Java Springboot application returning password authentication failed for user "postgres"

I was getting this when running my application locally and did not manually create my db, user and password. After manually creating them and then rerunning the application worked.

I solved it, in my case, I needed to connect to PostgreSQL, and I had it running in Docker. The first step was to check if port 5432 was in use with the command: netstat -a which it was. The problem was that I also had PostgreSQL installed locally, and it had port 5432 open, so I stopped the process from Windows -> Services. That worked for me.

I had the same problem.

In my case I was attempting to connect to a Postgres docker container which I had mapped to port 5432 on my local machine. What I didn't realise was that I also had PostgreSQL Server installed locally on my machine, and running on that same port.

Go into the Services app if using Windows and check if PostgreSQL Server is running. If it is, stop the service and try run your application again.

in my case it was necessary to restart docker-compose one time after that the spring boot application connected to postgresql server without any issue.

docker-compose.yml:

volumes:
    pg-data:
    gradle-cache:

  services:
    db:
      image: postgres:14.8-alpine
      container_name: db
    volumes:
      - pg-data:/var/lib/postgresql/data
      - ./etc/postgres/initdb:/docker-entrypoint-initdb.d
    expose:
      - 5432
    ports:
      - "5432:5432"
    environment:
      - POSTGRES_PASSWORD=$SPRING_DATASOURCE_PASSWORD
      - PGDATA=/var/lib/postgresql/data/pg-data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 10s
      timeout: 5s
      retries: 5
    restart: always

  builder:
    image: gradle:8.11.1-jdk17-jammy
    container_name: builder
    working_dir: /app
    volumes:
      - .:/app
      - gradle-cache:/root/.gradle
    command: gradle bootJar --stacktrace

  app:
    image: openjdk:17-jdk-slimthe app
    container_name: app
    working_dir: /app
    volumes:
      - .:/app
    expose:
      - 8080
    ports:
      - "8080:8080"
    command: java -jar build/libs/app.jar
    restart: on-failure
    depends_on:
      builder:
        condition: service_completed_successfully
      db:
        condition: service_healthy

init.sql:

CREATE TABLE IF NOT EXISTS person (
    id SERIAL PRIMARY KEY,
    first_name VARCHAR(128) NOT NULL,
    last_name VARCHAR(200) NOT NULL
);

.env:

DB_NAME=postgres
DB_HOST=db
SPRING_DATASOURCE_PASSWORD=<changeme>
SPRING_DATASOURCE_USERNAME=postgres
SPRING_DATASOURCE_URL=jdbc:postgresql://$DB_HOST:5432/$DB_NAME