Java 使用 Jackson 将 Json 嵌套到 Map
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Nested Json to Map using Hymanson
提问by user2229544
I'm trying to dynamically parse some JSON to a Map. The following works well with simple JSON
我正在尝试将一些 JSON 动态解析为 Map。以下适用于简单的 JSON
String easyString = "{\"name\":\"mkyong\", \"age\":\"29\"}";
Map<String,String> map = new HashMap<String,String>();
ObjectMapper mapper = new ObjectMapper();
map = mapper.readValue(easyString,
new TypeReference<HashMap<String,String>>(){});
System.out.println(map);
But fails when I try to use some more complex JSON with nested information. I'm trying to parse the sample data from json.org
但是当我尝试使用一些带有嵌套信息的更复杂的 JSON 时失败了。我正在尝试解析来自 json.org 的示例数据
{
"glossary": {
"title": "example glossary",
"GlossDiv": {
"title": "S",
"GlossList": {
"GlossEntry": {
"ID": "SGML",
"SortAs": "SGML",
"GlossTerm": "Standard Generalized Markup Language",
"Acronym": "SGML",
"Abbrev": "ISO 8879:1986",
"GlossDef": {
"para": "A meta-markup language, used to create markup languages such as DocBook.",
"GlossSeeAlso": [
"GML",
"XML"
]
},
"GlossSee": "markup"
}
}
}
}
}
I get the following error
我收到以下错误
Exception in thread "main" com.fasterxml.Hymanson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token
线程“main”com.fasterxml.Hymanson.databind.JsonMappingException 中的异常：无法从 START_OBJECT 令牌中反序列化 java.lang.String 的实例
Is there a way to parse complex JSON data into a map?
有没有办法将复杂的 JSON 数据解析成地图？
回答by JamesB
I think the error occurs because the minute Hymanson encounters the { character, it treats the remaining content as a new object, not a string. Try Object as map value instead of String.
我认为发生错误是因为 Hymanson 遇到 { 字符的那一刻，它将剩余内容视为新对象，而不是字符串。尝试将对象作为映射值而不是字符串。
public static void main(String[] args) throws IOException {
Map<String,String> map = new HashMap<String,String>();
ObjectMapper mapper = new ObjectMapper();
map = mapper.readValue(x, new TypeReference<HashMap>(){});
System.out.println(map);
}
output
输出
{glossary={title=example glossary, GlossDiv={title=S, GlossList={GlossEntry={ID=SGML, SortAs=SGML, GlossTerm=Standard Generalized Markup Language, Acronym=SGML, Abbrev=ISO 8879:1986, GlossDef={para=A meta-markup language, used to create markup languages such as DocBook., GlossSeeAlso=[GML, XML]}, GlossSee=markup}}}}}
回答by Guido Medina
Wrap your Map into a dumb object as container, like this:
将您的 Map 包装成一个哑对象作为容器，如下所示：
public class Country {
private final Map<String,Map<String,Set<String>>> citiesAndCounties=new HashMap<>;
// Generate getters and setters and see the magic happen.
}
The rest is just working with your Object mapper, example Object mapper using Joda module:
其余的只是使用您的对象映射器，使用 Joda 模块的示例对象映射器：
public static final ObjectMapper JSON_MAPPER=new ObjectMapper().
disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES).
setSerializationInclusion(JsonInclude.Include.NON_NULL).
disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS).
registerModule(new JodaModule());
// Calling your Object mapper
JSON_MAPPER.writeValueAsString(new Country());
Hope that helps ;-)
希望有帮助;-)
