如何根据json中的属性编写jackson反序列化器

Posted 2021-04-06

我想在类Type上编写json反序列化器，以便当基于名称从给定的json反序列化Type时，它将值（接口类型为Being）映射到基于某些工厂方法的当前实现，该工厂方法根据名称返回正确的类名，并填充剩余的类没有任何明确的反序列化，也没有明确地使用new创建TigerBeing或HumanBeing的对象。

我尝试使用@jsonCreator但是我必须使用new初始化整个HumanBeing或TigerBeing并在构造函数中传递所有json。我需要自动映射进一步用作进一步pojo的类型可能非常复杂。

{type:[{
    "name": "Human",
    "value": { 
        "height":6,
        "weight":100,
        "languages":["spanish","english"]
    }
 },
{
"name":"Tiger",
"value":{
    "extinct":1,
    "found":["Asia", "America", "Europe", "Africa"]
}
}
]}

I have:

public class Type {
    String name;
    Being value;
}

public interface Being {
}

public class TigerBeing implements Being { 
    Integer extinct;
    String[] found;
}

public class HumanBeing implement Being {
    Integer height;
    Integer weight;
    String[] languages;
}

答案

import java.io.IOException;

public class BeingDeserializer extends JsonDeserializer<Being> {

  @Override
  public Expertise deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonMappingException {

    JsonNode node = jp.getCodec().readTree(jp);
    String beingName = node.get("name").asText();
    JsonNode valueNode = node.get("value");
    BeingName beingByName = ExpertiseName.getBeingByName(beingName);
    if(beingByName ==null) {
      throw new JsonMappingException("Invalid Being " + beingName);
    }

    Being being =  JsonUtils.getObjectFromJsonNode(valueNode,
            ExpertiseFactory.getExpertise(beingByName).getClass());
    return being;
  }
}

通过这种方式，我能够解决上述问题。