SpringCloud极简入门｜Spring Cloud Gateway 的全局异常处理（8）

傷城~ 2022-03-18 17:36 237阅读 0赞

### ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p6aHVhbl8x_size_16_color_FFFFFF_t_70][] ###

### 篇章要点 ###

本文将介绍Spring Cloud Gateway如何处理全局异常，统一处理经过路由的异常（返回前端json格式）

### 场景描述  ###

新建 路由Gateway模块：8100和 生产者模块8012（有个test方法）

正常流程访问[http://localhost:8100/api8/test][http_localhost_8100_api8_test] ，此时路由转发返回正常数据

但是，但是，如果此时生产者宕机了（假如哈） ，路由 不配置异常处理的化，展现给调用方的是如下页面

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p6aHVhbl8x_size_16_color_FFFFFF_t_70 1][]

配置处理全局异常后 ，此时返回给调用方的是如下页面

![20190221155609462.png][]

结论：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。可见后者友好一些

### 如何快速配置全局异常 ###

Spring Cloud Gateway中的全局异常处理不能直接用@ControllerAdvice来处理，需自定义一些处理逻辑来符合业务的需求。

很简单就2步：

1.创建JsonExceptionHandler类

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.*;
    
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * @Description: ${todo}(用一句话描述该文件做什么)
     * @Author: zzh
     * @Modified By:
     * @Date: 2019/2/21 15:16
     */
    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<String, Object> 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<ServerResponse> 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<String, Object> 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<String, Object> response(int status, String errorMessage) {
            Map<String, Object> map = new HashMap<>();
            map.put("code", status);
            map.put("message", errorMessage);
            map.put("data", null);
            return map;
        }
    }

2.创建配置信息ErrorHandlerConfiguration

import com.gla.datacenter.filter.JsonExceptionHandler;
    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;
    
    import java.util.Collections;
    import java.util.List;
    
    /**
     * 如：停止privider服务后，此时就会出现json提示的异常
     * {"code":500,"data":null,"message":"Failed to handle request [GET http://localhost:8100/api8/test]: Connection refused: no further information: /192.168.26.70:8012"}
     * @Description: 覆盖默认的异常处理
     * @Author: zzh
     * @Modified By:
     * @Date: 2019/2/21 15:18
     */
    
    @Configuration
    @EnableConfigurationProperties({ServerProperties.class, ResourceProperties.class})
    public class ErrorHandlerConfiguration {
    
    
        private final ServerProperties serverProperties;
    
        private final ApplicationContext applicationContext;
    
        private final ResourceProperties resourceProperties;
    
        private final List<ViewResolver> viewResolvers;
    
        private final ServerCodecConfigurer serverCodecConfigurer;
    
        public ErrorHandlerConfiguration(ServerProperties serverProperties,
                                         ResourceProperties resourceProperties,
                                         ObjectProvider<List<ViewResolver>> 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;
        }
    }

### 总结 ###

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：

@Override
    protected RouterFunction<ServerResponse> 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<ServerResponse> 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<String, Object> 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：

@Override
    protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
        int statusCode = (int) errorAttributes.get("code");
        return HttpStatus.valueOf(statusCode);
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p6aHVhbl8x_size_16_color_FFFFFF_t_70]: /images/20220318/239cf840ef644c39aa86e267d4699d54.png
[http_localhost_8100_api8_test]: http://localhost:8100/api8/test
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p6aHVhbl8x_size_16_color_FFFFFF_t_70 1]: /images/20220318/9d1c6bd7000247f3b522944d823f7cb0.png
[20190221155609462.png]: /images/20220318/2edb1037406840c2a0d4270365ef2798.png