Spring's @RequestParam with Enum

Question

I have this enum :

public enum SortEnum {
    asc, desc;
}

That I want to use as a parameter of a rest request :

@RequestMapping(value = "/events", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public List<Event> getEvents(@RequestParam(name = "sort", required = false) SortEnum sort) {

It works fine when I send these requests

/events 
/events?sort=asc
/events?sort=desc

But when I send :

/events?sort=somethingElse

I get a 500 response and this message in the console :

2016-09-29 17:20:51.600 DEBUG 5104 --- [  XNIO-2 task-6] com.myApp.aop.logging.LoggingAspect   : Enter: com.myApp.web.rest.errors.ExceptionTranslator.processRuntimeException() with argument[s] = [org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type [java.lang.String] to required type [com.myApp.common.SortEnum]; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.RequestParam com.myApp.common.SortEnum] for value 'somethingElse'; nested exception is java.lang.IllegalArgumentException: No enum constant com.myApp.common.SortEnum.somethingElse]
2016-09-29 17:20:51.600 DEBUG 5104 --- [  XNIO-2 task-6] com.myApp.aop.logging.LoggingAspect   : Exit: com.myApp.web.rest.errors.ExceptionTranslator.processRuntimeException() with result = <500 Internal Server Error,com.myApp.web.rest.errors.ErrorVM@1e3343c9,{}>
2016-09-29 17:20:51.601  WARN 5104 --- [  XNIO-2 task-6] .m.m.a.ExceptionHandlerExceptionResolver : Resolved exception caused by Handler execution: org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type [java.lang.String] to required type [com.myApp.common.SortEnum]; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.RequestParam com.myApp.common.SortEnum] for value 'somethingElse'; nested exception is java.lang.IllegalArgumentException: No enum constant com.myApp.common.SortEnum.somethingElse

Is there a way to prevent spring from throwing these exceptions and set the enum to null ?

EDIT

The Strelok's accepted answer works. However, I decided to deal with handling the MethodArgumentTypeMismatchException.

@ControllerAdvice
public class ExceptionTranslator {

    @ExceptionHandler(MethodArgumentTypeMismatchException.class)
    @ResponseBody
    public ResponseEntity<Object> handleMethodArgumentTypeMismatchException(MethodArgumentTypeMismatchException e) {
        Class<?> type = e.getRequiredType();
        String message;
        if(type.isEnum()){
            message = "The parameter " + e.getName() + " must have a value among : " + StringUtils.join(type.getEnumConstants(), ", ");
        }
        else{
            message = "The parameter " + e.getName() + " must be of type " + type.getTypeName();
        }
        return buildResponse(HttpStatus.UNPROCESSABLE_ENTITY, message);
    }

Answer 1

you can use String instead of SortEnum param

@RequestParam(name = "sort", required = false) String sort

and convert it using

SortEnum se;
try {
   se = SortEnum.valueOf(source);
} catch(IllegalArgumentException e) {
   se = null;
}

inside of getEvents(...) endpoint method losing elegance but gaining more control over conversion and possible error handling.

Answer 2

If you are using Spring Boot, this is the reason that you should not use WebMvcConfigurationSupport.

The best practice, you should implement interface org.springframework.core.convert.converter.Converter, and with annotation @Component. Then Spring Boot will auto load all Converter's bean. Spring Boot code

@Component
public class GenderEnumConverter implements Converter<String, GenderEnum> {
    @Override
    public GenderEnum convert(String value) {
        return GenderEnum.of(Integer.valueOf(value));
    }
}

Demo Project

Answer 3

You can create a custom converter that will return null instead of an exception when an invalid value is supplied.

Something like this:

@Configuration
public class MyConfig extends WebMvcConfigurationSupport {
   @Override
   public FormattingConversionService mvcConversionService() {
       FormattingConversionService f = super.mvcConversionService();
       f.addConverter(new MyCustomEnumConverter());
       return f;
   }
}

And a simple converter might look like this:

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
       }
    }
}

Answer 4

you need to do the following

@InitBinder
public void initBinder(WebDataBinder dataBinder) {
    dataBinder.registerCustomEditor(YourEnum.class, new YourEnumConverter());
}

refer the following : https://machiel.me/post/java-enums-as-request-parameters-in-spring-4/

Answer 5

The answers provided so far are not complete. Here is an answer example step-by-step that worked for me:-

1st Define the enum in your endpoint signature(subscription type).
Example:

public ResponseEntity v1_getSubscriptions(@PathVariable String agencyCode,
                                          @RequestParam(value = "uwcompany", required = false) String uwCompany,
                                          @RequestParam(value = "subscriptiontype", required = false) SubscriptionType subscriptionType,
                                          @RequestParam(value = "alert", required = false) String alert,

2nd Define a custom property editor that will be used to translate from String to enum:

import java.beans.PropertyEditorSupport;

public class SubscriptionTypeEditor extends PropertyEditorSupport {

    public void setAsText(String text) {
        try {
            setValue(SubscriptionType.valueOf(text.toUpperCase()));
        } catch (Exception ex) {
            setValue(null);
        }
    }
}

3rd Register the property editor with the controller:

@InitBinder ("subscriptiontype")
public void initBinder(WebDataBinder dataBinder) {
    dataBinder.registerCustomEditor(SubscriptionType.class, new SubscriptionTypeEditor());
}

Translations from string to enum should happen perfectly now.

Answer 6

If you are already implementing WebMvcConfigurer, instead of WebMvcConfigurationSupport, you can add new converter by implementing the method addFormatters

  @Override
  public void addFormatters(FormatterRegistry registry) {
    registry.addConverter(new MyCustomEnumConverter());
  }