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jlink.online is a HTTP microservice that builds optimized/minimized Java runtimes on the fly.

This project is currently experimental and subject to change at any time.

Introduction

This project is a wrapper for Java's jlink utility that makes it faster and easier to build custom Java runtimes for an application. Just send a HTTP request and jlink.online fetches the appropriate JDK (from AdoptOpenJDK), runs jlink to produce a custom runtime image containing your dependencies, then returns that compressed runtime in the response.

Using an optimized runtime is a good idea when deploying to a production environment or when bundling a platform-specific runtime to distribute with your application. For many applications, a jlink'd runtime will be significantly smaller in size.

Usage Examples

The following examples can be run interactively from the Swagger documentation.

Download a minimized Java 11 runtime for Linux x64 (containing java.base only)

https://jlink.online/runtime/x64/linux/11.0.8+10

Download a minimized Java 11 runtime for Linux x64 (containing java.desktop and jdk.zipfs)

https://jlink.online/runtime/x64/linux/11.0.8+10?modules=java.desktop,jdk.zipfs

Download a minimized runtime in a Dockerfile

# If you do 'FROM openjdk' then you'll get a full runtime
FROM alpine:latest

# Install dependencies
RUN apk add curl

# Install custom runtime
RUN curl -G 'https://jlink.online/runtime/x64/linux/11.0.8+10' \
    -d modules=java.base \
    | tar zxf -

# Install application
# ...

Upload your application's module-info.java (experimental)

Suppose your application has the following module definition:

module com.github.example {
    requires org.slf4j;
    ...
}

Then to build a custom runtime containing your dependencies, you can send a POST request containing your module-info.java:

curl --data-binary @com.github.example/src/main/java/module-info.java \
  'https://jlink.online/runtime/x64/linux/11.0.8+10?artifacts=org.slf4j:slf4j-api:2.0.0-alpha1' \
  --output app_runtime.tar.gz

The artifacts parameter is a comma-separated list of the Maven Central coordinates of your dependencies. This is required to know what versions to include in your runtime. In the future, we may be able to get this information from a build.gradle or pom.xml which would be much more convenient.

Unfortunately this can't work for dependencies that are automatic modules (because automatic modules don't specify their dependencies).

Credits

Thanks to the following projects:

  • gin - for handling HTTP requests
  • jlink - for minimizing runtime images
  • testify - for unit testing