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Spring Boot DevTools

Faster local development with automatic restart, LiveReload, and dev-only defaults.

IntermediatePro9 min readBy Kishore BhosaleReviewed
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Why this matters

  • Slow feedback loops hide bugs — DevTools restart is a daily productivity win teams expect you to know.
  • Accidentally packaging DevTools into production images has caused real incidents.
  • Interviewers contrast DevTools restart with full context reload and with Testcontainers integration tests.

DevTools purpose

L1 · Fresher

DevTools restarts the app quickly when classpath files change and disables caches that hide template edits. It is a development-only dependency.

Restart classloaders

L2 · Intermediate

Two classloaders split stable third-party JARs from your code so restarts are faster than a cold JVM boot — still not a substitute for Testcontainers integration tests.

Production safety

L3 · Advanced

DevTools is excluded from repackaged production JARs by default. Verify your Docker build does not copy dev dependencies into the runtime image.

Remote dev (rare)

L4 · Expert

Remote DevTools tunnels exist but widen attack surface. Prefer local docker-compose with volume mounts for most teams.

Classpath scanFind @AutoConfiguration classes
@Conditional checksOnClass, OnBean, OnProperty
Register beansOnly if conditions pass
Boot checks classpath and existing beans before creating defaults.

Hook

You tweak BookController mapping for a new /api/books/search endpoint and wait thirty seconds for a full JVM restart between every save. DevTools is the first dependency to add so BookStore iteration stays in the sub-second range on Java 21.

What DevTools changes locally

Spring Boot DevTools is a development-only starter. It enables automatic restart when classpath resources change, disables template and static-resource caches, and optionally triggers LiveReload in the browser. It does not belong on the production classpath.

Add it to BookStore with Maven:

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

Gradle users apply the same developmentOnly scope so the dependency never ships in the boot JAR.

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Still to come · 6 sections

  • Restart vs full reload
  • LiveReload and static assets
  • BookStore in action
  • Runnable BookStore lab
  • Failure modes in production
  • Remote DevTools and security

Test yourself

Answer these before moving on — recall is what makes it stick.