##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：

@Override	public 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
    
      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
    
      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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