- 傑克遜地圖<字符串，對象>實施

Question

的系列化我有以下類：

public class Some implements Map<String, Object>{ 
    private Map<String, Object> innerMap; 
    //implementation that can only set innerMap in constructor and cannot add or remove values 
} 

的問題是，我不能在傑克遜正確反序列化這一點。如果我序列無默認輸入，這是確定的，因爲它被序列化爲{「一」：「二」}，正確地反序列化（我不得不實施解串器

return new Some(jp.readValueAs(new TypeReference<HashMap<String,Object>>(){})); 

當我使用默認的打字開啓，這個序列化爲

["com.class.Some",{"one":"two"}] 

但反序列化拋出

com.fasterxml.jackson.databind.JsonMappingException: Unexpected token (START_OBJECT), expected START_ARRAY: need JSON Array to contain As.WRAPPER_ARRAY type information for class java.util.HashMap 

有什麼想法？

Answer 1

這正是我需要的 - 自定義解串器：

public class SomeDeserializer extends JsonDeserializer<Some> { 

    @Override 
    public Object deserializeWithType(JsonParser jsonParser, DeserializationContext ctxt, TypeDeserializer typeDeserializer) throws IOException { 
     return typeDeserializer.deserializeTypedFromObject(jsonParser, ctxt); 
    } 

    @SuppressWarnings("unchecked") 
    @Override 
    public Some deserialize(JsonParser jp, DeserializationContext ctxt) 
      throws IOException { 
     JsonDeserializer<Object> deserializer = ctxt.findRootValueDeserializer(
       ctxt.getTypeFactory().constructMapType(Map.class, String.class, Object.class)); 

     return new Some((Map) deserializer.deserialize(jp, ctxt, new HashMap<>())); 
    } 
} 

Answer 2

註釋你的構造與@JsonCreator：

public static void main(String[] args) throws IOException { 
    ObjectMapper mapper = new ObjectMapper(); 
    mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL); 

    Some some = new Some(new HashMap<String, Object>() {{put("a", 1);}}); 

    String json = mapper.writeValueAsString(some); 
    System.out.println("serialized : " + json); 

    some = mapper.readValue(json, Some.class); 
    System.out.println("deserialized: " + some); 
} 

// Read only delegating Map 
public static class Some extends AbstractMap<String, Object> { 
    private Map<String, Object> delegate; 

    @JsonCreator 
    public Some(Map<String, Object> delegate) { 
     this.delegate = Collections.unmodifiableMap(delegate); 
    } 

    @Override 
    public Set<Entry<String, Object>> entrySet() { 
     return delegate.entrySet(); 
    } 
}