因Spring Cloud Gateway作为网关是异步的因此日志记录很重要，下面异常类是我再工作中长期使用的

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/**
 * @version 2019/8/14
 * @description: 异常拦截器
 * @modified:
 */
@Slf4j
public class JsonExceptionHandler implements ErrorWebExceptionHandler {
 
    /**
     * MessageReader
     */
    private List<HttpMessageReader<?>> messageReaders = Collections.emptyList();
 
    /**
     * MessageWriter
     */
    private List<HttpMessageWriter<?>> messageWriters = Collections.emptyList();
 
    /**
     * ViewResolvers
     */
    private List<ViewResolver> viewResolvers = Collections.emptyList();
 
    /**
     * 存储处理异常后的信息
     */
    private ThreadLocal<ResEntity> exceptionHandlerResult = new ThreadLocal<>();
 
    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    public void setMessageReaders(List<HttpMessageReader<?>> messageReaders) {
        Assert.notNull(messageReaders, "'messageReaders' must not be null");
        this.messageReaders = messageReaders;
    }
 
    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    public void setViewResolvers(List<ViewResolver> viewResolvers) {
        this.viewResolvers = viewResolvers;
    }
 
    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    public void setMessageWriters(List<HttpMessageWriter<?>> messageWriters) {
        Assert.notNull(messageWriters, "'messageWriters' must not be null");
        this.messageWriters = messageWriters;
    }
 
    @Override
    public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
        // 按照异常类型进行处理 默认500
　　　　　　int httpStatus = HttpStatus.INTERNAL_SERVER_ERROR.value();
　　　　　　String body = "系统异常，请联系管理员";
　　　　　　if (ex instanceof NotFoundException) {
    　　　　　　httpStatus = HttpStatus.NOT_FOUND.value();
   　　　　　　 body = ex.getMessage();
　　　　　　}else if(ex instanceof ResponseStatusException){
    　　　　　　ResponseStatusException responseStatusException = (ResponseStatusException) ex;
    　　　　　　httpStatus = responseStatusException.getStatus().value();
    　　　　　　body = responseStatusException.getMessage();
　　　　　　} else if (ex instanceof BusinessException) {
    　　　　　　body  = ex.getMessage();
    　　　　　　httpStatus = ((BusinessException) ex).toResEntity().getHttpStatus();
　　　　　　} else if (ex instanceof RuntimeException) {
    　　　　　　Throwable cause = ex.getCause();
   　　　　　　 body  = ex.getMessage();
    　　　　　　if(null != cause && cause.getMessage().contains("Load balancer does not have available server for client")){
       　　　　　　 body = "服务不存在";
   　　　　　　 }
　　　　　　}
　　　　　　//错误记录
        ServerHttpRequest request = exchange.getRequest();
        log.error("[全局异常处理]异常请求路径:{}", request.getPath());
        log.error("异常详细信息：{}",ex);
        //封装响应体
        ResEntity res = new ResEntity();
        res.setHttpStatus(httpStatus);
        res.setMsg(body);
 
        //参考AbstractErrorWebExceptionHandler
        if (exchange.getResponse().isCommitted()) {
            return Mono.error(ex);
        }
        exceptionHandlerResult.set(res);
        ServerRequest newRequest = ServerRequest.create(exchange, this.messageReaders);
        return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse).route(newRequest)
                .switchIfEmpty(Mono.error(ex))
                .flatMap((handler) -> handler.handle(newRequest))
                .flatMap((response) -> write(exchange, response));
 
    }
 
    /**
     * 参考DefaultErrorWebExceptionHandler
     */
    protected Mono<ServerResponse> renderErrorResponse(ServerRequest request) {
        ResEntity result = exceptionHandlerResult.get();
 
        //404 因前端框架问题，不转换处理 ，因此目前只有系统报500才转换为自定义的状态码
        if(HttpStatus.INTERNAL_SERVER_ERROR.value() == result.getHttpStatus()){
            return ServerResponse.status(HttpStatus.OK.value())
                    .contentType(MediaType.APPLICATION_JSON_UTF8)
                    .body(BodyInserters.fromObject(result));
        }
        return ServerResponse.status(result.getHttpStatus())
                .contentType(MediaType.APPLICATION_JSON_UTF8)
                .body(BodyInserters.fromObject(result));
    }
 
    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    private Mono<? extends Void> write(ServerWebExchange exchange,
                                       ServerResponse response) {
        exchange.getResponse().getHeaders()
                .setContentType(response.headers().getContentType());
        return response.writeTo(exchange, new ResponseContext());
    }
 
    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    private class ResponseContext implements ServerResponse.Context {
 
        @Override
        public List<HttpMessageWriter<?>> messageWriters() {
            return JsonExceptionHandler.this.messageWriters;
        }
 
        @Override
        public List<ViewResolver> viewResolvers() {
            return JsonExceptionHandler.this.viewResolvers;
        }
    }
}

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