##序 使用zuul作为api网关的话，经常会碰见一些异常，这里小结一下。

##ZuulException 这个是最外层的异常

public class ZuulException extends Exception {public int nStatusCode;public String errorCause;/*** Source Throwable, message, status code and info about the cause* @param throwable* @param sMessage* @param nStatusCode* @param errorCause*/public ZuulException(Throwable throwable, String sMessage, int nStatusCode, String errorCause) {super(sMessage, throwable);this.nStatusCode = nStatusCode;this.errorCause = errorCause;incrementCounter("ZUUL::EXCEPTION:" + errorCause + ":" + nStatusCode);}/*** error message, status code and info about the cause* @param sMessage* @param nStatusCode* @param errorCause*/public ZuulException(String sMessage, int nStatusCode, String errorCause) {super(sMessage);this.nStatusCode = nStatusCode;this.errorCause = errorCause;incrementCounter("ZUUL::EXCEPTION:" + errorCause + ":" + nStatusCode);}/*** Source Throwable,  status code and info about the cause* @param throwable* @param nStatusCode* @param errorCause*/public ZuulException(Throwable throwable, int nStatusCode, String errorCause) {super(throwable.getMessage(), throwable);this.nStatusCode = nStatusCode;this.errorCause = errorCause;incrementCounter("ZUUL::EXCEPTION:" + errorCause + ":" + nStatusCode);}private static final void incrementCounter(String name) {CounterFactory.instance().increment(name);}}

##RibbonRoutingFilter spring-cloud-netflix-core-1.2.6.RELEASE-sources.jar!/org/springframework/cloud/netflix/zuul/filters/route/RibbonRoutingFilter.java 这个类抛了很多ZuulException：

@Overridepublic Object run() {RequestContext context = RequestContext.getCurrentContext();this.helper.addIgnoredHeaders();try {RibbonCommandContext commandContext = buildCommandContext(context);ClientHttpResponse response = forward(commandContext);setResponse(response);return response;}catch (ZuulException ex) {context.set(ERROR_STATUS_CODE, ex.nStatusCode);context.set("error.message", ex.errorCause);context.set("error.exception", ex);}catch (Exception ex) {context.set("error.status_code",HttpServletResponse.SC_INTERNAL_SERVER_ERROR);context.set("error.exception", ex);}return null;}

###forward

protected ClientHttpResponse forward(RibbonCommandContext context) throws Exception {Map<String, Object> info = this.helper.debug(context.getMethod(),context.getUri(), context.getHeaders(), context.getParams(),context.getRequestEntity());RibbonCommand command = this.ribbonCommandFactory.create(context);try {ClientHttpResponse response = command.execute();this.helper.appendDebug(info, response.getStatusCode().value(),response.getHeaders());return response;}catch (HystrixRuntimeException ex) {return handleException(info, ex);}}

这里有一个HystrixRuntimeException，主要是跟hystrix相关的，比如超时等。 ###handleException

protected ClientHttpResponse handleException(Map<String, Object> info,HystrixRuntimeException ex) throws ZuulException {int statusCode = HttpStatus.INTERNAL_SERVER_ERROR.value();Throwable cause = ex;String message = ex.getFailureType().toString();ClientException clientException = findClientException(ex);if (clientException == null) {clientException = findClientException(ex.getFallbackException());}if (clientException != null) {if (clientException.getErrorType() == ClientException.ErrorType.SERVER_THROTTLED) {statusCode = HttpStatus.SERVICE_UNAVAILABLE.value();}cause = clientException;message = clientException.getErrorType().toString();}info.put("status", String.valueOf(statusCode));throw new ZuulException(cause, "Forwarding error", statusCode, message);}

###findClientException

protected ClientException findClientException(Throwable t) {if (t == null) {return null;}if (t instanceof ClientException) {return (ClientException) t;}return findClientException(t.getCause());}

com.netflix.client.ClientException

public class ClientException extends Exception{/*** */private static final long serialVersionUID = -7697654244064441234L;/*** define your error codes here* */public enum ErrorType{GENERAL, CONFIGURATION, NUMBEROF_RETRIES_EXEEDED, NUMBEROF_RETRIES_NEXTSERVER_EXCEEDED, SOCKET_TIMEOUT_EXCEPTION, READ_TIMEOUT_EXCEPTION,UNKNOWN_HOST_EXCEPTION,CONNECT_EXCEPTION,CLIENT_THROTTLED,SERVER_THROTTLED,NO_ROUTE_TO_HOST_EXCEPTION,CACHE_MISSING;static String getName(int errorCode){if (ErrorType.values().length >= errorCode){return ErrorType.values()[errorCode].name();}else{return "UNKNOWN ERROR CODE";}}}
//...
}

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