[JAVA] Maven codegen plugin fails under JDK17 in jknack handlebars library on reflection operation

Description

I'm building an application that needs to call rest services that are documented with an openapi.yaml file, and I need the API generated by Maven with the swagger-codegen-maven-plugin to be able to easily call and maintain the interface (which is still changing a little on the remote side).

Swagger-codegen version

3.0.29

Swagger declaration file content or url

<plugin>
        <groupId>io.swagger.codegen.v3</groupId>
        <artifactId>swagger-codegen-maven-plugin</artifactId>
        <version>3.0.29</version>
        <configuration>
          <inputSpec>${hif.deploy.url}/swagger-ui/openapi.v2.0.yaml</inputSpec>
          <configOptions>
            <sourceFolder>/</sourceFolder>
          </configOptions>
          <output>${project.build.directory}/generated-sources/rest-generated/</output>
          <language>java</language>
        </configuration>
        <executions>
          <execution>
            <id>generate-rest-v2-client</id>
            <phase>generate-sources</phase>
            <goals>
              <goal>generate</goal>
            </goals>
            <configuration>
              <language>java</language>
              <generateApiTests>false</generateApiTests>
              <generateModelTests>false</generateModelTests>
              <modelPackage>com.hansencx.hif.rest.v2.swagger.model</modelPackage>
              <apiPackage>com.hansencx.hif.rest.v2.swagger.api</apiPackage>
              <invokerPackage>com.hansencx.hif.rest.v2.swagger.invoker</invokerPackage>
              <inputSpec>${hif.deploy.url}/swagger-ui/openapi.v2.0.yaml</inputSpec>
            </configuration>
          </execution>
        </executions>
      </plugin>

Command line used for generation

open JDK 17
Maven 3.6.3
maven clean install

Steps to reproduce

1. select any valid openapi 3.0.1 yaml flie
2. create a new maven project with a compiler source and target value of 17 and the following dependencies needed for the generated code:

      <groupId>javax.annotation</groupId>
      <artifactId>javax.annotation-api</artifactId>
      <version>1.3.2</version>
    </dependency>
    <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.6.2</version>
      <type>jar</type>
    </dependency>
    <dependency>
      <groupId>io.swagger.core.v3</groupId>
      <artifactId>swagger-annotations</artifactId>
      <version>2.1.2</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.threeten/threetenbp -->
    <dependency>
      <groupId>org.threeten</groupId>
      <artifactId>threetenbp</artifactId>
      <version>1.5.1</version>
    </dependency>
    <dependency>
      <groupId>com.squareup.okhttp</groupId>
      <artifactId>okhttp</artifactId>
      <version>2.7.5</version>
    </dependency>
    <dependency>
      <groupId>com.squareup.okhttp</groupId>
      <artifactId>logging-interceptor</artifactId>
      <version>2.7.5</version>
    </dependency>
    <dependency>
      <groupId>io.gsonfire</groupId>
      <artifactId>gson-fire</artifactId>
      <version>1.8.3</version>
    </dependency>

3. Add the above plugin to the build system, and replace ${hif.deploy.url}/swagger-ui/openapi.v2.0.yaml with the URL of your selected
4. run maven clean install

Related issues/PRs

https://github.com/jknack/handlebars.java/pull/893

Suggest a fix/enhancement

Update handlebars-version in the parent pom.xml file from 4.1.2 to 4.3.0

Start with the handlebars-version entry in the parent pom.xml and review the related handlebars.java pull request. Run the Maven clean install reproduction on JDK 17; done means the swagger-codegen-maven-plugin completes generation without the reflection failure.