Swagger oneOf type: Jackson trying to instantiate interface instead of implementation? - jackson

Question

I'm using the oneOf feature to define several possible schemas that can go into a request body property of my service. In the generated Java client code, the Java implementations of these schemas implement an interface, but when I send a request through, Jackson is trying to create an instance of the interface, instead of the concrete class.
Swagger-codegen version
<groupId>io.swagger.codegen.v3</groupId>
<artifactId>swagger-codegen-maven-plugin</artifactId>
<version>3.0.14</version>
Swagger declaration file content
schemas:
TestRequest:
description:
Test request
type:
object
required:
- criteria
properties:
criteria:
oneOf:
- $ref: '#/components/schemas/CriteriaA'
- $ref: '#/components/schemas/CriteriaB'
...
CriteriaA:
description: Criteria A
type: object
required:
- type
- query
properties:
type:
description: A description
type: string
enum:
- CriteriaA
query:
description: A query.
type: object
Steps to reproduce
The Java client code generated by swagger codegen looks like this:
Interface:
public interface OneOfTestRequestCriteria {}
Concrete class:
#Schema(description = "")
#javax.annotation.Generated(value = "io.swagger.codegen.v3.generators.java.JavaClientCodegen", date = "2020-01-28T13:06:29.942Z[Europe/London]")
public class CriteriaA implements OneOfTestRequestCriteria {
#JsonAdapter(TypeEnum.Adapter.class)
public enum TypeEnum {
CriteriaA("CriteriaA");
private String value;
TypeEnum(String value) {
this.value = value;
}
public String getValue() {
return value;
}
#Override
public String toString() {
return String.valueOf(value);
}
public static TypeEnum fromValue(String text) {
for (TypeEnum b : TypeEnum.values()) {
if (String.valueOf(b.value).equals(text)) {
return b;
}
}
return null;
}
public static class Adapter extends TypeAdapter<TypeEnum> {
#Override
public void write(final JsonWriter jsonWriter, final TypeEnum enumeration) throws IOException {
jsonWriter.value(enumeration.getValue());
}
#Override
public TypeEnum read(final JsonReader jsonReader) throws IOException {
String value = jsonReader.nextString();
return TypeEnum.fromValue(String.valueOf(value));
}
}
} #SerializedName("type")
private TypeEnum type = null;
#SerializedName("query")
private Object query = null;
public CriteriaA type(TypeEnum type) {
this.type = type;
return this;
}
#Schema(required = true, description = "")
public TypeEnum getType() {
return type;
}
public void setType(TypeEnum type) {
this.type = type;
}
public CriteriaA query(Object query) {
this.query = query;
return this;
}
#Schema(required = true, description = "")
public Object getQuery() {
return query;
}
public void setQuery(Object query) {
this.query = query;
}
#Override
public boolean equals(java.lang.Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
CriteriaA criteriaA = (CriteriaA ) o;
return Objects.equals(this.type, criteriaA.type) &&
Objects.equals(this.query, criteriaA.query);
}
#Override
public int hashCode() {
return Objects.hash(type, query);
}
#Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("class CriteriaA {\n");
sb.append(" type: ").append(toIndentedString(type)).append("\n");
sb.append(" query: ").append(toIndentedString(query)).append("\n");
sb.append("}");
return sb.toString();
}
private String toIndentedString(java.lang.Object o) {
if (o == null) {
return "null";
}
return o.toString().replace("\n", "\n ");
}
}
I'm trying to use this generated client code to send a request:
final TestRequest testRequest = new TestRequest();
final CriteriaA criteriaA = new CriteriaA ();
criteriaA .setType(CriteriaA .TypeEnum.CriteriaA);
criteriaA .setQuery("a query");
testRequest .setCriteria(criteriaA );
final ApiResponse<Void> apiResponse = testApi.createOrUpdateTestWithHttpInfo(testRequest);
Running the above client code results in this error when Jackson tries to deserialize it. It seems to be trying to construct an instance of the interface OneOfTestRequestCriteria, instead of the concrete implementation of the interface; CriteriaA:
[Request processing failed; nested exception is
org.springframework.http.converter.HttpMessageConversionException:
Type definition error: [simple type, class
com.acme.tag.models.OneOfTestRequestCriteria]; nested exception is
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot
construct instance of com.acme.tag.models.OneOfTestRequestCriteria (no
Creators, like default construct, exist): abstract types either need
to be mapped to concrete types, have custom deserializer, or contain
additional type information\n
If I annotate the generated interface:
public interface OneOfTestRequestCriteria {}
with the following:
#JsonTypeInfo(
use = JsonTypeInfo.Id.NAME,
include = JsonTypeInfo.As.PROPERTY,
property = "type")
#JsonSubTypes({
#Type(value = CriteriaA.class, name = "CriteriaA")
})
public interface OneOfTestRequestCriteria {
}
Then the request gets deserialized correctly into CriteriaA - am I missing something in my swagger.yaml that would result in this interface not getting annotated by the codegen tool?

Answer 1

<groupId>io.swagger.codegen.v3</groupId>
<artifactId>swagger-codegen-maven-plugin</artifactId>
<version>3.0.18</version>
See also: https://github.com/swagger-api/swagger-codegen-generators/pull/585