[英]Nested Json to Map using Jackson
I'm trying to dynamically parse some JSON to a Map. 我正在尝试动态地将一些JSON解析为Map。 The following works well with simple JSON 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. 但是当我尝试将一些更复杂的JSON与嵌套信息一起使用时失败了。 I'm trying to parse the sample data from json.org 我正在尝试解析json.org中的示例数据
{
"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.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token 线程“main”中的异常com.fasterxml.jackson.databind.JsonMappingException:无法从START_OBJECT标记中反序列化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?
I think the error occurs because the minute Jackson encounters the { character, it treats the remaining content as a new object, not a string. 我认为错误的发生是因为杰克逊遇到{字符时,它将剩余内容视为新对象,而不是字符串。 Try Object as map value instead of String. 尝试将Object作为映射值而不是String。
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 产量
{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}}}}}
Wrap your Map into a dumb object as container, like this: 将Map作为容器包装到一个哑对象中,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Object映射器,使用Joda模块的示例Object mapper:
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 ;-) 希望有所帮助;-)
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