java - HttpMediaTypeNotAcceptableException : Could not find acceptable representation in exceptionhandler

Question

我的 Controller 中有以下图片下载方法(Spring 4.1):

@RequestMapping(value = "/get/image/{id}/{fileName}", method=RequestMethod.GET)
public @ResponseBody byte[] showImageOnId(@PathVariable("id") String id, @PathVariable("fileName") String fileName) {
    setContentType(fileName); //sets contenttype based on extention of file
    return getImage(id, fileName);
}

以下ControllerAdvice方法应该处理一个不存在的文件并返回一个 json 错误响应:

@ExceptionHandler(ResourceNotFoundException.class)
@ResponseStatus(HttpStatus.NOT_FOUND)
public @ResponseBody Map<String, String> handleResourceNotFoundException(ResourceNotFoundException e) {
    Map<String, String> errorMap = new HashMap<String, String>();
    errorMap.put("error", e.getMessage());
    return errorMap;
}

我的 JUnit 测试完美无缺

(EDIT这是因为扩展名.bla:这也适用于appserver):

@Test
public void testResourceNotFound() throws Exception {
    String fileName = "bla.bla";
      mvc.perform(MockMvcRequestBuilders.get("/get/image/bla/" + fileName)
            .with(httpBasic("test", "test")))
            .andDo(print())
            .andExpect(jsonPath("$error").value(Matchers.startsWith("Resource not found")))
            .andExpect(status().is(404));
}

并给出以下输出:

MockHttpServletResponse:
          Status = 404
   Error message = null
         Headers = {X-Content-Type-Options=[nosniff], X-XSS-Protection=[1; mode=block], Cache-Control=[no-cache, no-store, max-age=0, must-revalidate], Pragma=[no-cache], Expires=[0], X-Frame-Options=[DENY], Content-Type=[application/json]}
    Content type = application/json
            Body = {"error":"Resource not found: bla/bla.bla"}
   Forwarded URL = null
  Redirected URL = null
         Cookies = []

但是，在我的应用服务器上，当我尝试下载不存在的图像时收到以下错误消息:

(编辑这是因为扩展 .jpg :这在带有 .jpg 扩展的 JUnit 测试中也失败):

ERROR org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver - Failed to invoke @ExceptionHandler method: public java.util.Map<java.lang.String, java.lang.String> nl.krocket.ocr.web.controller.ExceptionController.handleResourceNotFoundException(nl.krocket.ocr.web.backing.ResourceNotFoundException)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation

我在我的 mvc 配置中配置了 messageconverters，如下所示:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters.add(mappingJackson2HttpMessageConverter());
    converters.add(byteArrayHttpMessageConverter());
}

@Bean
public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    //objectMapper.registerModule(new JSR310Module());
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
    converter.setObjectMapper(objectMapper);
    converter.setSupportedMediaTypes(getJsonMediaTypes());
    return converter;
}

@Bean
public ByteArrayHttpMessageConverter byteArrayHttpMessageConverter() {
    ByteArrayHttpMessageConverter arrayHttpMessageConverter = new ByteArrayHttpMessageConverter();
    arrayHttpMessageConverter.setSupportedMediaTypes(getImageMediaTypes());
    return arrayHttpMessageConverter;
}

我错过了什么？为什么 JUnit 测试有效？

Answer 1

您需要决定 Spring 应如何确定响应的媒体类型。这可以通过多种方式完成:

• 路径扩展名(例如/image.jpg)
• 网址参数(例如 ?format=jpg)
• HTTP Accept header (例如，Accept: image/jpg)

默认情况下，Spring 查看 extension 而不是 Accept header 。如果您实现扩展 WebMvcConfigurerAdapter 的 @Configuration 类，则可以更改此行为。 (或者从 Spring 5.0 开始，只需实现 WebMvcConfigurer 。在那里您可以覆盖 configureContentNegotiation(ContentNegotiationConfigurer configurer) 并根据您的需要配置 ContentNegotiationConfigurer，例如，通过调用

ContentNegotiationConfigurer#favorParameter
ContentNegotiationConfigurer#favorPathExtension

如果您将两者都设置为 false，那么 Spring 将查看 Accept header 。由于您的客户端可以说 Accept: image/*,application/json 并处理两者，因此 Spring 应该能够返回图像或错误 JSON。

见 this Spring tutorial有关更多信息和示例的内容协商。