Java Spring - 如何处理缺少的必需请求参数
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Java Spring - how to handle missing required request parameters
提问by peech
Consider the following mapping:
考虑以下映射：
@RequestMapping(value = "/superDuperPage", method = RequestMethod.GET)
public String superDuperPage(@RequestParam(value = "someParameter", required = true) String parameter)
{
return "somePage";
}
I want to handle the missing parameter case by notadding in required = false. By default, 400error is returned, but I want to return, let's say, a different page. How can I achieve this?
我想通过不添加required = false. 默认情况下，400会返回错误，但我想返回一个不同的页面。我怎样才能做到这一点？
采纳答案by Ali Dehghani
If a required @RequestParamis not present in the request, Spring will throw a MissingServletRequestParameterExceptionexception. You can define an @ExceptionHandlerin the same controller or in a @ControllerAdviceto handle that exception:
如果@RequestParam请求中不存在required ，Spring 将抛出MissingServletRequestParameterException异常。您可以@ExceptionHandler在同一个控制器或 a 中定义一个@ControllerAdvice来处理该异常：
@ExceptionHandler(MissingServletRequestParameterException.class)
public void handleMissingParams(MissingServletRequestParameterException ex) {
String name = ex.getParameterName();
System.out.println(name + " parameter is missing");
// Actual exception handling
}
I want to return let's say a different page. How to I achieve this?
我想返回让我们说一个不同的页面。我如何实现这一目标？
As the Spring documentationstates:
正如Spring 文档所述：
Much like standard controller methods annotated with a
@RequestMappingannotation, the method arguments and return values of@ExceptionHandlermethods can be flexible. For example, theHttpServletRequestcan be accessed in Servlet environments and thePortletRequestin Portlet environments. The return type can be aString, which is interpreted as a view name, aModelAndViewobject, aResponseEntity, or you can also add the@ResponseBodyto have the method return value converted with message converters and written to the response stream.
就像用
@RequestMapping注解注解的标准控制器方法一样，方法的参数和方法的返回值@ExceptionHandler可以是灵活的。例如，HttpServletRequest可以在 Servlet 环境和PortletRequestPortlet 环境中访问。返回类型可以是 aString，它被解释为视图名称、ModelAndView对象、 aResponseEntity，或者您也可以添加@ResponseBody以使方法返回值使用消息转换器转换并写入响应流。
回答by dimitrisli
You can do this with Spring 4.1onwards and Java 8by leveraging the Optionaltype. In your example that would mean your @RequestParamStringwill have now type of Optional<String>.
您可以通过利用Optional类型在Spring 4.1和Java 8之后执行此操作。在您的示例中，这意味着您的@RequestParam现在将具有.StringOptional<String>
Take a look at this articlefor an example showcasing this feature.
请查看本文以获取展示此功能的示例。
回答by Eric Giguere
An alternative
替代
If you use the @ControllerAdviceon your class and if it extends the Spring base class ResponseEntityExceptionHandler. A pre-defined function has been created on the base class for this purpose. You have to override it in your handler.
如果您在类上使用@ControllerAdvice并且它扩展了 Spring 基类ResponseEntityExceptionHandler。为此，在基类上创建了一个预定义的函数。您必须在处理程序中覆盖它。
@Override
protected ResponseEntity<Object> handleMissingServletRequestParameter(MissingServletRequestParameterException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
String name = ex.getParameterName();
logger.error(name + " parameter is missing");
return super.handleMissingServletRequestParameter(ex, headers, status, request);
}
This base class is very useful, especially if you want to process the validation errors that the framework creates.
这个基类非常有用，特别是如果您想处理框架创建的验证错误。
