如何在 JAVA 中忽略 NullNode for deserialization JSON

Question

所以问题是下一个：我有POJO，比如：@Data@Accessors(chain = true)@JsonInclude(Include.NON_NULL)public class TestPOJO {  private Long id;  private String name;  private JsonNode jsonNode;我也有json喜欢{   "id":1   "name": "foo"   "jsonNode":null}当我尝试反序列化最后一个ObjectMapper objectMapper = new ObjectMapper();TestPOJO testPojo = objectMapper.readValue(<json String>, TestPOJO.class);我在字段所在的位置获取对象，但我需要在如何修复它？testPojojsonNodeNullNodetestPojo == null

Answer 1

添加一个扩展的类，如果为 null，则返回 null：JsonDeserializer<JsonNode>parser.getText()

import com.fasterxml.jackson.core.JsonParser;

import com.fasterxml.jackson.databind.DeserializationContext;

import com.fasterxml.jackson.databind.JsonDeserializer;

import com.fasterxml.jackson.databind.JsonNode;

import java.io.IOException;

public class JsonNodeDeserializer extends JsonDeserializer<JsonNode> {

    @Override

    public JsonNode deserialize(JsonParser parser, DeserializationContext context)

            throws IOException {

        String value = parser.getText();

        if(value == null) {

            return null;

        }

        return (JsonNode) context.findRootValueDeserializer(context.constructType(JsonNode.class)).deserialize(parser, context);

    }

}

然后对属性进行注释，以告诉 Jackson 使用您的自定义反序列化程序：jsonNode@JsonDeserialize(using = JsonNodeDeserializer.class)

@Data

@Accessors(chain = true)

@JsonInclude(Include.NON_NULL)

public class TestPOJO {

  private Long id;

  private String name;

  @JsonDeserialize(using = JsonNodeDeserializer.class)

  private JsonNode jsonNode;

  // getters and setters

}