updates Dockerfile with Spring Boot best practices

Author: tjuerge

Dockerfile

@@ -1,13 +1,31 @@
-FROM eclipse-temurin:11-jre-focal
+# Build stage
+FROM eclipse-temurin:17-jdk-jammy AS builder
+WORKDIR /build
 
+# Copy maven wrapper and pom.xml first for better layer caching
+COPY .mvn/ .mvn/
+COPY mvnw pom.xml ./
+RUN ./mvnw dependency:go-offline
+
+# Copy source and build
+COPY src ./src
+RUN ./mvnw clean package -DskipTests
+
+# Extract layers for better caching
+RUN java -Djarmode=layertools -jar target/*.jar extract
+
+# Runtime stage
+FROM eclipse-temurin:17-jre-jammy
 WORKDIR /app
 
 # Add a non-root user to run the application
 RUN groupadd -r spring && useradd -r -g spring spring
 
-# Copy the JAR file
-ARG JAR_FILE=target/*.jar
-COPY ${JAR_FILE} app.jar
+# Copy layers from build stage
+COPY --from=builder /build/dependencies/ ./
+COPY --from=builder /build/spring-boot-loader/ ./
+COPY --from=builder /build/snapshot-dependencies/ ./
+COPY --from=builder /build/application/ ./
 
 # Set ownership of the application files
 RUN chown -R spring:spring /app
@@ -21,5 +39,8 @@ ENV JAVA_OPTS="-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0"
 # Expose the application port
 EXPOSE 8080
 
+# Add health check
+HEALTHCHECK --interval=30s --timeout=3s CMD curl -f http://localhost:8080/actuator/health || exit 1
+
 # Set the entry point
-ENTRYPOINT ["sh", "-c", "java ${JAVA_OPTS} -jar app.jar"]
+ENTRYPOINT ["sh", "-c", "java ${JAVA_OPTS} org.springframework.boot.loader.JarLauncher"]