Jackson反序列化拋異常：com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field的解決方法

目錄

• 需求背景
• 問題分析
• 問題解決
  • 使用注解@JsonIgnoreProperties
  • ObjectMapper對象配置FAIL_ON_UNKNOWN_PROPERTIES

需求背景

  第三方服務返回的響應報文是JSON，但是，我們只對其中的一部分感興趣，故反序列化時創建實體無需包含JSON中的全部字段。

  如反序列化"{"name":"JSON","age":"23","address":"北京市西城區","day":1633688895637}"的時候，實體類中唯獨沒有age字段時，系統拋出的異常如下：

Parse object to Object error
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "age" (class dto.StudentTest), not marked as ignorable (3 known properties: "name", "address", "day"])
 at [Source: (String)"{"name":"JSON","age":"23","address":"北京市西城區","day":1633688895637}"; line: 1, column: 23] (through reference chain: com.cloud.isavana.media.module.report.dto.StudentTest["age"])
	at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:61)
	at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:987)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:1974)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1701)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1679)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:330)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:187)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3548)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3516)

問題分析

  Jackson反序列化JSON字符串的時候，出現這種問題是由於JSON里面包含了實體沒有的字段導致反序列化失敗。

問題解決

使用注解@JsonIgnoreProperties

  在需要轉化的對象的類中添加注解@JsonIgnoreProperties(ignoreUnknown = true)，示例如下：

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import java.io.Serializable;
import java.util.Date;

/**
 * @Author: Wiener
 * @Date: 2021/10/8 17:02
 */
@Getter
@Setter
@ToString
@JsonIgnoreProperties(ignoreUnknown = true)
public class StudentTest implements Serializable {

    private static final long serialVersionUID = -5246589941647210011L;
    //姓名
    private String name;
    //年齡
//    private String age;
    //住址
    private String address;
    private Date day;
}

ObjectMapper對象配置FAIL_ON_UNKNOWN_PROPERTIES

String str="{\"name\":\"JSON\",\"age\":\"29\",\"address\":\"北京市朝陽區\",\"addressTest\":\"無對應屬性，不轉換\"}";;
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
StudentTest value = mapper.readValue(str, StudentTest.class);
System.out.println(value);

Reference

• https://www.cnblogs.com/EasonJim/p/7990909.html

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