javascript - Map 未映射

Question

前端将此 json 发送到我的 API

{  
  "parameters":{  
      "MAIL_BODY":"saffsa",
      "MAIL_FROM":"sffasafs",
      "MAIL_RECEIVED_DATE":"asfasf",
      "MAIL_SUBJECT":"asfafs",
      "MAIL_TO":"ssfafs"
   },
   "templateID":"9093",
   "deliveryChannel":"NONE"
}

Controller :

 @RequestMapping(value = "/previewDocument", method = RequestMethod.POST, produces = "application/pdf")
public byte[] previewDocument(@RequestBody Map<String, String> parameters, @RequestBody String templateID, @RequestBody String deliveryChannel) {
    // TODO
}

但是我在我的后端日志中得到了这个

2019-02-22 10:34:55.068 WARN 9976 --- [nio-8083-exec-7] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of java.lang.String out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.lang.String out of START_OBJECT token at [Source: (PushbackInputStream); line: 1, column: 15] (through reference chain: java.util.LinkedHashMap["parameters"])]

我不明白这是什么问题。 parameters 似乎是一个 Map 对吧？有人可以解释一下为什么这不起作用吗？

Answer 1

替换Map<String, String>与 Map<String, Object>并且解析将会成功。内部对象被解析为 Map<String, String> .
您将需要在方法主体中强制转换/询问值的类型，例如

if (parameters.get("parameters") instanceof Map) {
  Map<String, String> parametersMap = (Map<String, String>)parameters.get("parameters");
  String body = parametersMap.get("MAIL_BODY");
}