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Build and run a Spring Boot application (Maven/Gradle, JAR, and local run)

Compile, package a runnable JAR, run it, and use dev-friendly commands so you are not lost on day one of a new project.

Author: Sushil Kumar

BuildSpring BootJAR

Build and run a Spring Boot application (Maven/Gradle, JAR, and local run)

Introduction

A build compiles your .java files, runs tests (if you keep them on), and packages a fat JAR (executable with dependencies inside). A run starts the embedded Tomcat and wires your @SpringBootApplication context — the same on laptop and in many cloud images.

Real-world explanation

  • CI (GitHub Actions, Jenkins) runs the same as you: mvnw package (or gradlew build)
  • The JAR name and location is usually target/… .jar (Maven) or build/libs/… .jar (Gradle) — the log on package prints it
  • Dev runs: no need to repackage for every line change if you use the plugin to recompile in place or DevTools restart (covered in dependencies post)

Step-by-step: Maven

From the project root (where pom.xml lives):

./mvnw -q -DskipTests clean package
java -jar target/demoservice-0.0.1-SNAPSHOT.jar

Use -DskipTests only when you are certain tests are not part of the change; for day-to-day quality, let tests run in CI at least.

Run without packaging (IDE or CLI dev)

./mvnw spring-boot:run

Gradle (equivalent)

./gradlew build
java -jar build/libs/demoservice-0.0.1-SNAPSHOT.jar
 
./gradlew bootRun

Common mistakes

  • Running java -jar from the wrong directory so the JAR path is not found
  • Forgetting to set JAVA_HOME to a Java version your pom declares (e.g. 17 for Boot 3)
  • Omitting the active profile or env so the app points to H2 while you think you use Postgres (see env and profiles)

Best practices

  • Same JDK version in IDE, local shell, and CI image
  • Reproducible builds: use Wrapper scripts (mvnw, gradlew) in git
  • For local Postgres, keep docker-compose (later article) or a one-line createdb in project README your team maintains

Final summary

Package a JAR once, java -jar anywhere Java runs; spring-boot:run and bootRun are for faster day-to-day turnaround. Next: environment variables and Spring profiles for clean config per environment.