Json String来映射转换器， [英] Json String to map convertor,

问题描述

我正在尝试编写嵌套JsonObject的通用代码来映射转换。

I am trying to write a generic code for nested JsonObject to map conversion.

我有一个示例JSONObject为

I have a sample JSONObject as

{
  "glossary": {
    "title": "example glossary",
    "GlossDiv": {
      "title": "S",
      "GlossList": {
        "GlossEntry": {
          "ID": "SGML",
          "SortAs": "SGML",
          "GlossTerm": "Standard Generalized \n Markup Language",
          "GlossDef": {
            "para": "A  DocBook.",
            "GlossSeeAlso": [
              "GML",
              "XML"
            ]
          },
          "GlossSee": "markup"
        }
      }
    }
  }
}

我想将其转换为具有键值的地图as

I want to convert it into map having key value as

glossary.title = "example glossary",
glossary.GlossDiv.title = "S",
glossary.GlossDiv.GlossList.GlossEntry.ID ="SGML",
glossary.GlossDiv.GlossList.GlossEntry.SortAs ="SGML",
glossary.GlossDiv.GlossList.GlossEntry.GlossTerm="Standard Generalized 
Markup Language",
glosary.GlossDiv.GlossList.GlossEntry.GlossDef.para ="A  DocBook.",
glossary.GlossDiv.GlossList.GlossEntry.GlossDef.GlossSeeAlso_0 = "GML",
glossary.GlossDiv.GlossList.GlossEntry.GlossDef.GlossSeeAlso_1 = "XML",
glossary.GlossDiv.GlossList.GlossEntry.GlossDef.GlossSee = "markup"

推荐答案

这是使用 Jackson ：

public final class JsonUtils {
    public static <T> Map<String, T> readMap(String json) throws Exception {
        if (json == null)
            return null;

        ObjectReader reader = new ObjectMapper().readerFor(Map.class);
        MappingIterator<Map<String, T>> it = reader.readValues(json);

        if (it.hasNextValue()) {
            Map<String, T> res = it.next();
            return res.isEmpty() ? Collections.emptyMap() : res;
        }

        return Collections.emptyMap();
    }
}

这是如何阅读使用给定的utilit方法从json映射：

Map<String, String> map = flatMap(new LinkedHashMap<>(), "", JsonUtils.readMap(json));

最后，这是如何转换地图进入必需的地图（可能这可以在杰克逊引擎内完成，提供自定义反序列化器，但我不确切知道如何，这就是为什么它对我来说更容易手动实现它：

And finally, this is how to transfrom Map into required Map (probably this could be done within Jackson engine, with provided custom deserializers or so, but I do not know exactly how, and thats why it is easier to me to implement it manually):

public static Map<String, String> flatMap(Map<String, String> res, String prefix, Map<String, Object> map) {
    for (Map.Entry<String, Object> entry : map.entrySet()) {
        String key = prefix + entry.getKey();
        Object value = entry.getValue();

        if (value instanceof Map)
            flatMap(res, key + '.', (Map<String, Object>)value);
        else
            res.put(key, String.valueOf(value));
    }

    return res;
}

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