[BUG][JAVA] "jaxrs-spec" generator creates invalid nested enums with type number

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

If the OpenAPI definition contains a an enum of type number directly in the properties, an invalid Java enum is generated and the code does not compile. If the exact same enum is references however, the code is correct.

openapi-generator version

jaxrs-spec:7.5.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: test
  version: 0.0.1

paths:
  /test:
    get:
      responses:
        200:
          description: test
          content:
            application/json:
              schema:
                type: object
                properties:
                  inline:
                    type: number
                    enum: [ 0, 1, 2 ]
                  referenced:
                    $ref: '#/components/schemas/ReferencedEnum'

components:
  schemas:
    ReferencedEnum:
      type: number
      enum: [ 0, 1, 2 ]

Generation Details

I created a standard Maven project and ran it with mvn clean compile

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>Test</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <plugins>
      <plugin>
        <groupId>org.openapitools</groupId>
        <artifactId>openapi-generator-maven-plugin</artifactId>
        <version>7.5.0</version>
        <executions>
          <execution>
            <goals>
              <goal>generate</goal>
            </goals>
            <configuration>
              <inputSpec>${project.basedir}/src/main/resources/test.yaml</inputSpec>
              <generatorName>jaxrs-spec</generatorName>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Steps to reproduce

Running the above, ReferencedEnum is valid:

public enum ReferencedEnum {
  NUMBER_0(new BigDecimal("0")),
  NUMBER_1(new BigDecimal("1")),
  NUMBER_2(new BigDecimal("2"));
  private BigDecimal value;
// ...
}

However the nested InlineEnum is references a method that does not exist:

public enum InlineEnum {
    NUMBER_0(BigDecimal.valueOf(new BigDecimal("0"))),
    NUMBER_1(BigDecimal.valueOf(new BigDecimal("1"))),
    NUMBER_2(BigDecimal.valueOf(new BigDecimal("2")));
    private BigDecimal value;
// ...
}

The method BigDecimal.valurOf(BigDecimal) does not exist, which gives a compilation error.

Related issues/PRs

none

Suggest a fix

Generate the same enum code no matter whether it is a separate Schema or not.

Start with the jaxrs-spec generator and the provided OpenAPI declaration, then run the Maven reproduction using pom.xml and test.yaml. Compare the generated InlineEnum and ReferencedEnum; the work is done when both numeric enums use valid, equivalent Java code and mvn clean compile succeeds.