• 3.1. Managing Dependencies with the Dependency Management Plugin
  • 3.1.1. Customizing Managed Versions
  • 3.1.2. Using Spring Boot’s Dependency Management in Isolation
  • 3.1.3. Learning More
  • 3.2. Managing Dependencies with Gradle’s Bom Support
  • 3.2.1. Customizing Managed Versions
  • 4.3. Packaging Executable and Plain Archives
  • 4.4. Configuring Executable Archive Packaging
  • 4.4.1. Configuring the Main Class
  • 4.4.2. Including Development-only Dependencies
  • 4.4.3. Configuring Libraries that Require Unpacking
  • 4.4.4. Making an Archive Fully Executable
  • 4.4.5. Using the PropertiesLauncher
  • 4.4.6. Packaging Layered Jar or War
  • Custom Layers Configuration
  • 5.4.1. Custom Image Builder and Run Image
  • 5.4.2. Builder Configuration
  • 5.4.3. Runtime JVM Configuration
  • 5.4.4. Custom Image Name
  • 5.4.5. Buildpacks
  • 5.4.6. Image Publishing
  • 5.4.7. Builder Cache Configuration
  • 5.4.8. Docker Configuration
  • Docker Configuration for minikube
  • Docker Configuration for podman
  • Docker Configuration for Authentication
  • 6.1. Publishing with the Maven-publish Plugin
  • 6.2. Distributing with the Application Plugin
  • 7. Running your Application with Gradle
  • 7.1. Passing Arguments to your Application
  • 7.2. Passing System properties to your application
  • 7.3. Reloading Resources
  • 8. Ahead-of-Time Processing
  • 8.1. Processing Applications
  • 8.2. Processing Tests
  • 9. Integrating with Actuator
  • 9.1. Generating Build Information
  • 10. Reacting to Other Plugins
  • 10.1. Reacting to the Java Plugin
  • 10.2. Reacting to the Kotlin Plugin
  • 10.3. Reacting to the War Plugin
  • 10.4. Reacting to the Dependency Management Plugin
  • 10.5. Reacting to the Application Plugin
  • 10.6. Reacting to the GraalVM Native Image Plugin
  • The Spring Boot Gradle Plugin provides Spring Boot support in Gradle . It allows you to package executable jar or war archives, run Spring Boot applications, and use the dependency management provided by spring-boot-dependencies . Spring Boot’s Gradle plugin requires Gradle 7.x (7.5 or later) or 8.x and can be used with Gradle’s configuration cache .

    In addition to this user guide, API documentation is also available.

    The plugin is published to Gradle’s plugin portal and can be applied using the plugins block:

    Groovy
    plugins {
    	id 'org.springframework.boot' version '3.0.6'
    

    Applied in isolation the plugin makes few changes to a project. Instead, the plugin detects when certain other plugins are applied and reacts accordingly. For example, when the java plugin is applied a task for building an executable jar is automatically configured. A typical Spring Boot project will apply the groovy, java, or org.jetbrains.kotlin.jvm plugin as a minimum and also use the io.spring.dependency-management plugin or Gradle’s native bom support for dependency management. For example:

    Groovy
    plugins {
    	id 'java'
    	id 'org.springframework.boot' version '3.0.6'
    apply plugin: 'io.spring.dependency-management'
    

    To manage dependencies in your Spring Boot application, you can either apply the io.spring.dependency-management plugin or use Gradle’s native bom support. The primary benefit of the former is that it offers property-based customization of managed versions, while using the latter will likely result in faster builds.

    3.1. Managing Dependencies with the Dependency Management Plugin

    When you apply the io.spring.dependency-management plugin, Spring Boot’s plugin will automatically import the spring-boot-dependencies bom from the version of Spring Boot that you are using. This provides a similar dependency management experience to the one that’s enjoyed by Maven users. For example, it allows you to omit version numbers when declaring dependencies that are managed in the bom. To make use of this functionality, declare dependencies in the usual way but omit the version number:

    Groovy
    dependencies {
    	implementation('org.springframework.boot:spring-boot-starter-web')
    	implementation('org.springframework.boot:spring-boot-starter-data-jpa')
    
    dependencies {
    	implementation("org.springframework.boot:spring-boot-starter-web")
    	implementation("org.springframework.boot:spring-boot-starter-data-jpa")
    

    3.1.1. Customizing Managed Versions

    The spring-boot-dependencies bom that is automatically imported when the dependency management plugin is applied uses properties to control the versions of the dependencies that it manages. Browse the Dependency versions Appendix in the Spring Boot reference for a complete list of these properties.

    To customize a managed version you set its corresponding property. For example, to customize the version of SLF4J which is controlled by the slf4j.version property:

    Groovy
    ext['slf4j.version'] = '1.7.20'
    Each Spring Boot release is designed and tested against a specific set of third-party dependencies.
    Overriding versions may cause compatibility issues and should be done with care.
    

    3.1.2. Using Spring Boot’s Dependency Management in Isolation

    Spring Boot’s dependency management can be used in a project without applying Spring Boot’s plugin to that project. The SpringBootPlugin class provides a BOM_COORDINATES constant that can be used to import the bom without having to know its group ID, artifact ID, or version.

    First, configure the project to depend on the Spring Boot plugin but do not apply it:

    Groovy
    plugins {
    	id 'org.springframework.boot' version '3.0.6' apply false
    

    The Spring Boot plugin’s dependency on the dependency management plugin means that you can use the dependency management plugin without having to declare a dependency on it. This also means that you will automatically use the same version of the dependency management plugin as Spring Boot uses.

    Apply the dependency management plugin and then configure it to import Spring Boot’s bom:

    Groovy
    apply plugin: 'io.spring.dependency-management'
    dependencyManagement {
    	imports {
    		mavenBom org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES
    
    apply(plugin = "io.spring.dependency-management")
    the<DependencyManagementExtension>().apply {
    	imports {
    		mavenBom(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
    

    The Kotlin code above is a bit awkward. That’s because we’re using the imperative way of applying the dependency management plugin.

    We can make the code less awkward by applying the plugin from the root parent project, or by using the plugins block as we’re doing for the Spring Boot plugin. A downside of this method is that it forces us to specify the version of the dependency management plugin:

    plugins {
    	id("org.springframework.boot") version "3.0.6" apply false
    	id("io.spring.dependency-management") version "1.1.0"
    dependencyManagement {
    	imports {
    		mavenBom(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
    

    3.2. Managing Dependencies with Gradle’s Bom Support

    Gradle allows a bom to be used to manage a project’s versions by declaring it as a platform or enforcedPlatform dependency. A platform dependency treats the versions in the bom as recommendations and other versions and constraints in the dependency graph may cause a version of a dependency other than that declared in the bom to be used. An enforcedPlatform dependency treats the versions in the bom as requirements and they will override any other version found in the dependency graph.

    The SpringBootPlugin class provides a BOM_COORDINATES constant that can be used to declare a dependency upon Spring Boot’s bom without having to know its group ID, artifact ID, or version, as shown in the following example:

    Groovy
    dependencies {
    	implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
    
    dependencies {
    	implementation(platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES))
    

    A platform or enforced platform will only constrain the versions of the configuration in which it has been declared or that extend from the configuration in which it has been declared. As a result, in may be necessary to declare the same dependency in more than one configuration.

    3.2.1. Customizing Managed Versions

    When using Gradle’s bom support, you cannot use the properties from spring-boot-dependencies to control the versions of the dependencies that it manages. Instead, you must use one of the mechanisms that Gradle provides. One such mechanism is a resolution strategy. SLF4J’s modules are all in the org.slf4j group so their version can be controlled by configuring every dependency in that group to use a particular version, as shown in the following example:

    Groovy
    configurations.all {
    	resolutionStrategy.eachDependency { DependencyResolveDetails details ->
    		if (details.requested.group == 'org.slf4j') {
    			details.useVersion '1.7.20'
    
    configurations.all {
        resolutionStrategy.eachDependency {
            if (requested.group == "org.slf4j") {
                useVersion("1.7.20")
    Each Spring Boot release is designed and tested against a specific set of third-party dependencies.
    Overriding versions may cause compatibility issues and should be done with care.
    

    The plugin can create executable archives (jar files and war files) that contain all of an application’s dependencies and can then be run with java -jar.

    4.1. Packaging Executable Jars

    Executable jars can be built using the bootJar task. The task is automatically created when the java plugin is applied and is an instance of BootJar. The assemble task is automatically configured to depend upon the bootJar task so running assemble (or build) will also run the bootJar task.

    4.2. Packaging Executable Wars

    Executable wars can be built using the bootWar task. The task is automatically created when the war plugin is applied and is an instance of BootWar. The assemble task is automatically configured to depend upon the bootWar task so running assemble (or build) will also run the bootWar task.

    4.2.1. Packaging Executable and Deployable Wars

    A war file can be packaged such that it can be executed using java -jar and deployed to an external container. To do so, the embedded servlet container dependencies should be added to the providedRuntime configuration, for example:

    Groovy
    dependencies {
    	implementation('org.springframework.boot:spring-boot-starter-web')
    	providedRuntime('org.springframework.boot:spring-boot-starter-tomcat')
    
    dependencies {
    	implementation("org.springframework.boot:spring-boot-starter-web")
    	providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")
    

    4.3. Packaging Executable and Plain Archives

    By default, when the bootJar or bootWar tasks are configured, the jar or war tasks are configured to use plain as the convention for their archive classifier. This ensures that bootJar and jar or bootWar and war have different output locations, allowing both the executable archive and the plain archive to be built at the same time.

    If you prefer that the executable archive, rather than the plain archive, uses a classifier, configure the classifiers as shown in the following example for the jar and bootJar tasks:

    Groovy
    tasks.named("bootJar") {
    	archiveClassifier = 'boot'
    tasks.named("jar") {
    	archiveClassifier = ''
    

    Alternatively, if you prefer that the plain archive isn’t built at all, disable its task as shown in the following example for the jar task:

    Groovy
    tasks.named("jar") {
    	enabled = false
    

    4.4. Configuring Executable Archive Packaging

    The BootJar and BootWar tasks are subclasses of Gradle’s Jar and War tasks respectively. As a result, all of the standard configuration options that are available when packaging a jar or war are also available when packaging an executable jar or war. A number of configuration options that are specific to executable jars and wars are also provided.

    4.4.1. Configuring the Main Class

    By default, the executable archive’s main class will be configured automatically by looking for a class with a public static void main(String[]) method in the main source set’s output.

    The main class can also be configured explicitly using the task’s mainClass property:

    Groovy
    tasks.named("bootJar") {
    	mainClass = 'com.example.ExampleApplication'
    

    Alternatively, the main class name can be configured project-wide using the mainClass property of the Spring Boot DSL:

    Groovy
    springBoot {
    	mainClass = 'com.example.ExampleApplication'
    

    If the application plugin has been applied its mainClass property must be configured and can be used for the same purpose:

    Groovy
    application {
    	mainClass = 'com.example.ExampleApplication'
    
    tasks.named("bootJar") {
    	manifest {
    		attributes 'Start-Class': 'com.example.ExampleApplication'
    
    tasks.named<BootJar>("bootJar") {
    	manifest {
    		attributes("Start-Class" to "com.example.ExampleApplication")
    If the main class is written in Kotlin, the name of the generated Java class should be used.
    By default, this is the name of the Kotlin class with the Kt suffix added.
    For example, ExampleApplication becomes ExampleApplicationKt.
    If another name is defined using @JvmName then that name should be used.
    

    4.4.2. Including Development-only Dependencies

    By default all dependencies declared in the developmentOnly configuration will be excluded from an executable jar or war.

    If you want to include dependencies declared in the developmentOnly configuration in your archive, configure the classpath of its task to include the configuration, as shown in the following example for the bootWar task:

    Groovy
    tasks.named("bootWar") {
    	classpath configurations.developmentOnly
    

    4.4.3. Configuring Libraries that Require Unpacking

    Most libraries can be used directly when nested in an executable archive, however certain libraries can have problems. For example, JRuby includes its own nested jar support which assumes that jruby-complete.jar is always directly available on the file system.

    To deal with any problematic libraries, an executable archive can be configured to unpack specific nested jars to a temporary directory when the executable archive is run. Libraries can be identified as requiring unpacking using Ant-style patterns that match against the absolute path of the source jar file:

    Groovy
    tasks.named("bootJar") {
    	requiresUnpack '**/jruby-complete-*.jar'
    

    4.4.4. Making an Archive Fully Executable

    Spring Boot provides support for fully executable archives. An archive is made fully executable by prepending a shell script that knows how to launch the application. On Unix-like platforms, this launch script allows the archive to be run directly like any other executable or to be installed as a service.

    Currently, some tools do not accept this format so you may not always be able to use this technique. For example, jar -xf may silently fail to extract a jar or war that has been made fully-executable. It is recommended that you only enable this option if you intend to execute it directly, rather than running it with java -jar or deploying it to a servlet container.

    This will add Spring Boot’s default launch script to the archive. The default launch script includes several properties with sensible default values. The values can be customized using the properties property:

    Groovy
    tasks.named("bootJar") {
    	launchScript {
    		properties 'logFilename': 'example-app.log'
    
    tasks.named<BootJar>("bootJar") {
    	launchScript {
    		properties(mapOf("logFilename" to "example-app.log"))
    

    If the default launch script does not meet your needs, the script property can be used to provide a custom launch script:

    Groovy
    tasks.named("bootJar") {
    	launchScript {
    		script = file('src/custom.script')
    

    4.4.5. Using the PropertiesLauncher

    To use the PropertiesLauncher to launch an executable jar or war, configure the task’s manifest to set the Main-Class attribute:

    Groovy
    tasks.named("bootWar") {
    	manifest {
    		attributes 'Main-Class': 'org.springframework.boot.loader.PropertiesLauncher'
    
    tasks.named<BootWar>("bootWar") {
    	manifest {
    		attributes("Main-Class" to "org.springframework.boot.loader.PropertiesLauncher")
    

    4.4.6. Packaging Layered Jar or War

    By default, the bootJar task builds an archive that contains the application’s classes and dependencies in BOOT-INF/classes and BOOT-INF/lib respectively. Similarly, bootWar builds an archive that contains the application’s classes in WEB-INF/classes and dependencies in WEB-INF/lib and WEB-INF/lib-provided. For cases where a docker image needs to be built from the contents of the jar, it’s useful to be able to separate these directories further so that they can be written into distinct layers.

    Layered jars use the same layout as regular boot packaged jars, but include an additional meta-data file that describes each layer.

    By default, the following layers are defined:

    The layers order is important as it determines how likely previous layers can be cached when part of the application changes. The default order is dependencies, spring-boot-loader, snapshot-dependencies, application. Content that is least likely to change should be added first, followed by layers that are more likely to change.

    To disable this feature, you can do so in the following manner:

    Groovy
    tasks.named("bootJar") {
    	layered {
    		enabled = false
    

    When a layered jar or war is created, the spring-boot-jarmode-layertools jar will be added as a dependency to your archive. With this jar on the classpath, you can launch your application in a special mode which allows the bootstrap code to run something entirely different from your application, for example, something that extracts the layers. If you wish to exclude this dependency, you can do so in the following manner:

    Groovy
    tasks.named("bootJar") {
    	layered {
    		includeLayerTools = false
    
    Custom Layers Configuration

    Depending on your application, you may want to tune how layers are created and add new ones.

    This can be done using configuration that describes how the jar or war can be separated into layers, and the order of those layers. The following example shows how the default ordering described above can be defined explicitly:

    Groovy
    tasks.named("bootJar") {
    	layered {
    		application {
    			intoLayer("spring-boot-loader") {
    				include "org/springframework/boot/loader/**"
    			intoLayer("application")
    		dependencies {
    			intoLayer("application") {
    				includeProjectDependencies()
    			intoLayer("snapshot-dependencies") {
    				include "*:*:*SNAPSHOT"
    			intoLayer("dependencies")
    		layerOrder = ["dependencies", "spring-boot-loader", "snapshot-dependencies", "application"]
    		application {
    			intoLayer("spring-boot-loader") {
    				include("org/springframework/boot/loader/**")
    			intoLayer("application")
    		dependencies {
    			intoLayer("application") {
    				includeProjectDependencies()
    			intoLayer("snapshot-dependencies") {
    				include("*:*:*SNAPSHOT")
    			intoLayer("dependencies")
    		layerOrder.set(listOf("dependencies", "spring-boot-loader", "snapshot-dependencies", "application"))
    

    The application closure defines how the application classes and resources should be layered.

    The dependencies closure defines how dependencies should be layered.

    The layerOrder method defines the order that the layers should be written.

    Nested intoLayer closures are used within application and dependencies sections to claim content for a layer. These closures are evaluated in the order that they are defined, from top to bottom. Any content not claimed by an earlier intoLayer closure remains available for subsequent ones to consider.

    The intoLayer closure claims content using nested include and exclude calls. The application closure uses Ant-style path matching for include/exclude parameters. The dependencies section uses group:artifact[:version] patterns. It also provides includeProjectDependencies() and excludeProjectDependencies() methods that can be used to include or exclude project dependencies.

    If no include call is made, then all content (not claimed by an earlier closure) is considered.

    If no exclude call is made, then no exclusions are applied.

    Looking at the dependencies closure in the example above, we can see that the first intoLayer will claim all project dependencies for the application layer. The next intoLayer will claim all SNAPSHOT dependencies for the snapshot-dependencies layer. The third and final intoLayer will claim anything left (in this case, any dependency that is not a project dependency or a SNAPSHOT) for the dependencies layer.

    The application closure has similar rules. First claiming org/springframework/boot/loader/** content for the spring-boot-loader layer. Then claiming any remaining classes and resources for the application layer.

    The order that intoLayer closures are added is often different from the order that the layers are written. For this reason the layerOrder method must always be called and must cover all layers referenced by the intoLayer calls.

    The plugin can create an OCI image from a jar or war file using Cloud Native Buildpacks (CNB). Images can be built using the bootBuildImage task.

    The task is automatically created when the java or war plugin is applied and is an instance of BootBuildImage.

    5.1. Docker Daemon

    The bootBuildImage task requires access to a Docker daemon. By default, it will communicate with a Docker daemon over a local connection. This works with Docker Engine on all supported platforms without configuration.

    Environment variables can be set to configure the bootBuildImage task to use an alternative local or remote connection. The following table shows the environment variables and their values:

    DOCKER_HOST

    URL containing the host and port for the Docker daemon - for example tcp://192.168.99.100:2376

    DOCKER_TLS_VERIFY

    Enable secure HTTPS protocol when set to 1 (optional)

    DOCKER_CERT_PATH

    Path to certificate and key files for HTTPS (required if DOCKER_TLS_VERIFY=1, ignored otherwise)

    Docker daemon connection information can also be provided using docker properties in the plugin configuration. The following table summarizes the available properties:

    URL containing the host and port for the Docker daemon - for example tcp://192.168.99.100:2376

    tlsVerify

    Enable secure HTTPS protocol when set to true (optional)

    certPath

    Path to certificate and key files for HTTPS (required if tlsVerify is true, ignored otherwise)

    bindHostToBuilder

    When true, the value of the host property will be provided to the container that is created for the CNB builder (optional)

    5.2. Docker Registry

    If the Docker images specified by the builder or runImage properties are stored in a private Docker image registry that requires authentication, the authentication credentials can be provided using docker.builderRegistry properties.

    If the generated Docker image is to be published to a Docker image registry, the authentication credentials can be provided using docker.publishRegistry properties.

    Properties are provided for user authentication or identity token authentication. Consult the documentation for the Docker registry being used to store images for further information on supported authentication methods.

    The following table summarizes the available properties for docker.builderRegistry and docker.publishRegistry:

    email

    E-mail address for the Docker image registry user. Optional for user authentication.

    token

    Identity token for the Docker image registry user. Required for token authentication.

    5.3. Image Customizations

    The plugin invokes a builder to orchestrate the generation of an image. The builder includes multiple buildpacks that can inspect the application to influence the generated image. By default, the plugin chooses a builder image. The name of the generated image is deduced from project properties.

    Task properties can be used to configure how the builder should operate on the project. The following table summarizes the available properties and their default values:

    --builder

    Name of the Builder image to use.

    paketobuildpacks/builder:base or paketobuildpacks/builder:tiny when GraalVM Native Image plugin is applied.

    runImage

    --runImage

    Name of the run image to use.

    No default value, indicating the run image specified in Builder metadata should be used.

    imageName

    --imageName

    Image name for the generated image.

    docker.io/library/${project.name}:${project.version}

    pullPolicy

    --pullPolicy

    Policy used to determine when to pull the builder and run images from the registry. Acceptable values are ALWAYS, NEVER, and IF_NOT_PRESENT.

    ALWAYS

    environment

    Environment variables that should be passed to the builder.

    Empty or ['BP_NATIVE_IMAGE': 'true'] when GraalVM Native Image plugin is applied.

    buildpacks

    Buildpacks that the builder should use when building the image. Only the specified buildpacks will be used, overriding the default buildpacks included in the builder. Buildpack references must be in one of the following forms:

    Volume bind mounts that should be mounted to the builder container when building the image. The bindings will be passed unparsed and unvalidated to Docker when creating the builder container. Bindings must be in one of the following forms:

    buildCache

    A cache containing layers created by buildpacks and used by the image building process.

    A named volume in the Docker daemon, with a name derived from the image name.

    launchCache

    A cache containing layers created by buildpacks and used by the image launching process.

    A named volume in the Docker daemon, with a name derived from the image name.

    The plugin detects the target Java compatibility of the project using the JavaPlugin’s targetCompatibility property. When using the default Paketo builder and buildpacks, the plugin instructs the buildpacks to install the same Java version. You can override this behaviour as shown in the builder configuration examples.

    5.4.1. Custom Image Builder and Run Image

    If you need to customize the builder used to create the image or the run image used to launch the built image, configure the task as shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	builder = "mine/java-cnb-builder"
    	runImage = "mine/java-cnb-run"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	builder.set("mine/java-cnb-builder")
    	runImage.set("mine/java-cnb-run")
    

    This configuration will use a builder image with the name mine/java-cnb-builder and the tag latest, and the run image named mine/java-cnb-run and the tag latest.

    The builder and run image can be specified on the command line as well, as shown in this example:

    $ gradle bootBuildImage --builder=mine/java-cnb-builder --runImage=mine/java-cnb-run

    5.4.2. Builder Configuration

    If the builder exposes configuration options, those can be set using the environment property.

    The following is an example of configuring the JVM version used by the Paketo Java buildpacks at build time:

    Groovy
    tasks.named("bootBuildImage") {
    	environment["BP_JVM_VERSION"] = "17"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	environment.set(environment.get() + mapOf("BP_JVM_VERSION" to "17"))
    

    If there is a network proxy between the Docker daemon the builder runs in and network locations that buildpacks download artifacts from, you will need to configure the builder to use the proxy. When using the Paketo builder, this can be accomplished by setting the HTTPS_PROXY and/or HTTP_PROXY environment variables as show in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	environment["HTTP_PROXY"] = "http://proxy.example.com"
    	environment["HTTPS_PROXY"] = "https://proxy.example.com"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	environment.set(mapOf("HTTP_PROXY" to "http://proxy.example.com",
    						"HTTPS_PROXY" to "https://proxy.example.com"))
    

    5.4.3. Runtime JVM Configuration

    Paketo Java buildpacks configure the JVM runtime environment by setting the JAVA_TOOL_OPTIONS environment variable. The buildpack-provided JAVA_TOOL_OPTIONS value can be modified to customize JVM runtime behavior when the application image is launched in a container.

    Environment variable modifications that should be stored in the image and applied to every deployment can be set as described in the Paketo documentation and shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	environment["BPE_DELIM_JAVA_TOOL_OPTIONS"] = " "
    	environment["BPE_APPEND_JAVA_TOOL_OPTIONS"] = "-XX:+HeapDumpOnOutOfMemoryError"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	environment.set(mapOf(
    		"BPE_DELIM_JAVA_TOOL_OPTIONS" to " ",
    		"BPE_APPEND_JAVA_TOOL_OPTIONS" to "-XX:+HeapDumpOnOutOfMemoryError"
    

    5.4.4. Custom Image Name

    By default, the image name is inferred from the name and the version of the project, something like docker.io/library/${project.name}:${project.version}. You can take control over the name by setting task properties, as shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	imageName = "example.com/library/${project.name}"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	imageName.set("example.com/library/${project.name}")
    

    Note that this configuration does not provide an explicit tag so latest is used. It is possible to specify a tag as well, either using ${project.version}, any property available in the build or a hardcoded version.

    The image name can be specified on the command line as well, as shown in this example:

    $ gradle bootBuildImage --imageName=example.com/library/my-app:v1

    5.4.5. Buildpacks

    By default, the builder will use buildpacks included in the builder image and apply them in a pre-defined order. An alternative set of buildpacks can be provided to apply buildpacks that are not included in the builder, or to change the order of included buildpacks. When one or more buildpacks are provided, only the specified buildpacks will be applied.

    The following example instructs the builder to use a custom buildpack packaged in a .tgz file, followed by a buildpack included in the builder.

    Groovy
    tasks.named("bootBuildImage") {
    	buildpacks = ["file:///path/to/example-buildpack.tgz", "urn:cnb:builder:paketo-buildpacks/java"]
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	buildpacks.set(listOf("file:///path/to/example-buildpack.tgz", "urn:cnb:builder:paketo-buildpacks/java"))
    

    5.4.6. Image Publishing

    The generated image can be published to a Docker registry by enabling a publish option.

    If the Docker registry requires authentication, the credentials can be configured using docker.publishRegistry properties. If the Docker registry does not require authentication, the docker.publishRegistry configuration can be omitted.

    The registry that the image will be published to is determined by the registry part of the image name (docker.example.com in these examples). If docker.publishRegistry credentials are configured and include a url property, this value is passed to the registry but is not used to determine the publishing registry location.
    tasks.named("bootBuildImage") {
    	imageName.set("docker.example.com/library/${project.name}")
    	publish = true
    	docker {
    		publishRegistry {
    			username = "user"
    			password = "secret"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	imageName.set("docker.example.com/library/${project.name}")
    	publish.set(true)
    	docker {
    		publishRegistry {
    			username.set("user")
    			password.set("secret")
    

    5.4.7. Builder Cache Configuration

    The CNB builder caches layers that are used when building and launching an image. By default, these caches are stored as named volumes in the Docker daemon with names that are derived from the full name of the target image. If the image name changes frequently, for example when the project version is used as a tag in the image name, then the caches can be invalidated frequently.

    The cache volumes can be configured to use alternative names to give more control over cache lifecycle as shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	buildCache {
    		volume {
    			name = "cache-${rootProject.name}.build"
    	launchCache {
    		volume {
    			name = "cache-${rootProject.name}.launch"
    
    Docker Configuration for minikube

    The plugin can communicate with the Docker daemon provided by minikube instead of the default local connection.

    On Linux and macOS, environment variables can be set using the command eval $(minikube docker-env) after minikube has been started.

    The plugin can also be configured to use the minikube daemon by providing connection details similar to those shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	docker {
    		host = "tcp://192.168.99.100:2376"
    		tlsVerify = true
    		certPath = "/home/user/.minikube/certs"
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	docker {
    		host.set("tcp://192.168.99.100:2376")
    		tlsVerify.set(true)
    		certPath.set("/home/user/.minikube/certs")
    
    Docker Configuration for podman

    The plugin can communicate with a podman container engine.

    The plugin can be configured to use podman local connection by providing connection details similar to those shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	docker {
    		host = "unix:///run/user/1000/podman/podman.sock"
    		bindHostToBuilder = true
    
    tasks.named<BootBuildImage>("bootBuildImage") {
    	docker {
    		host.set("unix:///run/user/1000/podman/podman.sock")
    		bindHostToBuilder.set(true)
    
    Docker Configuration for Authentication

    If the builder or run image are stored in a private Docker registry that supports user authentication, authentication details can be provided using docker.builderRegistry properties as shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	docker {
    		builderRegistry {
    			username = "user"
    			password = "secret"
    			url = "https://docker.example.com/v1/"
    			email = "[email protected]"
    			password.set("secret")
    			url.set("https://docker.example.com/v1/")
    			email.set("[email protected]")
    

    If the builder or run image is stored in a private Docker registry that supports token authentication, the token value can be provided using docker.builderRegistry as shown in the following example:

    Groovy
    tasks.named("bootBuildImage") {
    	docker {
    		builderRegistry {
    			token = "9cbaf023786cd7..."
    

    6.1. Publishing with the Maven-publish Plugin

    To publish your Spring Boot jar or war, add it to the publication using the artifact method on MavenPublication. Pass the task that produces that artifact that you wish to publish to the artifact method. For example, to publish the artifact produced by the default bootJar task:

    Groovy
    publishing {
    	publications {
    		bootJava(MavenPublication) {
    			artifact tasks.named("bootJar")
    	repositories {
    		maven {
    			url 'https://repo.example.com'
    

    6.2. Distributing with the Application Plugin

    When the application plugin is applied a distribution named boot is created. This distribution contains the archive produced by the bootJar or bootWar task and scripts to launch it on Unix-like platforms and Windows. Zip and tar distributions can be built by the bootDistZip and bootDistTar tasks respectively. To use the application plugin, its mainClassName property must be configured with the name of your application’s main class.

    The bootRun task is an instance of BootRun which is a JavaExec subclass. As such, all of the usual configuration options for executing a Java process in Gradle are available to you. The task is automatically configured to use the runtime classpath of the main source set.

    By default, the main class will be configured automatically by looking for a class with a public static void main(String[]) method in the main source set’s output.

    The main class can also be configured explicitly using the task’s main property:

    Groovy
    tasks.named("bootRun") {
    	mainClass = 'com.example.ExampleApplication'
    

    Alternatively, the main class name can be configured project-wide using the mainClass property of the Spring Boot DSL:

    Groovy
    springBoot {
    	mainClass = 'com.example.ExampleApplication'
    

    By default, bootRun will configure the JVM to optimize its launch for faster startup during development. This behavior can be disabled by using the optimizedLaunch property, as shown in the following example:

    Groovy
    tasks.named("bootRun") {
    	optimizedLaunch = false
    

    If the application plugin has been applied, its mainClass property must be configured and can be used for the same purpose:

    Groovy
    application {
    	mainClass = 'com.example.ExampleApplication'
    

    7.1. Passing Arguments to your Application

    Like all JavaExec tasks, arguments can be passed into bootRun from the command line using --args='<arguments>' when using Gradle 4.9 or later. For example, to run your application with a profile named dev active the following command can be used:

    $ ./gradlew bootRun --args='--spring.profiles.active=dev'

    See the javadoc for JavaExec.setArgsString for further details.

    7.2. Passing System properties to your application

    Since bootRun is a standard JavaExec task, system properties can be passed to the application’s JVM by specifying them in the build script. To make that value of a system property to be configurable set its value using a project property. To allow a project property to be optional, reference it using findProperty. Doing so also allows a default value to be provided using the ?: Elvis operator, as shown in the following example:

    Groovy
    tasks.named("bootRun") {
    	systemProperty 'com.example.property', findProperty('example') ?: 'default'
    
    tasks.named<BootRun>("bootRun") {
    	systemProperty("com.example.property", findProperty("example") ?: "default")
    

    The preceding example sets that com.example.property system property to the value of the example project property. If the example project property has not been set, the value of the system property will be default.

    Gradle allows project properties to be set in a variety of ways, including on the command line using the -P flag, as shown in the following example:

    $ ./gradlew bootRun -Pexample=custom

    The preceding example sets the value of the example project property to custom. bootRun will then use this as the value of the com.example.property system property.

    7.3. Reloading Resources

    If devtools has been added to your project it will automatically monitor your application’s classpath for changes. Note that modified files need to be recompiled for the classpath to update in order to trigger reloading with devtools. For more details on using devtools, refer to this section of the reference documentation.

    Alternatively, you can configure bootRun such that your application’s static resources are loaded from their source location:

    Groovy
    tasks.named("bootRun") {
    	sourceResources sourceSets.main
    

    Spring AOT is a process that analyzes your code at build-time in order to generate an optimized version of it. It is most often used to help generate GraalVM native images.

    The Spring Boot Gradle plugin provides tasks that can be used to perform AOT processing on both application and test code. The tasks are configured automatically when the GraalVM Native Image plugin is applied:

    Groovy
    plugins {
    	id 'org.springframework.boot' version '3.0.6'
    	id 'org.graalvm.buildtools.native' version '0.9.21'
    	id 'java'
    
    plugins {
    	id("org.springframework.boot") version "3.0.6"
    	id("org.graalvm.buildtools.native") version "0.9.21"
    

    8.1. Processing Applications

    Based on your @SpringBootApplication-annotated main class, the processAot task generates a persistent view of the beans that are going to be contributed at runtime in a way that bean instantiation is as straightforward as possible. Additional post-processing of the factory is possible using callbacks. For instance, these are used to generate the necessary reflection configuration that GraalVM needs to initialize the context in a native image.

    As the BeanFactory is fully prepared at build-time, conditions are also evaluated. This has an important difference compared to what a regular Spring Boot application does at runtime. For instance, if you want to opt-in or opt-out for certain features, you need to configure the environment used at build time to do so. To this end, the processAot task is a JavaExec task and can be configured with environment variables, system properties, and arguments as needed.

    The nativeCompile task of the GraalVM Native Image plugin is automatically configured to use the output of the processAot task.

    8.2. Processing Tests

    The AOT engine can be applied to JUnit 5 tests that use Spring’s Test Context Framework. Suitable tests are processed by the processTestAot task to generate ApplicationContextInitialzer code. As with application AOT processing, the BeanFactory is fully prepared at build-time. As with processAot, the processTestAot task is JavaExec subclass and can be configured as needed to influence this processing.

    The nativeTest task of the GraalVM Native Image plugin is automatically configured to use the output of the processAot and processTestAot tasks.

    9.1. Generating Build Information

    Spring Boot Actuator’s info endpoint automatically publishes information about your build in the presence of a META-INF/build-info.properties file. A BuildInfo task is provided to generate this file. The easiest way to use the task is through the plugin’s DSL:

    Groovy
    springBoot {
    	buildInfo()
    

    This will configure a BuildInfo task named bootBuildInfo and, if it exists, make the Java plugin’s classes task depend upon it. The task’s destination directory will be META-INF in the output directory of the main source set’s resources (typically build/resources/main).

    By default, the generated build information is derived from the project:

    To exclude any of the default properties from the generated build information, add its name to the excludes. For example, the time property can be excluded as follows:

    Groovy
    springBoot {
    	buildInfo {
    		excludes = ['time']
    

    The default value for build.time is the instant at which the project is being built. A side-effect of this is that the task will never be up-to-date. As a result, builds will take longer as more tasks, including the project’s tests, will have to be executed. Another side-effect is that the task’s output will always change and, therefore, the build will not be truly repeatable. If you value build performance or repeatability more highly than the accuracy of the build.time property, exclude the time property as shown in the preceding example.

    Additional properties can also be added to the build information:

    Groovy
    springBoot {
    	buildInfo {
    		properties {
    			additional = [
    				'a': 'alpha',
    				'b': 'bravo'
    

    When another plugin is applied the Spring Boot plugin reacts by making various changes to the project’s configuration. This section describes those changes.

    10.1. Reacting to the Java Plugin

    When Gradle’s java plugin is applied to a project, the Spring Boot plugin:

    Creates a BootJar task named bootJar that will create an executable, fat jar for the project. The jar will contain everything on the runtime classpath of the main source set; classes are packaged in BOOT-INF/classes and jars are packaged in BOOT-INF/lib

    Configures the assemble task to depend on the bootJar task.

    Configures the jar task to use plain as the convention for its archive classifier.

    Creates a BootBuildImage task named bootBuildImage that will create a OCI image using a buildpack.

    Creates a BootRun task named bootRun that can be used to run your application.

    Creates a configuration named bootArchives that contains the artifact produced by the bootJar task.

    Creates a configuration named developmentOnly for dependencies that are only required at development time, such as Spring Boot’s Devtools, and should not be packaged in executable jars and wars.

    Creates a configuration named productionRuntimeClasspath. It is equivalent to runtimeClasspath minus any dependencies that only appear in the developmentOnly configuration.

    Configures any JavaCompile tasks with no configured encoding to use UTF-8.

    Configures any JavaCompile tasks to use the -parameters compiler argument.

    Aligns the Kotlin version used in Spring Boot’s dependency management with the version of the plugin. This is achieved by setting the kotlin.version property with a value that matches the version of the Kotlin plugin.

    Configures any KotlinCompile tasks to use the -java-parameters compiler argument.

    Creates a BootWar task named bootWar that will create an executable, fat war for the project. In addition to the standard packaging, everything in the providedRuntime configuration will be packaged in WEB-INF/lib-provided.

    Configures the assemble task to depend on the bootWar task.

    Configures the war task to use plain as the convention for its archive classifier.

    Configures the bootArchives configuration to contain the artifact produced by the bootWar task.

    Creates a CreateStartScripts task named bootStartScripts that will create scripts that launch the artifact in the bootArchives configuration using java -jar. The task is configured to use the applicationDefaultJvmArgs property as a convention for its defaultJvmOpts property.

    Creates a new distribution named boot and configures it to contain the artifact in the bootArchives configuration in its lib directory and the start scripts in its bin directory.

    Configures the bootRun task to use the mainClassName property as a convention for its main property.

    Configures the bootRun task to use the applicationDefaultJvmArgs property as a convention for its jvmArgs property.

    Configures the bootJar task to use the mainClassName property as a convention for the Start-Class entry in its manifest.

    Configures the bootWar task to use the mainClassName property as a convention for the Start-Class entry in its manifest.

    Registers a ProcessAot task named processAot that will generate AOT-optimized source for the application in the aot source set.

    Configures the Java compilation and process resources tasks for the aot source set to depend upon processAot.

    Registers a ProcessTestAot task named processTestAot that will generated AOT-optimized source for the application’s tests in the aotTest source set.

    Configures the Java compilation and process resources tasks for the aotTest source set to depend upon processTestAot.

    Adds the output of the aot source set to the classpath of the main GraalVM native binary.

    Adds the output of the aotTest source set to the classpath of the test GraalVM native binary.

    Configures the GraalVM extension to disable Toolchain detection.

    Configures each GraalVM native binary to require GraalVM 22.3 or later.

    Configures the bootJar task to include the reachability metadata produced by the collectReachabilityMetadata task in its jar.

    Configures the bootBuildImage task to use paketobuildpacks/builder:tiny as its builder and to set BP_NATIVE_IMAGE to true in its environment.