SpringMVC MethodArgumentResolver的作用与实现

public class MyReturnValueHandler implements MethodReturnValueHandler {
    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        return returnType.getParameterType().equals(MyData.class);
    }
    @Override
    public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
        MyData myData = (MyData) returnValue;
        // do something with myData
        HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
        response.getWriter().write("hello world");
    }
}

public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter {
    private final List<MethodReturnValueHandler> returnValueHandlers = new ArrayList<>();
    @Override
    public void afterPropertiesSet() {
        super.afterPropertiesSet();
        this.returnValueHandlers.add(new MyReturnValueHandler());
    }
    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        for (MethodReturnValueHandler handler : this.returnValueHandlers) {
            if (handler.supportsReturnType(returnType)) {
                return true;
            }
        }
        return false;
    }
    @Override
    protected ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
        Object returnValue = handlerMethod.getMethod().invoke(handlerMethod.getBean(), handlerMethod.getMethodParameters());
        MethodParameter returnType = handlerMethod.getReturnType();
        for (MethodReturnValueHandler handler : this.returnValueHandlers) {
            if (handler.supportsReturnType(returnType)) {
                ModelAndViewContainer mavContainer = new ModelAndViewContainer();
                handler.handleReturnValue(returnValue, returnType, mavContainer, new ServletWebRequest(request, response));
                return mavContainer.getModelAndView();
            }
        }
        return null;
    }
}