximum-pool-size=5
  spring.datasource.test-on-borrow=true
  spring.datasource.validation-query=SELECT 1
  

• 或者在Dockerfile中集成等待脚本，等待postgres的5432端口开放后再启动应用：
  修改Dockerfile：

  FROM openjdk:25-slim-bullseye
  ADD target/spring-postgres-docker.jar tmp/spring-postgres-docker.jar
  ADD https://raw.githubusercontent.com/vishnubob/wait-for-it/master/wait-for-it.sh /wait-for-it.sh
  RUN chmod +x /wait-for-it.sh
  ENTRYPOINT ["/wait-for-it.sh", "postgres:5432", "--", "java", "-jar", "tmp/spring-postgres-docker.jar"]
  

2. 应用端口映射不匹配 #

application.properties中配置server.port=8090，但docker-compose里app的端口映射是8090:8080，容器内部应用使用8090端口，映射到宿主机8090端口应该改为8090:8090，否则外部无法访问应用，也会增加调试难度。

解决办法：
修改docker-compose.yml中app的端口配置：

ports:
  - "8090:8090"

3. 网络配置验证 #

虽然已指定自定义网络mynetwork，但需确保网络正常创建。执行以下命令检查：

docker network ls

如果mynetwork不存在，重新启动docker-compose：

docker-compose down && docker-compose up --build

内容的提问来源于stack exchange，提问作者VIGNESH REDDY