当@ResponseBody 为空时覆盖默认消息

Question

我想从这个 Spring 类中覆盖这个行为：

public class RequestResponseBodyMethodProcessor extends AbstractMessageConverterMethodProcessor {
    ...
    @Override
    protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter parameter,
            Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
            ...
            if (arg == null && checkRequired(parameter)) {
                throw new HttpMessageNotReadableException("Required request body is missing: " +
                    parameter.getExecutable().toGenericString(), inputMessage);
            }
    ...
}

当@ReponseBody 来自@Controller 时，此方法处理错误。我试图让我自己的 CustomBodyMethodProcessor 从 RequestResponseBodyMethodProcessor 扩展，如下所示：

public class CustomBodyMethodProcessor extends RequestResponseBodyMethodProcessor {

    public CustomBodyMethodProcessor(List<HttpMessageConverter<?>> converters) {
        super(converters);
    }

    @Override
    protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter parameter,
                                                   Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {

        HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
        Assert.state(servletRequest != null, "No HttpServletRequest");
        ServletServerHttpRequest inputMessage = new ServletServerHttpRequest(servletRequest);

        Object arg = readWithMessageConverters(inputMessage, parameter, paramType);
        if (arg == null && checkRequired(parameter)) {
            //I want to change this....
            throw new HttpMessageNotReadableException("Required request body is missing: " +
                    parameter.getExecutable().toGenericString(), inputMessage);
        }
        return arg;
    }

}

所以，添加新的 CustomBodyMethodProcessor 我做了：

@Configuration
@EnableWebMvc
public class WebMvcConfig implements  WebMvcConfigurer {

    @Autowired
    List<HttpMessageConverter<?>> converters;


    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        WebMvcConfigurer.super.addArgumentResolvers(resolvers);
        resolvers.add(new CustomBodyMethodProcessor(converters));

    }

}

但这不起作用。当我调试时，总是在 RequestResponseBodyMethodProcessor 的 readWithMessageConverters 方法中停止，而不是在 CustomBodyMethodProcessor

的我的覆盖方法中停止

感谢您为我提供的任何帮助！

谢谢

Answer 1

找到了解决办法。

    @Autowired
    private RequestMappingHandlerAdapter adapter;

    @PostConstruct
    public void prioritizeCustomArgumentMethodHandlers () {
        List<HandlerMethodArgumentResolver> argumentResolvers = new ArrayList<>(adapter.getArgumentResolvers ());
        List<HandlerMethodArgumentResolver> customResolvers = adapter.getCustomArgumentResolvers();
        argumentResolvers.removeAll(customResolvers);
        argumentResolvers.addAll (0, customResolvers);
        adapter.setArgumentResolvers (argumentResolvers);
    }

我的 CustomBodyMethodProcessor 已添加到解析器列表中，但原始 RequestResponseBodyMethodProcessor 具有优先权，因此永远不会调用 CustomBodyMethodProcessor。

解决方案是从解析器中删除我的 CustomBodyMethodProcessor，给予优先权并再次将其添加到列表中！

感谢https://stackoverflow.com/a/19847526/4267653 和@BeUndead 提供线索！