[BUG] Null pointer exception thrown when openapi doc has no components

[spacether]

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?
• [Optional] Sponsorship to speed up the bug fix or feature request

Description

Opening this issue per: #237 (comment)

Reported by @robin-nitrokey

Thanks! I tried to use 3.2.0 but it does not work for me:

• On the nethsm-sdk-py codebase, it does not generate path parameters.
• On the example from this issue, it causes a NullPointerException.
• On Example 1, it does not generate the path parameters either.
• On Example 2, I again get a NullPointerException.

Am I missing something?

Example 1

openapi: 3.0.0
info:
  title: NetHSM
  version: v1
servers:
  - url: https://{host}/api/{version}
    variables:
      host:
        default: localhost:8443
      version:
        default: v1
paths:
  /users/{UserID}:
    parameters:
      - name: UserID
        in: path
        required: true
        schema:
          type: string
    get:
      responses:
        "200":
          description: ""
          content:
            application/json:
              schema:
                type: string
      description: "Get user info: name and role."
components:
  securitySchemes:
    basic:
      description: |
        NetHSM supports Basic Authentication.
      type: http
      scheme: basic

Example 2

openapi: 3.0.0
info:
  title: NetHSM
  version: v1
servers:
  - url: https://{host}/api/{version}
    variables:
      host:
        default: localhost:8443
      version:
        default: v1
paths:
  /users/{UserID}:
    parameters:
      - name: UserID
        in: path
        required: true
        schema:
          type: string
    get:
      responses:
        "200":
          description: ""
          content:
            application/json:
              schema:
                type: string
      description: "Get user info: name and role."

NPE:

Exception in thread "main" java.lang.NullPointerException
        at org.openapijsonschematools.codegen.generatorrunner.DefaultGeneratorRunner.generateRequestBodies(DefaultGeneratorRunner.java:775)
        at org.openapijsonschematools.codegen.generatorrunner.DefaultGeneratorRunner.generate(DefaultGeneratorRunner.java:1456)
        at org.openapijsonschematools.codegen.clicommands.Generate.execute(Generate.java:441)
        at org.openapijsonschematools.codegen.clicommands.AbstractCommand.run(AbstractCommand.java:34)
        at org.openapijsonschematools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:76)

##### openapi-json-schema-generator version

3.2.0

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

[spacether]

This is caused by final Map<String, RequestBody> specRequestBodies = this.openAPI.getComponents().getRequestBodies(); throwing a npe because there are no components in your openapi document. I will post a PR to fix that issue.

[spacether]

The above PR ensures that components exist before accessing them