[BUG] Build failure with OpenJDK 16

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What’s the actual output vs expected output?
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Description

I would like to contribute to openapi-generator’s language support, but I’m not very familiar with Java, and the build is failing on my system.

❯ mvn clean install -e

[INFO] Running TestSuite
Configuring TestNG with: TestNG60Configurator
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
java.lang.instrument.IllegalClassFormatException: Error while instrumenting sun/util/resources/provider/NonBaseLocaleDataMetaInfo.
	at org.jacoco.agent.rt.internal_43f5073.CoverageTransformer.transform(CoverageTransformer.java:94)
...

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.1.0:jar (attach-javadocs) on project openapi-generator-core: MavenReportException: Error while generating Javadoc: Project contains Javadoc Warnings -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.1.0:jar (attach-javadocs) on project openapi-generator-core: MavenReportException: Error while generating Javadoc: Project contains Javadoc Warnings
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:215)

openapi-generator version

master (2e85ccdec8c3304e42c3434ef6da54a637a13e1a)

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

• clone https://github.com/OpenAPITools/openapi-generator.git
• mvn clean install -e

❯ java --version
openjdk 16.0.1 2021-04-20
OpenJDK Runtime Environment AdoptOpenJDK-16.0.1+9 (build 16.0.1+9)
OpenJDK 64-Bit Server VM AdoptOpenJDK-16.0.1+9 (build 16.0.1+9, mixed mode, sharing)

❯ mvn --version
Apache Maven 3.8.1 (05c21c65bdfed0f71a2f2ada8b84da59348c4c5d)
Maven home: /usr/local/Cellar/maven/3.8.1/libexec
Java version: 16.0.1, vendor: Homebrew, runtime: /usr/local/Cellar/openjdk/16.0.1/libexec/openjdk.jdk/Contents/Home
Default locale: en_CA, platform encoding: UTF-8
OS name: "mac os x", version: "11.4", arch: "x86_64", family: "mac"

Related issues/PRs

#9804 a different build error

Suggest a fix

[wing328]

Right, we’ve not yet tested this project with JDK 16. Please use ./run-in-docker.sh mvn package for the time being.

[Stokestack]

Same experience here. Skipping JavaDoc doesn’t solve it for me either. Java and Maven version info:

java version “1.8.0_341” Java™ SE Runtime Environment (build 1.8.0_341-b10) Java HotSpot™ 64-Bit Server VM (build 25.341-b10, mixed mode)

Apache Maven 3.8.6 (84538c9988a25aec085021c365c560670ad80f63) Maven home: /usr/local/Cellar/maven/3.8.6/libexec Java version: 18.0.2.1, vendor: Homebrew, runtime: /usr/local/Cellar/openjdk/18.0.2.1/libexec/openjdk.jdk/Contents/Home

The Docker option doesn’t work, because although I have Docker installed, the script mentioned above fails with:

docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

Aaaand this turns out to be a big PITA on Macs, which require a bunch of other stuff to run the Docker daemon, despite the fact that you can type “docker” at the command line and it spits out a bunch of info. Thus it would be really great to have the core problem fixed.