网关和中心统一异常

　　背景
　　后端提供的服务，都是需要统一格式的，比如都需要返回错误码，错误信息，全局流水等等。那么在后端系统中，如果抛了异常不处理的话，这些格式就没法控制，今天讲讲springCloudGateway和springboot服务怎么在抛异常的时候，统一格式。springCloudGateway网关
　　网关分为限流异常和业务异常限流异常
　　网关有限流的功能，那么在限流的时候，需要对返回做处理（这里用的sentinel做的限流）
　　首先我们有个配置类@Configuration public class SentinelException {    private final List viewResolvers;   private final ServerCodecConfigurer serverCodecConfigurer;    public SentinelException(ObjectProvider> viewResolversProvider,       ServerCodecConfigurer serverCodecConfigurer) {     this.viewResolvers = viewResolversProvider.getIfAvailable(Collections::emptyList);     this.serverCodecConfigurer = serverCodecConfigurer;   }    @Bean   @Order(Ordered.HIGHEST_PRECEDENCE)   public SentinelGatewayBlockExceptionHandler sentinelGatewayBlockExceptionHandler() {     return new SentinelGatewayExceptionHandler(viewResolvers, serverCodecConfigurer);   }    @Bean   @Order(Ordered.HIGHEST_PRECEDENCE)   public GlobalFilter sentinelGatewayFilter() {     return new SentinelGatewayFilter();   } }
　　然后新建一个SentinelGatewayExceptionHandler类继承SentinelGatewayBlockExceptionHandler，重写handle方法@Slf4j public class SentinelGatewayExceptionHandler extends SentinelGatewayBlockExceptionHandler {    private List viewResolvers;   private List> messageWriters;    public SentinelGatewayExceptionHandler(List viewResolvers,       ServerCodecConfigurer serverCodecConfigurer) {     super(viewResolvers, serverCodecConfigurer);     this.viewResolvers = viewResolvers;     this.messageWriters = serverCodecConfigurer.getWriters();   }    @Override   public Mono handle(ServerWebExchange serverWebExchange, Throwable throwable) {      if (serverWebExchange.getResponse().isCommitted()) {       return Mono.error(throwable);     }     if (!BlockException.isBlockException(throwable)) {       return Mono.error(throwable);     }     return handleBlockedRequest(serverWebExchange, throwable)         .flatMap(response -> writeResponse(response, serverWebExchange));   }    private Mono handleBlockedRequest(ServerWebExchange exchange,       Throwable throwable) {     return GatewayCallbackManager.getBlockHandler().handleRequest(exchange, throwable);   }    private final Supplier contextSupplier = () -> new ServerResponse.Context() {     @Override     public List> messageWriters() {       return SentinelGatewayExceptionHandler.this.messageWriters;     }      @Override     public List viewResolvers() {       return SentinelGatewayExceptionHandler.this.viewResolvers;     }   };    private Mono writeResponse(ServerResponse response, ServerWebExchange exchange) {     MDC.clear();     log.error(＂交易【{}】在【{}】时间被限制，请检查是否有大流量进入＂,         exchange.getRequest().getPath(),         DateUtil.format(new Date(), CakeConstants.FORMAT_TIME));     ServerHttpResponse resp = exchange.getResponse();     resp.getHeaders().add(＂Content-Type＂, ＂application/json;charset=UTF-8＂);     Map map = new HashMap();          String json = JSON.toJSONString(map, CakeConstants.FORMAT_TIME);     DataBuffer buffer = resp.bufferFactory().wrap(json.getBytes(StandardCharsets.UTF_8));     return resp.writeWith(Mono.just(buffer));   }
　　Map map = new HashMap();这里的map就是定义的返回格式，随便自己定义，返回的json数据。业务异常
　　网关可能发生业务异常，那么我们也要做处理。新建一个GlobalErrorWebExceptionHandler类，实现ErrorWebExceptionHandler接口，重写handle方法，这里我就不贴所有代码了。@Slf4j @Order(-1) @Configuration @RequiredArgsConstructor(onConstructor = @__(@Autowired)) public class GlobalErrorWebExceptionHandler implements ErrorWebExceptionHandler {      @SneakyThrows   @Override   public Mono handle(ServerWebExchange exchange, Throwable ex) {     ServerHttpResponse response = exchange.getResponse();       response.getHeaders().setContentType(MediaType.APPLICATION_JSON);       return response.writeWith(Mono.fromSupplier(() -> {         DataBufferFactory bufferFactory = response.bufferFactory();         try {           return bufferFactory.wrap(mapper.writeValueAsBytes(＂返回数据，自定义＂));         } catch (Exception e) {           log.info(＂返回失败＂);           return bufferFactory.wrap(JSON.toJSONBytes(＂返回数据，自定义＂));         }       }));   }springboot服务
　　springboot分为流控异常，业务异常，还有404这些。流控异常
　　新建一个SentinelBootException类，实现BlockExceptionHandler，重写handle方法@Slf4j @Component public class SentinelBootException implements BlockExceptionHandler {    @Override   public void handle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse,       BlockException e) throws Exception {     MDC.clear();     CenterQueryResponse responseData = new CenterQueryResponse();          httpServletResponse.setStatus(200);     httpServletResponse.setContentType(＂application/json;charset=utf-8＂);     PrintWriter out = httpServletResponse.getWriter();     out.print(JSON.toJSONString(responseData, CakeConstants.FORMAT_TIME));     out.flush();     out.close();   } }
　　responseData对象就是自定义返回的数据，大家按照自己项目的定义就行。404等处理
　　新建TransferNotFindController类，实现ErrorController接口，对/error路径进行处理。@RestController public class TransferNotFindController implements ErrorController {    private static final Logger log = LoggerFactory.getLogger(TransferNotFindController.class);    /**    * 默认错误    */   private static final String path_default = ＂/error＂;    @RequestMapping(value = path_default, produces = {MediaType.APPLICATION_JSON_VALUE})   public CenterQueryResponse handleError(HttpServletRequest request) {     CenterQueryResponse responseData = new CenterQueryResponse();          log.info(＂交易不存在[{}]＂, JSON.toJSONString(responseData, CakeConstants.FORMAT_TIME));     return responseData;   } }
　　CenterQueryResponse对象就是返回的数据。大家根据项目自行定义。业务异常
　　这部分比较麻烦，我是有对controller成做AOP切面处理的，我用了try catch做了一些异常处理，这部分就不写了，大家可以自己去处理，在catch里面对异常处理。还有一部分是全局异常处理，利用的是@ControllerAdvice注解和@ExceptionHandler注解。先定义一个异常类PgException继承RuntimeException。@Data @NoArgsConstructor @AllArgsConstructor public class PgException extends RuntimeException {    private String code;   private String msg;    public PgException(String code, String msg) {     this.code = code;     this.msg = msg;   }    @Override   public String getMessage() {     return this.msg;   }    @Override   public String toString() {     return ＂Exception(code=＂ + this.getCode() + ＂, message=＂ + this.getMsg() + ＂)＂;   }  }
　　这里面有个地方注意一下，重写了getMessage，为什么要重写，因为在日志里你不重写的话，那么异常信息打印出来都是null，重写了，你打印的异常信息就是你的错误信息。
　　然后新建PgExceptionHandler类，这里的代码没完整贴出来。@Slf4j @ControllerAdvice public class PgExceptionHandler {    @ExceptionHandler(PgException.class)   @ResponseBody   public CenterCommandResponse handlePgException(PgException ex) {     CenterCommandResponse centerCommandResponse = new CenterCommandResponse();          RequestContext.remove();     return centerCommandResponse;   }    @ExceptionHandler(Exception.class)   @ResponseBody   public CenterCommandResponse handleException(Exception ex) {     CenterCommandResponse centerCommandResponse = new CenterCommandResponse(); 		…         return centerCommandResponse;   } }
　　CenterCommandResponse就是要返回的数据，大家可以根据项目自行定义。
　　网关和服务应用的异常处理就到这了，基本包含了当前所有的异常场景了，后续还有别的再加吧。再贴个我的异常返回图。
　　异常返回信息