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

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).

Start with the Maven plugin configuration, the OpenAPI 3.1 input JSON, and the generated Doctor.java after running mvn clean generate-sources. Trace the warning "String to be sanitized is null. Default to Object" and compare the generated property types with the schema; done means string, boolean, and integer properties are generated with matching Java types instead of Object.