👀 Views: 61 💬 Answers: 1 📅 Created: 2025-06-08

java jackson deserialization Java

I'm dealing with I've looked through the documentation and I'm still confused about I'm working with an scenario with deserializing a `Map<CustomKey, Value>` where `CustomKey` is a complex object. The map is stored in JSON format, but when I try to deserialize it using Jackson's `ObjectMapper`, I get a `com.fasterxml.jackson.databind.JsonMappingException`. The behavior indicates that Jackson need to find a suitable constructor or factory method for `CustomKey`. Here's the relevant part of my code: ```java import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JsonDeserializer; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.annotation.JsonDeserialize; import java.io.IOException; import java.util.Map; public class MyClass { private Map<CustomKey, Value> myMap; @JsonDeserialize(using = MyMapDeserializer.class) public Map<CustomKey, Value> getMyMap() { return myMap; } } class CustomKey { private String keyPart1; private String keyPart2; public CustomKey(String keyPart1, String keyPart2) { this.keyPart1 = keyPart1; this.keyPart2 = keyPart2; } // equals and hashCode methods } class MyMapDeserializer extends JsonDeserializer<Map<CustomKey, Value>> { @Override public Map<CustomKey, Value> deserialize(JsonParser p, DeserializationContext ctxt) throws IOException { // Custom deserialization logic } } ``` I have tried adding a no-argument constructor to `CustomKey`, but that didn't help. Additionally, I've confirmed that the JSON structure matches the expected format, e.g., ```json {"keyPart1_keyPart2": {"valueField": "exampleValue"}} ``` However, I'm still running into issues. I would appreciate any insights into how I can resolve this deserialization question or if there's a better approach I can take with Jackson to handle complex keys. Is there a specific way to configure the `ObjectMapper` or the deserializer to ensure that my `CustomKey` can be correctly instantiated from the JSON? Thank you! This is part of a larger CLI tool I'm building. Is this even possible? I recently upgraded to Java LTS. Any examples would be super helpful.