assertTrue(this.handlerMapping.useSuffixPatternMatch());
assertFalse(this.handlerMapping.useRegisteredSuffixPatternMatch());
Map<String, MediaType> fileExtensions = Collections.singletonMap("json", MediaType.APPLICATION_JSON);
PathExtensionContentNegotiationStrategy strategy = new PathExtensionContentNegotiationStrategy(fileExtensions);
ContentNegotiationManager manager = new ContentNegotiationManager(strategy);
this.handlerMapping.setContentNegotiationManager(manager);
this.handlerMapping.setUseRegisteredSuffixPatternMatch(true);
this.handlerMapping.afterPropertiesSet();