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Guides

Spring Boot HTTP Server

This guide explains how to create and deploy a Spring Boot web server. To run this example, follow these steps:

1. Install the CLI. Use the unikraft CLI or the legacy kraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

   The unikraft CLI is the current standard, while kraft is the legacy version. Choose one of the CLIs below and only run the commands associated with it for the rest of this guide.

2. Clone the examples repository and cd into the examples/httpserver-java17-springboot3.5.x/ directory:

Code
git clone https://github.com/unikraft-cloud/examples
cd examples/httpserver-java17-springboot3.5.x/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

When done, invoke the following command to deploy this app on Unikraft Cloud:

The output shows the instance address and other details:

In this case, the instance name is httpserver-java17-springboot35x-qseeo and the address is https://long-dust-si7xsngk.fra.unikraft.app. They're different for each run.

Use curl to query the Spring Boot server's hello endpoint:

Code
curl https://long-dust-si7xsngk.fra.unikraft.app/hello

Code
Hello World!

When done, you can remove the instance:

Customize your app

To customize the app, update the files in the repository, listed below:

• DemoApplication.java: the server
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

Lines in the Kraftfile have the following roles:

• spec: v0.7: The current Kraftfile specification version is 0.7.

• runtime: base-compat:latest: The runtime kernel to use is the base compatibility kernel.

• rootfs: Build the app root filesystem. source: ./Dockerfile means the filesystem is built using the Dockerfile. format: erofs means the filesystem type is EROFS.

• cmd: ["/usr/lib/jvm/java-17-openjdk-amd64/bin/java", "-jar", "/usr/src/demo-0.0.1-SNAPSHOT.jar"]: Use as the starting command of the instance.

Lines in the Dockerfile have the following roles:

• FROM scratch: Build the filesystem from the scratch container image, to create a base image.

• COPY DemoApplication.java src/main/java/com/example/demo/: Copy the server implementation file in the Docker filesystem.

The following options are available for customizing the app:

• If you only update the implementation in the DemoApplication.java source file, you don't need to make any other changes.

• If you create any new source files, copy them into the app filesystem by using the COPY command in the Dockerfile.

• More extensive changes may require extending the Dockerfile (see Dockerfile syntax reference).

You can list information about the instance by running:

When done, you can remove the instance:

Learn more

Use the --help option for detailed information on using Unikraft Cloud:

Or visit the CLI Reference or the legacy CLI Reference.