java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to xxx解决

相关代码：

  com.fasterxml.jackson.core
  jackson-databind
  2.12.2

public static void main(String[] args) throws JsonProcessingException {
Test test1 = new ObjectMapper().readValue("{"content":"1","map":{"test":{},"test1":{}}}", Test.class);
Map map = test1.getMap();
Test test = (Test) map.get("test");
}

运行报错：

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to xxx

调试源码：

@Override
public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
{
switch (p.currentTokenId()) {
case JsonTokenId.ID_START_OBJECT:
{
JsonToken t = p.nextToken();
if (t == JsonToken.END_OBJECT) {
return new LinkedHashMap(2);
}
}
...

Map中对象返回为LinkedHashMap，故转换报错

调试源码小技巧：若不知道接口方法的实现类，可在接口的方法上打断点

将LinkedHashMap转成字符串，在解析成对象解决

JSON.parseObject(JSON.toJSONString(map.get("message")), Test.class);

public static void main(String[] args) throws JsonProcessingException {
Test test1 = new ObjectMapper().readValue("{"content":"1","map":{"test":{},"test1":{}}}", Test.class);
Map map = test1.getMap();
Test test = JSON.parseObject(JSON.toJSONString(map.get("message")), Test.class);
}

JSON包依赖

  com.alibaba
  fastjson
  1.2.80

常用JSON解析依赖

GSONjacksonfastjson

JSON官网：
https://www.json.org/json-en.html

桃之夭夭，灼灼其华