31. 自定义 HandlerExceptionResolver

前言

Springmvc 中 异常解析器的默认实现有 ExceptionHandlerExceptionResolver、ResponseStatusExceptionResolver 和 DefaultHandlerExceptionResolver 等，都实现同一的接口 HandlerExceptionResolver。

一、HandlerExceptionResolver

接口中只有一个解析异常的方法

public interface HandlerExceptionResolver {


	@Nullable
	ModelAndView resolveException(
			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex);

}

二、自定义 HandlerExceptionResolver

public class CustomHandlerExceptionResolver implements HandlerExceptionResolver {


    private static String msg = "服务器错误";

    @Override
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {


        if (e instanceof RuntimeException) {


            ModelAndView modelAndView = new ModelAndView(new MappingJackson2JsonView());
            modelAndView.addObject("message", e.getMessage());
            modelAndView.addObject("code", 500);
            return modelAndView;
        } else {


            return null;
        }
    }
}

三、注册

@Configuration
public class HandlerExceptionResolverConfig implements WebMvcConfigurer {



    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {


		//注册自定义异常解析器
        resolvers.add(new CustomHandlerExceptionResolver());

    }

}

注意，如果注册了自定义的异常解析器，则默认的异常解析器就不会生效了，像全局异常处理 @ControllerAdvice 就失效了，在源码中是这样的：

@Bean
	public HandlerExceptionResolver handlerExceptionResolver(
			@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager) {


		List<HandlerExceptionResolver> exceptionResolvers = new ArrayList<>();
		//加载自定义异常解析器
		configureHandlerExceptionResolvers(exceptionResolvers);
		if (exceptionResolvers.isEmpty()) {


			//没有自定义异常解析器，才会进入这里，将默认的异常解析器加载进来
			addDefaultHandlerExceptionResolvers(exceptionResolvers, contentNegotiationManager);
		}

		//扩展异常解析器
		extendHandlerExceptionResolvers(exceptionResolvers);
		HandlerExceptionResolverComposite composite = new HandlerExceptionResolverComposite();
		composite.setOrder(0);
		composite.setExceptionResolvers(exceptionResolvers);
		return composite;
	}