NullPointer exception on mapModel

What version of the library are you using? -> 3.0.0 What kind of issue is this? -> Bug, Regression

When browsing v3/api-docs?group=api I get a Nullpointer Exception in SchemaMapper.java line 97. It seems like the mapFrom function returns null.

java.lang.NullPointerException: null
	at springfox.documentation.oas.mappers.SchemaMapper.model(SchemaMapper.java:97) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.SchemaMapper.mapModel(SchemaMapper.java:85) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapperImpl.fromRepresentation(ServiceModelToOpenApiMapperImpl.java:187) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapper.map(ServiceModelToOpenApiMapper.java:216) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapperImpl.mapOperation(ServiceModelToOpenApiMapperImpl.java:113) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapper.mapOperations(ServiceModelToOpenApiMapper.java:283) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapper.lambda$mapPaths$4(ServiceModelToOpenApiMapper.java:264) ~[springfox-oas-3.0.0.jar:3.0.0]
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) ~[?:?]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1655) ~[?:?]
	at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658) ~[?:?]
	at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:274) ~[?:?]
	at java.util.TreeMap$ValueSpliterator.forEachRemaining(TreeMap.java:2890) ~[?:?]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) ~[?:?]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) ~[?:?]
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) ~[?:?]
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) ~[?:?]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:?]
	at java.util.stream.ReferencePipeline.forEachOrdered(ReferencePipeline.java:502) ~[?:?]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapper.mapPaths(ServiceModelToOpenApiMapper.java:260) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.mappers.ServiceModelToOpenApiMapperImpl.mapDocumentation(ServiceModelToOpenApiMapperImpl.java:83) ~[springfox-oas-3.0.0.jar:3.0.0]
	at springfox.documentation.oas.web.OpenApiControllerWebMvc.getDocumentation(OpenApiControllerWebMvc.java:88) ~[springfox-oas-3.0.0.jar:3.0.0]

Variables at that time: source=ModelSpecification[scalar=null, compound=null, collection=null, map=null, reference=ReferenceModelSpecification{modelKey=ModelKey{qualifiedModelName=ModelName{namespace=‘’, name=‘null’}, viewDiscriminator=null, validationGroupDiscriminators=[], isResponse=true}}, facets=null, name=‘null’] facets=Optional.empty

The v2/api-docs?group=api endpoint is working and it worked before upgrading to version 3.0.0. Following operation/rest controller seems to trigger this (kotlin):

import io.swagger.annotations.Api
import io.swagger.annotations.ApiOperation
import io.swagger.annotations.ApiParam
import org.springframework.http.HttpStatus
import org.springframework.http.MediaType.APPLICATION_JSON_VALUE
import org.springframework.web.bind.annotation.RequestBody
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RequestMethod.POST
import org.springframework.web.bind.annotation.ResponseStatus
import org.springframework.web.bind.annotation.RestController

@RestController
@Api(tags = ["some tag"])
@Deprecated("no longer supported. ")
class RestController(private val service: SomeService) {
    @RequestMapping(path = [URL_CALL], method = [POST], consumes = [APPLICATION_JSON_VALUE])
    @ApiOperation(value = "Logs and stores a message")
    @ResponseStatus(value = HttpStatus.NO_CONTENT)
    fun call(
            @RequestBody
            @ApiParam(name = "call", value = "data to be stored")
            call: MutableMap<String, Any?>) {
        service.log(call)
    }

    companion object {
        const val URL_CALL = "api" + "/calls"
    }
}```

[kdebski85]

I confirm that returning ResponseEntity instead of void is a working workaround.

It is best to return ResponseEntity<Void>. You can return it with ResponseEntity.noContent().build().

I did some debugging and SchemaMapper fails when it tries to map response code 200. But there should not be that code at all. Void methods use result code 204 to indicate success.

[illidan80]

BTW, workaround is to return ResponseEntity<String> instead of void, like this:

@RestController
public class TestController {

    @ApiOperation("an endpoint")
    @PostMapping(value = "/endpoint/", consumes = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<String> endpoint () {
        // do stuff here
       return ResponseEntity.ok().build();
    }
}