[Bug]: String and Boolean and Int properties are being turned into Objects in OpenAPI 3.1.0

[senahornby]

This is an issue specifically with OpenAPI Version 3.1.0. I am not having this issue with OpenAPI Version 3.0.X. My current workaround is to use OpenAPI 3.0.1.

I am using the Swagger Codegen Maven Plugin V3, version 3.0.71. I am using Java 21, Spring Boot 3.5.8. In my pom file I have the following configuration:

            <plugin>
                <groupId>io.swagger.codegen.v3</groupId>
                <artifactId>swagger-codegen-maven-plugin</artifactId>
                <version>3.0.71</version>
                <executions>
                    <execution>
                        <id>my-project</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.baseUri}/src/main/resources/myproject.json</inputSpec>
                            <language>java</language>
                            <library>resttemplate</library>
                            <generateApis>false</generateApis>
                            <modelPackage>com.my.project.model</modelPackage>
                            <generateApiTests>false</generateApiTests>
                            <generateApiDocumentation>false</generateApiDocumentation>
                            <generateModelTests>false</generateModelTests>
                            <generateModelDocumentation>false</generateModelDocumentation>
                            <generateSupportingFiles>false</generateSupportingFiles>
                            <configOptions>
                                <interfaceOnly>true</interfaceOnly>
                                <dateLibrary>legacy</dateLibrary>
                                <hideGenerationTimestamp>true</hideGenerationTimestamp>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

I am expecting the input JSON file to generate Java files that will match the json. However, upon running mvn clean generate-sources, I keep seeing the following warning: "[WARNING] String to be sanitized is null. Default to Object"

Here is an example of one of the objects in the JSON schema:

            "Doctor": {
                "type": "object",
                "properties": {
                    "code": {
                        "type": "string",
                        "format": "uuid"
                    },
                    "practiceName": {
                        "type": "string"
                    },
                    "address1": {
                        "type": "string"
                    },
                    "address2": {
                        "type": "string"
                    },
                    "address3": {
                        "type": "string"
                    },
                    "postalCode": {
                        "type": "string"
                    },
                    "townCity": {
                        "type": "string"
                    },
                    "regionCounty": {
                        "type": "string"
                    },
                    "country": {
                        "type": "string"
                    },
                    "email": {
                        "type": "string"
                    },
                    "phoneNumber": {
                        "type": "string"
                    },
                    "approved": {
                        "type": "boolean"
                    },
                    "externalId": {
                        "type": "integer",
                        "format": "int32"
                    },
                    "languageTag": {
                        "type": "string"
                    }
                }
            }

Okay, so you'd think that would product a Java object with properties matching the types described (strings, booleans). Instead, in the resulting Java object, every single property is just an Object.

public class Doctor {
  @JsonProperty("code")
  private Object code = null;

  @JsonProperty("practiceName")
  private Object practiceName = null;

  @JsonProperty("address1")
  private Object address1 = null;

  @JsonProperty("address2")
  private Object address2 = null;

  @JsonProperty("address3")
  private Object address3 = null;

  @JsonProperty("postalCode")
  private Object postalCode = null;

  @JsonProperty("townCity")
  private Object townCity = null;

  @JsonProperty("regionCounty")
  private Object regionCounty = null;

  @JsonProperty("country")
  private Object country = null;

  @JsonProperty("email")
  private Object email = null;

  @JsonProperty("phoneNumber")
  private Object phoneNumber = null;

  @JsonProperty("approved")
  private Object approved = null;

  @JsonProperty("externalId")
  private Object externalVetId = null;

  @JsonProperty("languageTag")
  private Object languageTag = null;

  public Doctor code(Object code) {
    this.code = code;
    return this;
  }

I want the properties (i.e. practiceName, country, etc.) to actually match what the schema has (i.e. both practiceName and country should be Strings).