[[build-image]]
== Packaging OCI Images
The plugin can create an https://github.com/opencontainers/image-spec[OCI image] from executable jars using https://buildpacks.io[Cloud Native Buildpacks].
Images can be built using the `bootBuildImage` task.
The task is automatically created when the `java` plugin is applied and is an instance of {boot-build-image-javadoc}[`BootBuildImage`].



[[build-image-docker-daemon]]
=== 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 https://docs.docker.com/install/[Docker Engine] on all supported platforms without configuration.

Environment variables can be set to configure the `bootBuildImage` task to use the https://minikube.sigs.k8s.io/docs/tasks/docker_daemon/[Docker daemon provided by minikube].
The following table shows the environment variables and their values:

|===
| Environment variable | Description

| DOCKER_HOST 
| URL containing the host and port for the Docker daemon - e.g. `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)
|===

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



[[build-image-customization]]
=== Image Customizations
The plugin invokes a {buildpacks-reference}/concepts/components/builder/[builder] to orchestrate the generation of an image.
The builder includes multiple {buildpacks-reference}/concepts/components/buildpack[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:

|===
| Property | Command-line option | Description | Default value

| `builder`
| `--builder`
| Name of the Builder image to use.
| `gcr.io/paketo-buildpacks/builder:base-platform-api-0.3`

| `imageName`
| `--imageName`
| {spring-boot-api}/buildpack/platform/docker/type/ImageReference.html#of-java.lang.String-[Image name] for the generated image.
| `docker.io/library/${project.artifactId}:${project.version}`

| `environment`
|
| Environment variables that should be passed to the builder.
|

| `cleanCache`
|
| Whether to clean the cache before building.
| `false`

| `verboseLogging`
|
| Enables verbose logging of builder operations.
| `false`
|===



[[build-image-examples]]
=== Examples



[[build-image-example-custom-image-builder]]
==== Custom Image Builder
If you need to customize the builder used to create the image, configure the task as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-builder.gradle[tags=builder]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-builder.gradle.kts[tags=builder]
----

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



[[build-image-example-builder-configuration]]
==== Builder Configuration
If the builder exposes configuration options, those can be set using the `environment` property.

The following example assumes that the default builder defines a `BP_JAVA_VERSION` property (typically used to customize the JDK version the image should use):

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-env.gradle[tags=env]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-env.gradle.kts[tags=env]
----

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 default builder, this can be accomplished by setting the `HTTPS_PROXY` and/or `HTTP_PROXY` environment variables as show in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-env-proxy.gradle[tags=env]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-env-proxy.gradle.kts[tags=env]
----



[[build-image-example-custom-image-name]]
==== Custom Image Name
By default, the image name is inferred from the `artifactId` and the `version` of the project, something like `docker.io/library/${project.artifactId}:${project.version}`.
You can take control over the name by setting task properties, as shown in the following example:

[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
.Groovy
----
include::../gradle/packaging/boot-build-image-name.gradle[tags=image-name]
----

[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
.Kotlin
----
include::../gradle/packaging/boot-build-image-name.gradle.kts[tags=image-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.