SpringBoot响应处理之以Json数据返回的实现方法

@Controller
public class ResponseTestController {
    @ResponseBody // 标注 —— 自动返回json数据
    @GetMapping("/jsonTest")
    public Person testPerson(){
        Person person = new Person();
        person.setAge(20);
        person.setUserName("Liuwanqing");
        Pet pet = new Pet();
        pet.setName("huahua");
        pet.setAge("五个月");
        person.setPet(pet);
        return person;
    }
}

this.returnValueHandlers.handleReturnValue(returnValue, this.getReturnValueType(returnValue), mavContainer, webRequest);

HandlerMethodReturnValueHandler handler = this.selectHandler(returnValue, returnType);

   private HandlerMethodReturnValueHandler selectHandler(@Nullable Object value, MethodParameter returnType) {
        boolean isAsyncValue = this.isAsyncReturnValue(value, returnType);
        Iterator var4 = this.returnValueHandlers.iterator();
        HandlerMethodReturnValueHandler handler;
        do {
            do {
                if (!var4.hasNext()) {
                    return null;
                }
                handler = (HandlerMethodReturnValueHandler)var4.next();
            } while(isAsyncValue && !(handler instanceof AsyncHandlerMethodReturnValueHandler));
        } while(!handler.supportsReturnType(returnType));
        return handler;
    }

public interface HandlerMethodReturnValueHandler {
    boolean supportsReturnType(MethodParameter var1);
    void handleReturnValue(@Nullable Object var1, MethodParameter var2, ModelAndViewContainer var3, NativeWebRequest var4) throws Exception;
}

    public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
        mavContainer.setRequestHandled(true);
        ServletServerHttpRequest inputMessage = this.createInputMessage(webRequest);
        ServletServerHttpResponse outputMessage = this.createOutputMessage(webRequest);
        this.writeWithMessageConverters(returnValue, returnType, inputMessage, outputMessage);
    }

   protected List<MediaType> getProducibleMediaTypes(HttpServletRequest request, Class<?> valueClass, @Nullable Type targetType) {
        Set<MediaType> mediaTypes = (Set)request.getAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE);
        if (!CollectionUtils.isEmpty(mediaTypes)) {
            return new ArrayList(mediaTypes);
        } else if (this.allSupportedMediaTypes.isEmpty()) {
            return Collections.singletonList(MediaType.ALL);
        } else {
            List<MediaType> result = new ArrayList();
            Iterator var6 = this.messageConverters.iterator();
            while(true) {
                while(var6.hasNext()) {
                    HttpMessageConverter<?> converter = (HttpMessageConverter)var6.next();
                    if (converter instanceof GenericHttpMessageConverter && targetType != null) {
                        if (((GenericHttpMessageConverter)converter).canWrite(targetType, valueClass, (MediaType)null)) {
                            result.addAll(converter.getSupportedMediaTypes());
                        }
                    } else if (converter.canWrite(valueClass, (MediaType)null)) {
                        result.addAll(converter.getSupportedMediaTypes());
                    }
                }
                return result;
            }
        }
    }