openapi-generator: [BUG][spring] Enum query parameter parsing fails due to enum constants being generated in uppercase

Ran into this issue today. What worked for is creating a custom Converter in Spring boot to convert the Enum to String

@Component
public class MyCustomEnumConverter implements Converter<String, SortEnum> {
    @Override
    public SortEnum convert(String source) {
       try {
          return SortEnum.valueOf(source);
       } catch(Exception e) {
          return null; // or SortEnum.asc
       }
    }
}

same situation

schema

    imgFormat:
      type: string
      enum:
        - "lol"
        - "image/gif"
        - "image/jpeg"
        - "image/png"
        - "image/png8"
        - "image/vnd.jpeg-png"
        - "image/vnd.jpeg-png8"

generated enum

public enum ImgFormat {
  
  LOL("lol"),
  
  IMAGE_GIF("image/gif"),
  
  IMAGE_JPEG("image/jpeg"),
  
  IMAGE_PNG("image/png"),
  
  IMAGE_PNG8("image/png8"),
  
  IMAGE_VND_JPEG_PNG("image/vnd.jpeg-png"),
  
  IMAGE_VND_JPEG_PNG8("image/vnd.jpeg-png8");

  private String value;

  ImgFormat(String value) {
    this.value = value;
  }

  @JsonValue
  public String getValue() {
    return value;
  }

  @Override
  public String toString() {
    return String.valueOf(value);
  }

  @JsonCreator
  public static ImgFormat fromValue(String value) {
    for (ImgFormat b : ImgFormat.values()) {
      if (b.value.equals(value)) {
        return b;
      }
    }
    throw new IllegalArgumentException("Unexpected value '" + value + "'");
  }
}

Resolved [org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'com.myapp.model.ImgFormat'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@javax.validation.constraints.NotNull @io.swagger.annotations.ApiParam @javax.validation.Valid @org.springframework.web.bind.annotation.RequestParam com.myapp.model.ImgFormat] for value 'image/png'; nested exception is java.lang.IllegalArgumentException: No enum constant com.myapp.model.ImgFormat.image/png]

Any news regarding this issue?

Not clear from the above if this is solved (I’m using 5.1.1 and still happening), but I found a simple enough way to get around it without needing to customise the enum templates.

Instead of defining the enum values only, add coressponding values under the x-enum-varnames as in the example below. This will overwrite the uppercase constant with the values you specify with no uppercase conversion. i.e.

DistributionType:
      type: string
      enum:
        - All
        - List
      x-enum-varnames:
        - All
        - List

Generates

public enum DistributionType {
  
  All("All"),
  
  List("List");

  private String value;

  DistributionType(String value) {
    this.value = value;
  }
...

Repetitive I know but preferable (for me anyway) to forcing everything to uppercase. Project I’m working on has a lot of configuration and properties identifiers in enums so retaining case sensitivity is essential.

Any updates here? A solution would be greatly appreciated.

Something seems to be wrong in Spring validation as the ENUMs are generated with correct lowercase value. Still values sent with lowercase fail with: java.lang.IllegalArgumentException: No enum constant name

Spring is not using the generated fromValue method (which works with lowercase) but instead Enum.valueOf(this.enumType, source.trim()) in StringToEnumConverterFactory.

public enum SortByEnum {
  
  NAME("name"),
  
  ID("id"),
  
  LASTUPDATEDTS("lastUpdatedTs");

  private String value;

  SortByEnum(String value) {
    this.value = value;
  }

  @JsonValue
  public String getValue() {
    return value;
  }

  @Override
  public String toString() {
    return String.valueOf(value);
  }

  @JsonCreator
  public static SortByEnum fromValue(String value) {
    for (SortByEnum b : SortByEnum.values()) {
      if (b.value.equals(value)) {
        return b;
      }
    }
    throw new IllegalArgumentException("Unexpected value '" + value + "'");
  }
}

This issue appears to have been fixed in v6.2.1 with #13349. Code generated by the current openapi-generator now produces 501 for /products?type=hardware.

I am not sure how that MR fixed anything @tkalliom. It doesn’t generate a converter to register to spring, it just shows what a converter would look like in the samples 🤔