Problem to deserialize json to java object of generic type with jackson 2.13.4.2 - jackson

Question

There's a message defined as below, note there're different implementations of the generic type M
// The message definition
#Value
#Builder(toBuilder = true)
#Jacksonized
public class MyMessage<M> {
#Builder.Default
Map<String, String> props = new HashMap<>();
M content;
}
// One implementation of the generic type M in MyMessage
class ContentType1 {
String name;
SomeSimplePojo pojo;
Map<String, String> contentProps;
}
Here's an example of above message:
{
"props": {
"trace-id": "3468f6022b749dbc"
},
"content": {
"name": "contentExample1",
"pojo": {
"field1": "val1",
"field2": "val2"
},
"contentProps": {
"/Count": "9",
"/Email": "someone#stackoverflow.com"
}
}
}
The message was deserialized basically with below code snippet, by com.fasterxml.jackson.* version 2.10.4. It worked fine before.
ObjectMapper objectMapper = new ObjectMapper();
MyMessage<String> rawMsg = objectMapper.readValue(jsonStr, new TypeReference<MyMessage<String>>() {});
// Here clazzOfM is the class of type M
MyMessage<M> convertedMsg = MyMessage.<M>builder().content(objectMapper.convertValue(rawMsg.getContent(), clazzOfM)).props(rawMsg.getProps()).build();
But recently, I upgraded com.fasterxml.jackson.databind to 2.13.4.2, all other com.fasterxml.jackson.* to 2.13.4. Then it failed at this line MyMessage<String> rawMsg = objectMapper.readValue(jsonStr, new TypeReference<MyMessage<String>>() {}); with Exception, which points to the generic type M, field content at column 52:
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize value of type `java.lang.String` from Object value (token `JsonToken.START_OBJECT`)
at [Source: (String)"{"props":{"trace-id":"3468f6022b749dbc"},"content":{"name":"contentExample1","pojo":{"field1":"val1","field2":"val2"},"contentProps":{"/Count":"9","/Email":"someone#stackoverflow.com"}}}"; line: 1, column: 52] (through reference chain: com.demo.example.MyMessage$MyMessageBuilder["content"])
at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1741)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1515)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1420)
at com.fasterxml.jackson.databind.DeserializationContext.extractScalarFromObject(DeserializationContext.java:932)
at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:62)
at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:11)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeSetAndReturn(MethodProperty.java:158)
at com.fasterxml.jackson.databind.deser.BuilderBasedDeserializer.vanillaDeserialize(BuilderBasedDeserializer.java:293)
at com.fasterxml.jackson.databind.deser.BuilderBasedDeserializer.deserialize(BuilderBasedDeserializer.java:217)
at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:323)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4674)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3629)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3612)
I tried to change the problematic line to MyMessage<M> rawMsg = objectMapper.readValue(jsonStr, new TypeReference<MyMessage<M>>() {});, no exception then, but I still have two questions.
Is the above change a correct approach to deserialize json text to MyMessage by jackson 2.13.4(.2)? What is the best practice to this kind of deserialization if the above isn't.
After the above change, I notice that the type of rawMsg.content is LinkedHashMap, it isn't M(CotentType1 in this test) as I expected. But the type of convertedMsg.content IS ContentType1 after executing this converting line MyMessage<M> convertedMsg = MyMessage.<M>builder().content(objectMapper.convertValue(rawMsg.getContent(), clazzOfM)).props(rawMsg.getProps()).build();.
I can't understand why the type of rawMsg.content is LinkedHashMap instead of ContentType1. Could someone help explain?