How do I set up hot reload for a dockerized Spring Boot application?

I’m working on setting up an application with a React front-end and a Spring Boot back-end, alongside PgAdmin and PostgreSQL. I’ve successfully set up everything in Docker containers, including hot-reload for the front-end. However, setting up hot reload for the back-end has proven to be challenging.

I followed https://panigrahi-pratap.medium.com/spring-boot-live-reload-with-docker-db585fcca37f guide thoroughly, but still haven’t achieved my goal. Changes made to the Spring Boot code aren’t reflected in the running application within the Docker container.

Here is my setup:

Dockerfile in /backend2

# Use Maven with OpenJDK 21
FROM maven:3.9.9 AS build

# Set the working directory inside the container
WORKDIR /app

# Copy the pom.xml and the source code to the working directory
COPY pom.xml .
COPY src ./src

# Package the application (skip tests if necessary)
RUN mvn clean package -DskipTests

# Second stage: create a lightweight image for running the application
FROM eclipse-temurin:21-jdk-alpine

# Set the working directory inside the container
WORKDIR /app

# Copy the JAR file from the build stage to the runtime stage
COPY --from=build /app/target/*.jar /app/app.jar

# Expose the port the application runs on
EXPOSE 8080

# Run the Spring Boot application with DevTools enabled
ENTRYPOINT ["java", 
            "-Dspring.devtools.restart.enabled=true", 
            "-Dspring.devtools.livereload.enabled=true", 
            "-Dspring.devtools.remote.secret=mysecret", 
            "-jar", "/app/app.jar"]

application.properties in backend2

spring.application.name=backend2
spring.devtools.remote.secret=mysecret

Pom.xml in backend2:

<?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>3.3.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.albion_tooling</groupId>
    <artifactId>backend2</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>backend2</name>
    <description>backend2</description>
    <url/>
    <licenses>
        <license/>
    </licenses>
    <developers>
        <developer/>
    </developers>
    <scm>
        <connection/>
        <developerConnection/>
        <tag/>
        <url/>
    </scm>
    <properties>
        <java.version>21</java.version>
    </properties>
    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

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

</project>

docker-compose.yml

version: '3.9'

services:

  postgres:
    container_name: database
    image: postgres:16.4
    hostname: localhost
    ports:
      - "${POSTGRES_PORT}:5432"
    environment:
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      POSTGRES_DB: ${POSTGRES_DB}
    volumes:
      - albion_tooling_postgres-data:/var/lib/postgresql/data
      - ./database/docker-entrypoint-initdb.d/:/docker-entrypoint-initdb.d/
    restart: unless-stopped

  pgadmin:
    container_name: pgadmin
    image: dpage/pgadmin4
    depends_on:
      - postgres
    ports:
      - "${PGADMIN_PORT}:80"
    environment:
      PGADMIN_DEFAULT_EMAIL: ${PGADMIN_DEFAULT_EMAIL}
      PGADMIN_DEFAULT_PASSWORD: ${PGADMIN_DEFAULT_PASSWORD}
    restart: unless-stopped

  frontend:
    container_name: frontend
    build:
      context: ./frontend
      dockerfile: Dockerfile
    environment:
      CHOKIDAR_USEPOLLING: "true"
    ports:
      - "${FRONTEND_PORT}:3000"
    volumes:
      - ./frontend:/app
      - /app/node_modules
    restart: unless-stopped

  backend:
    container_name: backend
    build:
      context: ./backend2
      dockerfile: Dockerfile
    ports:
      - "${BACKEND_PORT}:8080"
    volumes:
      - ./backend2/src:/app/src
      - ./backend2/target:/app/target
      - ~/.m2:/root/.m2
    environment:
      - JAVA_OPTS=-Dspring.devtools.restart.enabled=true -Dspring.devtools.livereload.enabled=true
      - SPRING_PROFILES_ACTIVE=dev
    depends_on:
      - postgres
    restart: unless-stopped

volumes:
  albion_tooling_postgres-data: