swagger-gradle-plugin - Support for ModelConverter

[peetzen]

I am experimenting with the new Swagger Gradle plugin and it works very well!
One important feature I am missing, is the possibility to add custom ModelConverter through the gradle resolve{} task configuration. There are configuration options for filterClass, readerClass and scannerClass but not for (multiple) ModelConverter classes.

Background:
I am using dropwizard with PropertyNamingStrategy.SNAKE_CASE for the ObjectMapper and want to generate a static openapi.yaml file through the gradle resolve{} task.

Code example:
Something that I am trying to achieve through the gradle task configuration could be similar to:

ModelConverters.getInstance().addConverter(new SnakeCaseConverter());

Custom Converter:

public class SnakeCaseConverter extends ModelResolver {

    public SnakeCaseConverter() {
        super(createMaper());
    }

    private static ObjectMapper createMaper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
        return mapper;
    }
}

[frantuma]

#2973 (available in 2.0.6-SNAPSHOT) introduces config properties objectMapperProcessorClass and modelConverterClasses, also available in maven and gradle plugins.

In your case objectMapperProcessorClass would match your needs: you would provide an implementation of io.swagger.v3.oas.integration.api.ObjectMapperProcessor interface, allowing to customize Jackson object mapper in use, and set objectMapperProcessorClass to the qualified class name of the processor implemenation class (see also https://github.com/swagger-api/swagger-core/wiki/Swagger-2.X---Integration-and-Configuration#configuration-properties)

something like:

public class SampleObjectMapperProcessor implements ObjectMapperProcessor {
    @Override
    public void processJsonObjectMapper(ObjectMapper mapper) {
        processYamlObjectMapper(mapper);
    }

    @Override
    public void processYamlObjectMapper(ObjectMapper mapper) {
        mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
    }
}

this will apply properties to objectMapper used by default by ModelResolver and other swagger components (e.g. the reader, etc). If you only want to process the mapper used by ModelResolver to resolve schemas, applying a converter like the one you shared, via the modelConverterClasses will do the trick.

closing ticket, please reopen if you're still experiencing issues

[peetzen]

@frantuma I gave it a try with the latest released version 2.0.6 and I run into a problem when running the resolve task.

I have implemented the ObjectMapperProcessor in default gradle buildSrc project.
In my main project I specify the ObjectMapper class as part of the resolve configuration:
objectMapperProcessorClass = 'de.peetzen.build.swagger.SnakeCaseObjectMapperProcessor'.

When I run the resolve task I get an ClassNotFoundException.

07:35:20.620 [Task worker for ':'] ERROR io.swagger.v3.oas.integration.GenericOpenApiContext - error initializing context: de.peetzen.build.swagger.SnakeCaseObjectMapperProcessor
java.lang.ClassNotFoundException: de.peetzen.build.swagger.SnakeCaseObjectMapperProcessor
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at io.swagger.v3.oas.integration.GenericOpenApiContext.buildObjectMapperProcessor(GenericOpenApiContext.java:267)
	at io.swagger.v3.oas.integration.GenericOpenApiContext.init(GenericOpenApiContext.java:361)
	at io.swagger.v3.oas.integration.GenericOpenApiContext.init(GenericOpenApiContext.java:28)
	at io.swagger.v3.jaxrs2.integration.JaxrsOpenApiContextBuilder.buildContext(JaxrsOpenApiContextBuilder.java:44)
	at io.swagger.v3.jaxrs2.integration.SwaggerLoader.resolve(SwaggerLoader.java:214)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at io.swagger.v3.plugins.gradle.tasks.ResolveTask.resolve(ResolveTask.java:388)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)

I would expect that the resolve task uses this special gradle buildSrc project by default to search for the class to load. How is this supposed to work? How do I have to define the dependency for the implementing class to be able to use it?

[frantuma]

Please add the buildSrc classpath to classpath parameter of resolveTask

[peetzen]

Thanks! I got a little bit further. Now I have the problem, that the change to the mapper actually affects the swagger internal json serialization schema as well and not just the payload data.

The swagger keyword additionalProperties (and any other swagger schema related parts) should not be handled with the same mapper instance, I guess. This is happening for me and causes an exception due to the affect on the keyword additional_properties. I use your suggested SampleObjectMapperProcessor code.

        at io.swagger.v3.plugins.gradle.tasks.ResolveTask.resolve(ResolveTask.java:388)
        ... 43 more
Caused by: java.lang.Exception: Error resolving API specification: additionalProperties must be either a Boolean or a Schema instance
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: io.swagger.v3.oas.models.media.ObjectSchema["additional_properties"])
        at io.swagger.v3.jaxrs2.integration.SwaggerLoader.resolve(SwaggerLoader.java:240)
        ... 44 more
Caused by: java.lang.IllegalArgumentException: additionalProperties must be either a Boolean or a Schema instance
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: io.swagger.v3.oas.models.media.ObjectSchema["additional_properties"])
        at com.fasterxml.jackson.databind.ObjectMapper._convert(ObjectMapper.java:3738)
        at com.fasterxml.jackson.databind.ObjectMapper.convertValue(ObjectMapper.java:3656)
        at io.swagger.v3.core.util.ModelDeserializer.deserializeObjectSchema(ModelDeserializer.java:106)
        at io.swagger.v3.core.util.ModelDeserializer.deserialize(ModelDeserializer.java:76)
        at io.swagger.v3.core.util.ModelDeserializer.deserialize(ModelDeserializer.java:28)
        at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001)
        at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2992)
        at io.swagger.v3.core.jackson.ModelResolver.resolve(ModelResolver.java:624)
        at io.swagger.v3.core.converter.ModelConverterContextImpl.resolve(ModelConverterContextImpl.java:90)
        at io.swagger.v3.core.jackson.ModelResolver.resolve(ModelResolver.java:617)
        at io.swagger.v3.core.converter.ModelConverterContextImpl.resolve(ModelConverterContextImpl.java:90)
        at io.swagger.v3.core.converter.ModelConverters.readAllAsResolvedSchema(ModelConverters.java:99)
        at io.swagger.v3.core.util.AnnotationsUtils.getSchema(AnnotationsUtils.java:1091)
        at io.swagger.v3.core.util.AnnotationsUtils.getSchema(AnnotationsUtils.java:1076)
        at io.swagger.v3.core.util.AnnotationsUtils.getContent(AnnotationsUtils.java:1032)
        at io.swagger.v3.jaxrs2.OperationParser.getApiResponses(OperationParser.java:91)
        at io.swagger.v3.jaxrs2.Reader.setOperationObjectFromApiOperationAnnotation(Reader.java:1125)
        at io.swagger.v3.jaxrs2.Reader.parseMethod(Reader.java:912)
        at io.swagger.v3.jaxrs2.Reader.parseMethod(Reader.java:772)
        at io.swagger.v3.jaxrs2.Reader.read(Reader.java:446)
        at io.swagger.v3.jaxrs2.Reader.read(Reader.java:169)
        at io.swagger.v3.jaxrs2.Reader.read(Reader.java:196)
        at io.swagger.v3.oas.integration.GenericOpenApiContext.read(GenericOpenApiContext.java:469)
        at io.swagger.v3.jaxrs2.integration.SwaggerLoader.resolve(SwaggerLoader.java:215)
        ... 44 more
Caused by: com.fasterxml.jackson.databind.JsonMappingException: additionalProperties must be either a Boolean or a Schema instance
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: io.swagger.v3.oas.models.media.ObjectSchema["additional_properties"])
        at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:277)
        at com.fasterxml.jackson.databind.deser.SettableBeanProperty._throwAsIOE(SettableBeanProperty.java:598)
        at com.fasterxml.jackson.databind.deser.SettableBeanProperty._throwAsIOE(SettableBeanProperty.java:586)
        at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:134)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:288)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
        at com.fasterxml.jackson.databind.ObjectMapper._convert(ObjectMapper.java:3733)
        ... 67 more
Caused by: java.lang.IllegalArgumentException: additionalProperties must be either a Boolean or a Schema instance
        at io.swagger.v3.oas.models.media.Schema.setAdditionalProperties(Schema.java:546)
        at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:132)
        ... 70 more

[frantuma]

Thanks for reporting, it is indeed a bug :( this should be fixed in #3038 (latest 2.0-7-SNAPSHOT) which limits the scope of custom ObjectMapper to default resolver; for 2.0.6, applying ModelConverter as in your example via modelConverters parameter should work:

modelConverterClasses = ["...SampleModelConverter"]

[peetzen]

Using the modelConverterClasses implementation worked as expected. Looking forward to 2.0.7!