@ParameterObject causes NPE when combined with spring-data-rest.

[broeser]

Describe the bug
I wanted to upgrade from Springdoc 1.3.9 on Spring Boot 2.3.1 to Springdoc 1.4.7 on Spring Boot 2.3.4

On opening the swagger-ui, I get the following exception:
java.lang.NullPointerException: null at org.springframework.core.annotation.AnnotationsScanner.getDeclaredAnnotations(AnnotationsScanner.java:459) at org.springframework.core.annotation.AnnotationsScanner.isKnownEmpty(AnnotationsScanner.java:492) at org.springframework.core.annotation.TypeMappedAnnotations.from(TypeMappedAnnotations.java:251) at org.springframework.core.annotation.MergedAnnotations.from(MergedAnnotations.java:351) at org.springframework.core.annotation.MergedAnnotations.from(MergedAnnotations.java:330) at org.springframework.core.annotation.AnnotatedElementUtils.findAnnotations(AnnotatedElementUtils.java:764) at org.springframework.core.annotation.AnnotatedElementUtils.findMergedAnnotation(AnnotatedElementUtils.java:632) at org.springdoc.core.AbstractRequestBuilder.build(AbstractRequestBuilder.java:243) at org.springdoc.api.AbstractOpenApiResource.calculatePath(AbstractOpenApiResource.java:372) at org.springdoc.api.AbstractOpenApiResource.calculatePath(AbstractOpenApiResource.java:505) at org.springdoc.webmvc.api.OpenApiResource.calculatePath(OpenApiResource.java:259) at org.springdoc.webmvc.api.OpenApiResource.getPaths(OpenApiResource.java:210) at org.springdoc.api.AbstractOpenApiResource.getOpenApi(AbstractOpenApiResource.java:268) at org.springdoc.webmvc.api.OpenApiResource.openapiJson(OpenApiResource.java:179) at org.springdoc.webmvc.api.MultipleOpenApiResource.openapiJson(MultipleOpenApiResource.java:200) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:878) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:792) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) …

I don't get an exception when I remove my @ParameterObject-annotations from my code.

To Reproduce
Steps to reproduce the behavior:

• What version of spring-boot you are using? 2.3.4

• What modules and versions of springdoc-openapi are you using?
  springdoc-openapi-ui 1.4.7
  springdoc-openapi-data-rest 1.4.7
  springdoc-openapi-security 1.4.7

• Provide with a sample code (HelloController) or Test that reproduces the problem
  The problem is easily reproducible with the following sample code:
  Controller:

@Validated
@RestController
@RequestMapping(value = {VERSION + "/helloWorld", "latest/helloWorld"}, produces = MediaType.APPLICATION_JSON_VALUE)
public class HelloController {

    @Operation(summary = "Example endpoint")
    @GetMapping("/helloWorld")
    public HelloWorldResponseModel helloWorld(@Valid @ParameterObject HelloWorldModel helloWorldModel, HttpServletRequest request) {
        return new HelloWorldResponseModel();
    }

}

The request parameter object "HelloWorldModel":

import io.swagger.v3.oas.annotations.Parameter;
import org.springframework.format.annotation.DateTimeFormat;

import javax.validation.constraints.NotBlank;
import javax.validation.constraints.NotNull;
import java.time.LocalDate;

public class HelloWorldModel {

    @Parameter(description = "Description for abc", example = "def")
    @NotBlank
    private String abc;

    @Parameter(description = "Description of this date", example = "2020-10-25")
    @NotNull
    @DateTimeFormat(iso = DateTimeFormat.ISO.DATE)
    private LocalDate thisDate;

    public String getAbc() {
        return abc;
    }

    public void setAbc(String abc) {
        this.abc = abc;
    }

    public LocalDate getThisDate() {
        return thisDate;
    }

    public void setThisDate(LocalDate thisDate) {
        this.thisDate = thisDate;
    }
}

The Application class:

// ...
    public static final String VERSION = "v1";

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public GroupedOpenApi v1() {
        return GroupedOpenApi.builder()
                             .group(VERSION)
                             .pathsToMatch("/" + VERSION + "/**")
                             .build();
    }

    @Bean
    public GroupedOpenApi latest() {
        return GroupedOpenApi.builder()
                             .group("latest")
                             .pathsToMatch("/latest/**")
                             .build();
    }

In case it matters, application.properties I used:

springdoc.swagger-ui.path=/doc
springdoc.paths-to-exclude=/
springdoc.api-docs.path=/api-docs

[bnasslahsen]

@broeser,

You sample code doesn't reference spring-data-rest. If you are not using spring-data-rest, then you can remove springdoc-openapi-data-rest and your issue will be fixed.

Otherwise, it's now fixed on master.