1. Download the Java JAR (http://central.maven.org/maven2/org/openapitools/openapi-generator-cli/4.2.0/openapi-generator-cli-4.2.0.jar)

2. Rename the JAR as "openapi-generator-cli.jar"

3. Run the following command to generate a Java Vert.x Web server stub for the Petstore API (https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml):

Mac/Linux:

$ java -jar openapi-generator-cli.jar generate -g java-vertx-web -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o /var/tmp/java-vertx/

Windows:

$ java -jar openapi-generator-cli.jar generate -g java-vertx-web -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o C:\tmp\java-vertx

If you've any feedback or question, please let us know via https://github.com/OpenAPITools/openapi-generator/issues/new