To download the Java Client v2 API jar, you can use the openapi-generator-cli package from the NPM Registry.

Here's a brief snippet to get you started:

npm install @openapitools/openapi-generator-cli

Then, run the following command to generate the Java client library:

openapi-generator-cli generate --input-spec https://example.com/openapi.json --generator-openapi-java --output-dir ./target/java-client

Replace https://example.com/openapi.json with the URL of your OpenAPI specification file.

This will generate a java-client.jar file in the ./target/java-client directory, which you can then use as a dependency in your Java project.