Spring的@RequestParam与Enum

Question

我有这个枚举：

public enum SortEnum {
    asc, desc;
}

我想用作休息请求的参数：

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

我发送这些请求时工作正常

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

但是当我发送时：

/events?sort=somethingElse

我在控制台中得到500响应和此消息：

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

有没有办法阻止spring抛出这些异常并将枚举设置为null？

编辑

Strelok接受的答案有效。但是，我决定处理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

您可以创建一个自定义转换器，它将在提供无效值时返回null而不是异常。

像这样的东西：

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

一个简单的转换器可能看起来像这样：

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 2

你需要做以下事情

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

请参阅以下内容：https://machiel.me/post/java-enums-as-request-parameters-in-spring-4/

Answer 3

如果你使用的是Spring Boot，this is the reason你不应该使用WebMvcConfigurationSupport。

最佳实践，您应该实现接口org.springframework.core.convert.converter.Converter，并使用注释@Component。然后Spring Boot将自动加载所有Converter的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 4

到目前为止提供的答案并不完整。这是一个循序渐进的答案示例，对我有用： -

1st在端点签名中定义枚举（订阅类型）。 例：

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,

第2步定义将用于从String转换为枚举的自定义属性编辑器：

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);
        }
    }
}

3向控制器注册属性编辑器：

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

从字符串到枚举的翻译现在应该完美地发生。

Answer 5

你可以使用String而不是SortEnum param

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

并使用转换它

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

在getEvents（...）端点方法内部失去了优雅，但获得了对转换和可能的错误处理的更多控制。