Using Java Native Image

Overview
Build using Cloud Native Buildpacks
- Example build Using Cloud Native Buildpacks
- Deploy using Cloud Native Buildpacks
Build using Native Build Tools
- Deploy with direct build
Spring Boot and Spring Native

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This topic tells you how to build Java apps with native image support and deploy those apps to Cloud Foundry.

Overview

A growing number of Java users are building Java apps using support for native images. For more information, see Native Image in the GraalVM documentation.

Java users deploying to Cloud Foundry can deploy apps compiled using native image support. However, the Cloud Foundry Java buildpack does not provide support to build, compile, and turn apps into a native image. You must perform those steps before deploying to Cloud Foundry.

To build your app that is suitable for running on Cloud Foundry, you can do one of the following:

Build Using Cloud Native Buildpacks
Build Using Native Build Tools

Build using Cloud Native Buildpacks

Cloud Native Buildpacks include support for building native image apps. You can pass in your source code or a compiled JAR and Cloud Native Buildpacks installs the required tools and builds a compatible image.

Example build Using Cloud Native Buildpacks

Clone the example repository from GitHub:

git clone https://github.com/paketo-buildpacks/samples
cd samples/java/native-image/java-native-image-sample

Build the example image:

./mvnw package
pack build apps/native-image -p target/demo-0.0.1-SNAPSHOT.jar -e BP_NATIVE_IMAGE=true -B paketobuildpacks/builder:tiny

For more information about building with Cloud Native Buildpacks, see Getting Started in the Spring Native documentation.

Deploy using Cloud Native Buildpacks

This section describes how to deploy a Java app with native image support using Cloud Native Buildpacks.

To deploy an app compiled using the steps from the previous section to Cloud Foundry, you can deploy the image directly using Cloud Foundry’s Docker support. If Docker support is deactivated, you can extract the native image binary from the container image and deploy the app using the binary buildpack.

Deploy from image

To deploy the app from an image:

Publish your image. You can do this in a number of ways. For example, you can use the --publish flag to pack build with docker tag and docker push, or through any other means of publishing a container image to a registry.

Validate that your foundation supports deploying Docker images by running the following command and confirming that diego_docker is set to enabled. If it is set to disabled, you cannot use this deployment option.

cf feature-flags

For example:

$ cf feature-flags Retrieving status of all flagged features as user@example.com...

features state user_org_creation disabled private_domain_creation enabled app_bits_upload enabled app_scaling enabled route_creation enabled service_instance_creation enabled diego_docker enabled set_roles_by_username enabled unset_roles_by_username enabled task_creation enabled env_var_visibility enabled space_scoped_private_broker_creation enabled space_developer_env_var_visibility enabled service_instance_sharing enabled hide_marketplace_from_unauthenticated_users disabled resource_matching enabled

Push your app by running:

cf push -o registry.example.com/apps/native-image native-image-app

Extract the image and deploy the Binary

To extract and deploy your app using the binary buildpack:

Create a script to extract the files:
```
#!/bin/bash

if [ -z "$1" ] || [ -z "$2" ]; then
    echo "USAGE: extract.sh image-name full-main-class"
    echo
    exit 1
fi

CONTAINER_ID=$(docker create "$1")
mkdir -p ./out
docker cp "$CONTAINER_ID:/workspace/$2" "./out/$2"
docker rm "$CONTAINER_ID" > /dev/null
```
This script is optional, but illustrates the process of extracting the binary file. It runs docker create and docker cp to extract the file from the image, followed by docker rm to remove the containerd. You can do this manually, or you can use any other tools for interacting with a container image.

Run the extract script:

$ ./extract.sh apps/native-image io.paketo.demo.Demoapp
$ file ./out/io.paketo.demo.Demoapp
io.paketo.demo.Demoapp: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=05cb81992f3859c9653a9ef6a691e798a9c48b9b, with debug_info, not stripped

The extract script places the binary in a directory called out under the current working directory. You can run file to examine it and confirm that it is a 64-bit Linux executable.

Push and run the compiled binary by running the following command. You can adjust other properties or use a manifest.yml file to deploy as well.
```
cf push -b binary_buildpack -m 256M -p ./out -c ./io.paketo.demo.Demoapp native-image
```

Build using Native Build Tools

This section describes how to deploy a Java app with native image support using Native Build Tools. If you do not want to build using Cloud Native Buildpacks, you can build and compile directly using the Native Build Tools.

To build a Java app using Native Build Tools:

Obtain an Ubuntu Bionic computer, VM, or container. Ubuntu Bionic is recommended for best compatibility with the Cloud Foundry cflinuxfs3 root filesystem. Ubuntu 22.04 LTS (Jammy Jellyfish) is recommended for use with cflinuxfs4.
Install GraalVM. See Get Started with GraalVM.
Install the Java Native Image tools. See Install Native Image.
To add the Native Build Tools to your Maven or Gradle project, follow the instructions in Add the native build tools plugin in the Spring documentation. This only needs to be done once.

Clone the example repository from GitHub:

git clone https://github.com/paketo-buildpacks/samples
cd samples/java/native-image/java-native-image-sample

Build the example image:
```
mvn -Pnative -DskipTests package
```

For more information about building with Native Build Tools, see Getting started with Native Build Tools in the Spring documentation.

Deploy with direct build

This section describes how to deploy a Java app with native image support using a direct build.

To deploy a Java app with native image support using the binary buildpack:

Zip the executable created by your build tool, either Maven or Gradle. For example, with Maven, zip demo.zip target/demo. Alternatively, you can copy the executable into a directory by itself. For example, with Maven, mkdir -p ./out && cp target/demo ./out/. This is the root for cf push.
Push the root ZIP file or directory you created in the previous step. If you use a directory instead of a ZIP archive, adjust the -p argument. This is important so that it only uploads the compiled binary, not your entire project. You can adjust other properties or use a manifest.yml file to deploy as well.
```
cf push -b binary_buildpack -p demo.zip -c ./target/demo native-image
```

Spring Boot and Spring Native

Regardless of how you build your app, with Spring Boot v2.5 and Spring Native v0.10.1, there is a bug that causes cf push to fail. The problem is caused by conditional behavior in Spring Boot Actuator when run on Cloud Foundry. It is fixed in Spring Native v0.10.2.

For more information, see the spring-projects-experimental repository on GitHub.

You can also work around this issue by adding the following hints above your @SpringBootapp annotation:

For example:

@NativeHint(trigger = ReactiveCloud FoundryActuatorAutoConfiguration.class, types = {
        @TypeHint(types = EndpointCloud FoundryExtension.class, access = AccessBits.ANNOTATION),
        @TypeHint(typeNames = "org.springframework.boot.actuate.autoconfigure.Cloud Foundry.Cloud FoundryEndpointFilter"),
        @TypeHint(typeNames = "org.springframework.boot.actuate.autoconfigure.Cloud Foundry.reactive.Cloud FoundryWebFluxEndpointHandlerMapping$Cloud FoundryLinksHandler", access = AccessBits.LOAD_AND_CONSTRUCT
                | AccessBits.DECLARED_METHODS) })
@NativeHint(trigger = Cloud FoundryActuatorAutoConfiguration.class, types = {
        @TypeHint(types = EndpointCloud FoundryExtension.class, access = AccessBits.ANNOTATION),
        @TypeHint(typeNames = "org.springframework.boot.actuate.autoconfigure.Cloud Foundry.Cloud FoundryEndpointFilter"),
        @TypeHint(typeNames = "org.springframework.boot.actuate.autoconfigure.Cloud Foundry.servlet.Cloud FoundryWebEndpointServletHandlerMapping$Cloud FoundryLinksHandler", access = AccessBits.LOAD_AND_CONSTRUCT
                | AccessBits.DECLARED_METHODS) })
@SpringBootapp
public class Demoapp {

    public static void main(String[] args) {
        Springapp.run(Demoapp.class, args);
    }

}

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