Spring Cloud Gateway Hystrix fallback获取异常信息的处理

Gateway Hystrix fallback获取异常信息

gateway fallback后，需要知道请求的是哪个接口以及具体的异常信息，根据不同的请求以及异常进行不同的处理。一开始根据网上一篇博客上的做法：

pom.xml：

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>

application.yml：

spring:
  cloud:
    gateway:
      discovery:
        locator:
          enabled: false
          lowerCaseServiceId: true
      routes:
        - id: auth-server
          uri: lb://MS-OAUTH2-SERVER
          predicates:
            - Path=/**
      default-filters:
        - name: Hystrix
          args:
            name: fallbackcmd
            fallbackUri: forward:/fallback

然后fallback就是这样：

@RestController
@Slf4j
public class FallbackController {

    @RequestMapping(value = "/fallback")
    @ResponseStatus
    public Mono<Map<String, Object>> fallback(ServerWebExchange exchange, Throwable throwable) {
        Map<String, Object> result = new HashMap<>(3);
        ServerHttpRequest request = exchange.getRequest();
        log.error("接口调用失败，URL={}", request.getPath().pathWithinApplication().value(), throwable);
        result.put("code", 60002);
        result.put("data", null);
        result.put("msg", "接口调用失败!");
        return Mono.just(result);
    }
}

但是测试发现，这样取出来的接口地址只是“/fallback”本身，并且没有异常信息：

在这里插入图片描述

后来我重新到HystrixGatewayFilterFactory类中去查看，发现了异常信息其实在exchange里：

在这里插入图片描述

而请求的接口也通过debug找到了：

所以将代码改成如下：

@RestController
@Slf4j
public class FallbackController {

    @RequestMapping(value = "/fallback")
    @ResponseStatus
    public Mono<Map<String, Object>> fallback(ServerWebExchange exchange) {
        Map<String, Object> result = new HashMap<>(3);
        result.put("code", 60002);
        result.put("data", null);
        Exception exception = exchange.getAttribute(ServerWebExchangeUtils.HYSTRIX_EXECUTION_EXCEPTION_ATTR);
        ServerWebExchange delegate = ((ServerWebExchangeDecorator) exchange).getDelegate();
        log.error("接口调用失败，URL={}", delegate.getRequest().getURI(), exception);
        if (exception instanceof HystrixTimeoutException) {
            result.put("msg", "接口调用超时");
        } else if (exception != null && exception.getMessage() != null) {
            result.put("msg", "接口调用失败: " + exception.getMessage());
        } else {
            result.put("msg", "接口调用失败");
        }
        return Mono.just(result);
    }
}

正常取到请求路径以及异常信息：

关于 hystrix 的异常 fallback method wasn't found

消费者服务--service 的实现如下：

@Service
public class BookService {
    @Autowired
    public RestTemplate  restTemplate;
    @HystrixCommand(fallbackMethod = "addServiceFallback")
    public  Book   getBook( Integer  bookId ){
        return  restTemplate.getForObject("http://provider-service/boot/book?bookId={bookId}",Book.class , bookId);
    }
    public  String  addServiceFallback(){
        System.out.println("error addServiceFallback.... ");
        return  "error" ;
    }
}

就会出现如下所述的异常

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Fri May 25 14:27:51 CST 2018
There was an unexpected error (type=Internal Server Error, status=500).
fallback method wasn't found: addServiceFallback([class java.lang.Integer])

这是因为指定的备用方法 addServiceFallback 和原方法getBook 的参数个数，参数类型不同造成的；

修改addServiceFallback 方法：

public  String addServiceFallback(Integer  bookId){
    System.out.println("error addServiceFallback.... ");
    return  "error" ;
}

继续运行，就会出现如下所述的异常

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Fri May 25 14:32:24 CST 2018
There was an unexpected error (type=Internal Server Error, status=500).
Incompatible return types. Command method: public com.bmcc.springboot.model.Book com.bmcc.springboot.service.BookService.getBook(java.lang.Integer); Fallback method: public java.lang.String com.bmcc.springboot.service.BookService.addServiceFallback(java.lang.Integer); Hint: Fallback method 'public java.lang.String com.bmcc.springboot.service.BookService.addServiceFallback(java.lang.Integer)' must return: class com.bmcc.springboot.model.Book or its subclass

这是因为指定的备用方法 addServiceFallback 和原方法getBook 虽然参数个数，参数类型相同，但是方法的返回值类型不同造成的；

修改addServiceFallback 方法：

public  Book  addServiceFallback(Integer  bookId){
    System.out.println("error addServiceFallback.... ");
    return  new Book() ;
}

继续运行，这样就可以看到当一个服务提供者异常关闭时，消费者（消费者采用轮询的方式消费服务）再继续访问服务时，不会抛出异常页面，而是如下：

{"bookId":0,"bookName":null,"price":null,"publisher":null}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持自学编程网。

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