开发环境

问题描述

调用接口报错，前端提示

{
    "code": 400,
    "message": "DemoConsumer#getUserRole(String) failed and no fallback available."
}

后端代码报错为

Caused by: feign.codec.DecodeException: Error while extracting response for type [java.util.List<java.lang.String>] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token
Caused by: org.springframework.web.client.RestClientException: Error while extracting response for type [java.util.List<java.lang.String>] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of 
Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token
 at [Source: (PushbackInputStream); line: 1, column: 1]

问题分析

是调用 getUserRole 接口报的错

先看生产者这个接口的定义

/**
 * 获取用户对应的角色权限
 *
 * @param userId 用户角色权限
 * @return List<String>
 **/
@PostMapping("/getUserRole")
public List<String> getUserRole(@RequestParam(value = "userId") String userId)

我在 web 项目中调用如下

List<String> roleList = consumer.getUserRole(result.getData().getId());

问题解决

看上去没什么问题，打入断点到上面的代码，发现这里 Id 没有值，导致报错

把 Id 设置有值之后，错误消失，问题解决。