当JsonProperty有时是数组，有时是单个对象时，Jackson会对其进行解析 [英] Jackson desrialize when JsonProperty is sometimes array and sometimes a single Object

问题描述

我在发布之前搜索过Stack Overflow，但是Jackson没有解决方案。


这是服务器响应：

I've searched Stack Overflow before posting, but there were no solutions for Jackson.

Here is a server response:

{
  "ok": true,
  "result": [
    {
      "update_id": 489881731,
      //rest 
    },
    {
      "update_id": 489881732,
      //rest
    }
  ]
}

如您所见，物业结果是一个数组。


现在这是另一个回复：

As you see property "result" is an array.

Now this is another response:

{
  "ok": true,
  "result": {
    "id": 211948704,
    "first_name": "ربات ادمین‌های تلگرام",
    "username": "tgAdminsBot"
  }
}

此处result是一个单独的对象。


这是我的类，我想将内容反序列化。我为 TObject 写了一个自定义反序列化器当然：

Here "result" is a single object.

This is my class I want to deserialize content to it. I wrote a custom deserializer for TObject of course:

public class Result
{
    private TObject[] result;
    private boolean ok;

    public void setOk (boolean ok) {//code}

    public void setResult (TObject[] result) {//code}


    public TObject[] getResult () {//code}

    public boolean getOk (){//code}
}

所以我在课堂上假设 result是一个 TObject的秒。现在我该怎么办？ 对两个字段使用 @JsonProperty（result），其中一个字段是 TObject s和一个是单个 TObject 好吗？


如果不是我还能做什么？

So I assumed in my class that "result" is an array of TObjects. Now what can I do? Is using @JsonProperty("result") for two fields which one is an array of TObjects and one is a single TObject OK?

If not what else can I do?

推荐答案

如果启用 DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY 两者

{result：[]} 和

{result： {}} 可以解析为

class Result{
   List result;
}

文档链接

确定是否可以强制使用非数组
（使用JSON）值来使用Java集合（数组，
java.util.Collection）类型的功能。如果启用，收集反序列化器将
尝试处理非数组值，就像它们围绕
JSON数组隐式一样。此功能旨在用于
兼容性/互操作性原因，用于处理包（如
XML-to-JSON转换器）在没有
的情况下遗漏JSON数组的包数组中的单个元素。默认情况下禁用功能。

Feature that determines whether it is acceptable to coerce non-array (in JSON) values to work with Java collection (arrays, java.util.Collection) types. If enabled, collection deserializers will try to handle non-array values as if they had "implicit" surrounding JSON array. This feature is meant to be used for compatibility/interoperability reasons, to work with packages (such as XML-to-JSON converters) that leave out JSON array in cases where there is just a single element in array. Feature is disabled by default.

演示如何将其用于OP输入jsons和POJO：

Demo how to use it for OP input jsons and POJOs:

ObjectMapper mapper = new ObjectMapper()
mapper.enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
Result result = mapper.readValue(Result.class;

可与<$一起使用c $ c> @JsonFormat 如果由于某种原因你不喜欢mapper版本

Can be used with @JsonFormat above class or field if you don't like mapper version for some reason

@JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY)

PS。其他有关此问题的SO问题： LINK

PS. Other SO questions about this problem: LINK

这篇关于当JsonProperty有时是数组，有时是单个对象时，Jackson会对其进行解析的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！