cel-lab

Run using Docker

docker run --rm -p 8081:8081 michalklempa/cel-lab:latest

Browse to localhost:8081

Obtaining a .desc File for the UI

The UI evaluates CEL expressions against a message type loaded from a Protobuf descriptor set (FileDescriptorSet, conventionally a .desc file). Upload one in the UI, then pick the message type to evaluate against.

Generate the descriptor with protoc:

protoc --descriptor_set_out=out.desc --include_imports *.proto

• --descriptor_set_out is the output .desc path.
• --include_imports is required — it bundles every transitive import into a single self-contained file. Without it, CEL cannot resolve types referenced across .proto files and the upload will fail.

Any tool that emits a FileDescriptorSet works as well, for example Buf:

buf build -o out.desc

Project Structure

Source code for the UI part is located at:

src/main/java/com/michalklempa

The main entry point into the application is Application.java. This class contains the main() method that starts up the Spring Boot application.

In the src/main/java/com/michalklempa/base/ui is the MainLayout.java of the Application.

The only one screen of the application is actually a Playground to edit CEL expressions located in src/main/java/com/michalklempa/playground

Directory src/main/java/main/frontend can be ignored, it is generated during compilation.

Starting in Development Mode

To start the application in development mode:

mvn spring-boot:run

Building for Production

To build the application in production mode, run:

mvn package

To build a Docker image, run:

docker build -t my-application:latest .

Native Application Image (jpackage)

Bundles the app with a Java runtime into a self-contained launcher. Requires JDK 25 active; build on the OS/arch you target (no cross-compilation).

Linux — launcher at target/dist/cel-lab/bin/cel-lab:

mvn -Plinux-jpackage -DskipTests clean package

Windows — adds --win-console; launcher at target\dist\cel-lab\cel-lab.exe:

mvn -Pwindows-jpackage -DskipTests clean package