Spring Cloud Gateway中的全局异常处理不能直接用@ControllerAdvice来处理，通过跟踪异常信息的抛出，找到对应的源码，自定义一些处理逻辑来符合业务的需求。

网关都是给接口做代理转发的，后端对应的都是REST API，返回数据格式都是JSON。如果不做处理，当发生异常时，Gateway默认给出的错误信息是页面，不方便前端进行异常处理。

需要对异常信息进行处理，返回JSON格式的数据给客户端。下面先看实现的代码，后面再跟大家讲下需要注意的地方。

自定义异常处理逻辑：

package com.cxytiandi.gateway.exception;import java.util.HashMap;import java.util.Map;import org.springframework.boot.autoconfigure.web.ErrorProperties;import org.springframework.boot.autoconfigure.web.ResourceProperties;import org.springframework.boot.autoconfigure.web.reactive.error.DefaultErrorWebExceptionHandler;import org.springframework.boot.web.reactive.error.ErrorAttributes;import org.springframework.context.ApplicationContext;import org.springframework.http.HttpStatus;import org.springframework.web.reactive.function.server.RequestPredicates;import org.springframework.web.reactive.function.server.RouterFunction;import org.springframework.web.reactive.function.server.RouterFunctions;import org.springframework.web.reactive.function.server.ServerRequest;import org.springframework.web.reactive.function.server.ServerResponse;/** * 自定义异常处理 *  * 
异常时用JSON代替HTML异常信息
 *  * @author yinjihuan * */public class JsonExceptionHandler extends DefaultErrorWebExceptionHandler {    public JsonExceptionHandler(ErrorAttributes errorAttributes, ResourceProperties resourceProperties,            ErrorProperties errorProperties, ApplicationContext applicationContext) {        super(errorAttributes, resourceProperties, errorProperties, applicationContext);    }    /**     * 获取异常属性     */    @Override    protected Map
     
       getErrorAttributes(ServerRequest request, boolean includeStackTrace) {        int code = 500;        Throwable error = super.getError(request);        if (error instanceof org.springframework.cloud.gateway.support.NotFoundException) {            code = 404;        }        return response(code, this.buildMessage(request, error));    }    /**     * 指定响应处理方法为JSON处理的方法     * @param errorAttributes     */    @Override    protected RouterFunction
      
        getRoutingFunction(ErrorAttributes errorAttributes) {        return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse);    }    /**     * 根据code获取对应的HttpStatus     * @param errorAttributes     */    @Override    protected HttpStatus getHttpStatus(Map
       
         errorAttributes) {        int statusCode = (int) errorAttributes.get("code");        return HttpStatus.valueOf(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
        
          response(int status, String errorMessage) {        Map
         
           map = new HashMap<>(); map.put("code", status); map.put("message", errorMessage); map.put("data", null); return map; }}
         
        
       
      
     

覆盖默认的配置：

package com.cxytiandi.gateway.exception;import java.util.Collections;import java.util.List;import org.springframework.beans.factory.ObjectProvider;import org.springframework.boot.autoconfigure.web.ResourceProperties;import org.springframework.boot.autoconfigure.web.ServerProperties;import org.springframework.boot.context.properties.EnableConfigurationProperties;import org.springframework.boot.web.reactive.error.ErrorAttributes;import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;import org.springframework.context.ApplicationContext;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.core.Ordered;import org.springframework.core.annotation.Order;import org.springframework.http.codec.ServerCodecConfigurer;import org.springframework.web.reactive.result.view.ViewResolver;/** * 覆盖默认的异常处理 *  * @author yinjihuan * */@Configuration@EnableConfigurationProperties({ServerProperties.class, ResourceProperties.class})public class ErrorHandlerConfiguration {    private final ServerProperties serverProperties;    private final ApplicationContext applicationContext;    private final ResourceProperties resourceProperties;    private final List
    
      viewResolvers;    private final ServerCodecConfigurer serverCodecConfigurer;    public ErrorHandlerConfiguration(ServerProperties serverProperties,                                     ResourceProperties resourceProperties,                                     ObjectProvider
     
      
       > 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;    }    }
      
     
    

注意点

• 异常时如何返回JSON而不是HTML?

在org.springframework.boot.autoconfigure.web.reactive.error.DefaultErrorWebExceptionHandler中的getRoutingFunction()方法就是控制返回格式的，原代码如下：

@Overrideprotected RouterFunction
    
      getRoutingFunction(            ErrorAttributes errorAttributes) {       return RouterFunctions.route(acceptsTextHtml(), this::renderErrorView)                .andRoute(RequestPredicates.all(), this::renderErrorResponse);}
    

这边优先是用HTML来显示的，想用JSON的改下就可以了，如下：

protected RouterFunction
    
      getRoutingFunction(ErrorAttributes errorAttributes) {       return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse);}
    

• getHttpStatus需要重写

原始的方法是通过status来获取对应的HttpStatus的，代码如下：

protected HttpStatus getHttpStatus(Map
    
      errorAttributes) {      int statusCode = (int) errorAttributes.get("status");      return HttpStatus.valueOf(statusCode);}
    

如果我们定义的格式中没有status字段的话，这么就会报错，找不到对应的响应码，要么返回数据格式中增加status子段，要么重写，我这边返回的是code，所以要重写，代码如下：

@Overrideprotected HttpStatus getHttpStatus(Map
    
      errorAttributes) {    int statusCode = (int) errorAttributes.get("code");    return HttpStatus.valueOf(statusCode);}
    

欢迎加入我的知识星球，一起交流技术，免费学习猿天地的课程（）