Spring cloud gateway的自定义异常响应

由于gateway默认的返回码和返回信息不能满足下游微服务的自定义的异常响应码和描述，则需要通过网关透传下游微服务的异常的码值或者至少异常描述信息。

spring cloud gateway给我们留了口子，只需要继承类DefaultErrorWebExceptionHandler，并覆盖相应的接口，并且声明ErrorWebExceptionHandler配置即可，下面贴出代码:

1、 ErrorWebExceptionHandler配置

@Configuration
@EnableConfigurationProperties({
    
    ServerProperties.class, ResourceProperties.class})
public class ExceptionHandlerConfiguration {
    
    

    private final ServerProperties serverProperties;

    private final ApplicationContext applicationContext;

    private final ResourceProperties resourceProperties;

    private final List<ViewResolver> viewResolvers;

    private final ServerCodecConfigurer serverCodecConfigurer;

    public ExceptionHandlerConfiguration(ServerProperties serverProperties,
                                         ResourceProperties resourceProperties,
                                         ObjectProvider<List<ViewResolver>> viewResolversProvider,
                                         ServerCodecConfigurer serverCodecConfigurer,
                                         ApplicationContext applicationContext) {
    
    
        this.serverProperties = serverProperties;
        this.applicationContext = applicationContext;
        this.resourceProperties = resourceProperties;
        this.viewResolvers = viewResolversProvider.getIfAvailable(Collections::emptyList);
        this.serverCodecConfigurer = serverCodecConfigurer;
    }

    @Bean
    @Order(Ordered.HIGHEST_PRECEDENCE)
    public ErrorWebExceptionHandler errorWebExceptionHandler(ErrorAttributes errorAttributes) {
    
    
        JsonExceptionHandler exceptionHandler = new JsonExceptionHandler(
                errorAttributes,
                this.resourceProperties,
                this.serverProperties.getError(),
                this.applicationContext);
        exceptionHandler.setViewResolvers(this.viewResolvers);
        exceptionHandler.setMessageWriters(this.serverCodecConfigurer.getWriters());
        exceptionHandler.setMessageReaders(this.serverCodecConfigurer.getReaders());
        return exceptionHandler;
    }

}

2、自定义DefaultErrorWebExceptionHandler异常处理类

public class JsonExceptionHandler extends DefaultErrorWebExceptionHandler {
    
    

    private static Logger logger = LoggerFactory.getLogger(JsonExceptionHandler.class);

    public JsonExceptionHandler(ErrorAttributes errorAttributes, ResourceProperties resourceProperties,
                                ErrorProperties errorProperties, ApplicationContext applicationContext) {
    
    
        super(errorAttributes, resourceProperties, errorProperties, applicationContext);
    }

    /**
     * 获取异常属性
     */
    @Override
    protected Map<String, Object> getErrorAttributes(ServerRequest request, boolean includeStackTrace) {
    
    
        int code = HttpStatus.INTERNAL_SERVER_ERROR.value();
        Throwable error = super.getError(request);
        if (error instanceof org.springframework.cloud.gateway.support.NotFoundException) {
    
    
            code = HttpStatus.NOT_FOUND.value();
        }
//        return response(code, this.buildMessage(request, error));
        return response(code, error.getMessage());
    }

    /**
     * 指定响应处理方法为JSON处理的方法
     * @param errorAttributes
     */
    @Override
    protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
    
    
        return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse);
    }


    /**
     * 根据code获取对应的HttpStatus
     * @param errorAttributes
     */
    @Override
    protected int getHttpStatus(Map<String, Object> errorAttributes) {
    
    
        int statusCode = (int) errorAttributes.get("code");
//        return HttpStatus.valueOf(statusCode);
        return statusCode;
    }

    /**
     * 构建异常信息
     * @param request
     * @param ex
     * @return
     */
    private String buildMessage(ServerRequest request, Throwable ex) {
    
    
        StringBuilder message = new StringBuilder("Failed to handle request [");
        message.append(request.methodName());
        message.append(" ");
        message.append(request.uri());
        message.append("]");
        if (ex != null) {
    
    
            message.append(": ");
            message.append(ex.getMessage());
        }
        return message.toString();
    }

    /**
     * 构建返回的JSON数据格式
     * @param status        状态码
     * @param errorMessage  异常信息
     * @return
     */
    public static Map<String, Object> response(int status, String errorMessage) {
    
    
        Map<String, Object> map = new HashMap<>();
        map.put("code", status);
        map.put("message", errorMessage);
        map.put("data", null);
        logger.error(map.toString());
        return map;
    }
}