春云netflix和HystrixObservable-> JsonMappingException [英] Spring cloud netflix and HystrixObservable --> JsonMappingException

问题描述

有关代码，请参见我的微小4类 github项目

For code, see my tiny 4 class github project

我正在使用Spring FeignClients连接到Rest服务. Feign客户端的基本(非异步)形式如下所示:

I am using Spring FeignClients to connect to a rest service. This is what the Feign client looks like in its basic (non-async) form:

@FeignClient(value="localhost:8080/products", decode404 = true)
public interface ProductClient {
    @RequestMapping(value="/{id}")
    Product getById(@PathVariable("id") String id);
}

现在，我想使用Observable异步进行此操作. Spring文档中严重缺乏有关此方面的信息，只有

Now I wanted to do that asynchronously, using an Observable. Information on this is severely lacking in the Spring docs, there is only a small paragraph that tells you to use a HystrixCommand. That's all, no explanation, no sampe code.

在另一篇博客文章中，有人告诉我改用HystrixObservable.所以我尝试了:

In another blog post, I was told to use a HystrixObservable instead. And so I tried that:

@FeignClient(value="localhost:8080/products", decode404 = true)
public interface ProductClient {
    @RequestMapping(value="/{id}")
    HystrixObservable<Product> getById(@PathVariable("id") String id);
}

无论哪种方式，使用HystrixCommand或HystrixObservable，都会抛出错误: com.fasterxml.jackson.databind.JsonMappingException:无法构造com.netflix.hystrix.HystrixObservable的实例

Either way, with a HystrixCommand or HystrixObservable, it throws me the error: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.netflix.hystrix.HystrixObservable

我理解为什么会出现该错误，因为Spring Boot会自动将一个Decoder附加到FeignClient上，以使用Jackson来反序列化响应.从响应值派生反序列化为响应的类型.

I understand why it is giving that error, since Spring Boot automatically attaches a Decoder to the FeignClient to deserialize the response using Jackson. And the type to deserialize the response into is derived from the return value.

我可以尝试配置自定义解码器或手动构建Feign客户端，但这有点违背了Spring Boot的全部目的:它可以自动运行(尽管在这里和那里有一些配置).

I could try to configure a custome Decoder or manually build the Feign clients, but that kind-of defeats the whole purpose of Spring Boot: that it works automagically (albeit with a bit of configuration here and there).

所以我的问题是:这应该如何工作?

And so my question is: how is this supposed to work?

推荐答案

如果有人在升级到spring-cloud:1.3.+后开始出现此错误，请确保已启用hystrix-feign.

If anybody starts getting this error after upgrading to spring-cloud:1.3.+ make sure you have hystrix-feign enabled.

feign.hystrix.enabled=true

已添加此功能，因此假装默认情况下不会将调用包装在hystrix命令中.

This was added so feign does not wrap calls in hystrix commands by default.

https://github.com/spring-cloud/spring -cloud-netflix/issues/1277

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