JSON parse error: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token

描述：

• 在前后端传递参数时，如果为JSON，后端使用@RequestBody对象类型接受数据，会出现 500/503错误。
• 编译器同时报警告

  2020-07-02 16:57:19.774  WARN 16080 --- [io-7006-exec-10] .w.s.m.s.DefaultHandlerExceptionResolver :
  Resolved [org.springframework.http.converter.HttpMessageNotReadableException: 
  JSON parse error: Cannot deserialize instance of `java.util.ArrayList<com.xxx.xxx.model.order.OrderDetail>` out of START_OBJECT token; 
  nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: 
  Cannot deserialize instance of `java.util.ArrayList<com.xxx.xxx.model.order.OrderDetail>` out of START_OBJECT token
   at [Source: (PushbackInputStream); line: 1, column: 171] (through reference chain: com.xxx.xxx.model.order.OrderInfo["orderDetailList"])]
  

• 警告内容：

  [org.springframework.http.converter.HttpMessageNotReadableException: 
  JSON parse error: Cannot deserialize instance of `java.util.ArrayList<com.xxx.xxx.model.order.OrderInfo>` 
  out of START_OBJECT token
  

  com.fasterxml.jackson.databind.exc.MismatchedInputException:
   Cannot deserialize instance of `java.util.ArrayList<com.xxx.xxx.model.order.OrderInfo>` out of START_OBJECT token
   at [Source: (PushbackInputStream)
  

• 也就是说，在前后端发送数据时，出现JSON格式转换错误，从而访问不到后台接口。
• 不添加 @RequestBody 虽然可以成功访问，但是无法获取到对象数据

解决

• 不要使用对象类型接受，统一使用 Map 接收数据，就不会出现上述情况
• @RequestBody Map<String, Object> data

  @PostMapping("/xxxx/xxxxx")
  public Result submitOrder(@RequestParam("xxxx") String tradeNo, @RequestBody Map<String, Object> data) {
       return Result.ok();
  }