gradle-spring-boot-integration

Works with build.gradle.kts, application.yml, and Dockerfile configurations.

Gradle Spring Boot Integration

Purpose
When to Use
Quick Start
Instructions
Examples
Commands Reference
Troubleshooting
See Also

Purpose

Set up and configure Spring Boot projects in Gradle with proper JAR creation, Docker optimization, and multi-module support. This skill covers bootable JAR setup, layered JARs for optimal Docker caching, and Spring Boot-specific task configuration.

When to Use

Use this skill when you need to:

Set up new Spring Boot projects with Gradle
Create executable JAR files for Spring Boot applications
Configure layered JARs for optimized Docker builds
Set up multi-module projects with shared libraries
Configure Spring Boot DevTools for hot reload
Inject build information into application.yml
Set up Spring Boot Actuator for monitoring
Configure testing with Spring Boot test starters

Quick Start

Minimal Spring Boot setup in build.gradle.kts:

plugins {
    id("java")
    id("org.springframework.boot") version "3.5.5"
    id("io.spring.dependency-management") version "1.1.7"
}

group = "com.example"
version = "0.0.1-SNAPSHOT"

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(21)
    }
}

repositories {
    mavenCentral()
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-web")
    testImplementation("org.springframework.boot:spring-boot-starter-test")
}

tasks.test {
    useJUnitPlatform()
}

Run and build:

./gradlew bootRun                                    # Run locally
./gradlew bootJar                                    # Create executable JAR
./gradlew bootRun --args='--spring.profiles.active=dev'  # Run with profile

Instructions

Step 1: Apply Spring Boot Plugin

Configure the Spring Boot Gradle plugin for your project type:

// build.gradle.kts - Web Service (creates bootable JAR)
plugins {
    id("java")
    id("org.springframework.boot") version "3.5.5"
    id("io.spring.dependency-management") version "1.1.7"
}

Key plugins:

org.springframework.boot: Creates executable JARs, provides bootRun task
io.spring.dependency-management: Automatically imports Spring Boot BOM

Step 2: Configure Java Toolchain

Specify Java version for consistency:

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(21)
    }
}

Step 3: Add Spring Boot Dependencies

Use the BOM automatically imported by the plugin:

dependencies {
    // Spring Boot starter (no version needed - from BOM)
    implementation("org.springframework.boot:spring-boot-starter-web")
    implementation("org.springframework.boot:spring-boot-starter-actuator")
    implementation("org.springframework.boot:spring-boot-starter-data-jpa")

    // Development only (DevTools for hot reload)
    developmentOnly("org.springframework.boot:spring-boot-devtools")

    // Test dependencies
    testImplementation("org.springframework.boot:spring-boot-starter-test")
}

// Enable JUnit 5
tasks.test {
    useJUnitPlatform()
}

Step 4: Configure Bootable JAR Creation

For services (executable JARs):

tasks.bootJar {
    enabled = true
    archiveClassifier = ""  // No classifier for main artifact
}

tasks.jar {
    enabled = false  // Disable plain JAR
}

For libraries (plain JARs):

tasks.bootJar {
    enabled = false  // Not executable
}

tasks.jar {
    enabled = true  // Create library JAR
}

Step 5: Enable Layered JARs for Docker Optimization

Layered JARs separate dependencies by change frequency for better Docker caching:

tasks.bootJar {
    enabled = true

    layered {
        enabled = true
        application {
            enabled = true
        }
        dependencies {
            enabled = true
        }
        springBootLoader {
            enabled = true
        }
        snapshot {
            enabled = true
        }
    }
}

Layers (in order):

dependencies: Rarely-changing external dependencies
spring-boot-loader: Spring Boot loader classes
snapshot-dependencies: Snapshot/SNAPSHOT versions (changing)
application: Application classes (most frequently changing)

Extract layers in Dockerfile:

FROM eclipse-temurin:21-jre-alpine AS builder
WORKDIR /builder
COPY build/libs/app.jar .
RUN java -Djarmode=layertools -jar app.jar extract

FROM eclipse-temurin:21-jre-alpine
WORKDIR /app
COPY --from=builder /builder/dependencies ./
COPY --from=builder /builder/spring-boot-loader ./
COPY --from=builder /builder/snapshot-dependencies ./
COPY --from=builder /builder/application ./
ENTRYPOINT ["java", "org.springframework.boot.loader.launch.JarLauncher"]

Step 6: Configure Application Properties

Inject build information into application.yml:

tasks.processResources {
    filesMatching("application.yml") {
        expand(
            "version" to project.version,
            "name" to project.name,
            "timestamp" to System.currentTimeMillis()
        )
    }
}

In application.yml:

spring:
  application:
    name: ${name}

info:
  app:
    name: ${name}
    version: ${version}
    build-timestamp: ${timestamp}

Step 7: Set Up Spring Boot DevTools for Local Development

Enable hot reload during development:

dependencies {
    developmentOnly("org.springframework.boot:spring-boot-devtools")
}

Trigger reload:

IntelliJ: Build Project (Cmd/Ctrl + F9)
Eclipse: Save file
CLI: Run ./gradlew compileJava in separate terminal

Step 8: Configure Actuator for Monitoring

Add actuator endpoints and metrics:

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-actuator")
    implementation("io.micrometer:micrometer-registry-prometheus")
}

In application.yml:

management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus,metrics,env
  metrics:
    export:
      prometheus:
        enabled: true
  endpoint:
    health:
      show-details: always

Examples

Example 1: Simple Web Service

// build.gradle.kts
plugins {
    id("java")
    id("org.springframework.boot") version "3.5.5"
    id("io.spring.dependency-management") version "1.1.7"
}

group = "com.waitrose"
version = "1.0.0"

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(21)
    }
}

repositories {
    mavenCentral()
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-web")
    implementation("org.springframework.boot:spring-boot-starter-actuator")

    testImplementation("org.springframework.boot:spring-boot-starter-test")
}

tasks.test {
    useJUnitPlatform()
}

tasks.bootJar {
    enabled = true
}

tasks.jar {
    enabled = false
}

Build and run:

./gradlew bootJar              # Create JAR: build/libs/app-1.0.0.jar
java -jar build/libs/app-1.0.0.jar  # Run JAR

For advanced examples including multi-module setups, layered JARs with Docker, build info injection, and testing configurations, see examples/advanced-examples.md.

Commands Reference

See references/commands-and-troubleshooting.md for complete command reference and troubleshooting guide.

About this skill

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