Spring如何與枚舉

Question

@RequestParam我有這樣的枚舉：

public enum SortEnum { 
    asc, desc; 
} 

那我想作爲一個休息的請求的參數使用方法：

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

它正常工作，當我把這些請求

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

但是當我發送：

/events?sort=somethingElse 

我得到在控制檯500響應這個消息：

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 

有沒有一種方法，以防止從春天拋出這些異常，並設置枚舉爲空？

編輯

的Strelok的接受的答案作品。但是，我決定處理處理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

您可以創建一個自定義轉換器時，提供了無效值將返回null而不是例外。

事情是這樣的：

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

和一個簡單的轉換器可能是這樣的：

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

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

參閱以下內容：https://machiel.me/post/java-enums-as-request-parameters-in-spring-4/