Packaging Deployment

Why Packaging Matters

Spring Boot executable JARs eliminate WAR deployment complexity by packaging all dependencies in single runnable artifact. In production CI/CD pipelines, layered JARs optimize Docker rebuilds—separating rarely-changing dependencies (Spring Boot, libraries) from frequently-changing application code, reducing Docker push time from 5 minutes (150MB full image) to 30 seconds (5MB application layer only).

Solution: Spring Boot Maven Plugin with layered JAR configuration.

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <layers>
                    <enabled>true</enabled>  <!-- Enable layered JAR -->
                </layers>
            </configuration>
        </plugin>
    </plugins>
</build>

mvn clean package
# => Produces target/zakat-api-1.0.0.jar (executable JAR)

java -jar target/zakat-api-1.0.0.jar
# => Runs application with embedded Tomcat

Layered JAR structure:

• dependencies: External libraries (Spring Boot, PostgreSQL driver) - rarely change
• spring-boot-loader: Boot loader classes - never change
• snapshot-dependencies: SNAPSHOT dependencies - change per build (dev only)
• application: Your application code - changes frequently

Docker multi-stage build:

FROM eclipse-temurin:17-jdk as builder
WORKDIR /app
COPY target/zakat-api-1.0.0.jar app.jar
RUN java -Djarmode=layertools -jar app.jar extract

FROM eclipse-temurin:17-jre-alpine
WORKDIR /app
COPY --from=builder /app/dependencies/ ./
COPY --from=builder /app/spring-boot-loader/ ./
COPY --from=builder /app/snapshot-dependencies/ ./
COPY --from=builder /app/application/ ./
ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]

Rebuild optimization:

• Dependencies layer cached (changes rarely)
• Only application layer rebuilt (changes frequently)
• Result: 5MB push vs 150MB full image

Trade-offs: Layered JARs essential for Docker deployment. Standard executable JAR sufficient for non-container deployment.

Next Steps

• Docker Containerization - Production Docker patterns
• Embedded Servers - Server configuration