Jackson反序列化抛异常：com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field的解决方法

需求背景
问题分析
问题解决
- 使用注解@JsonIgnoreProperties
- ObjectMapper对象配置FAIL_ON_UNKNOWN_PROPERTIES

需求背景

第三方服务返回的响应报文是JSON，但是，我们只对其中的一部分感兴趣，故反序列化时创建实体无需包含JSON中的全部字段。

如反序列化"{"name":"JSON","age":"23","address":"北京市西城区","day":1633688895637}"的时候，实体类中唯独没有age字段时，系统抛出的异常如下：

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":"北京市西城区","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)

问题分析

Jackson反序列化JSON字符串的时候，出现这种问题是由于JSON里面包含了实体没有的字段导致反序列化失败。

问题解决

使用注解@JsonIgnoreProperties

在需要转化的对象的类中添加注解@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;
    //年龄
//    private String age;
    //住址
    private String address;
    private Date day;
}

ObjectMapper对象配置FAIL_ON_UNKNOWN_PROPERTIES

String str="{\"name\":\"JSON\",\"age\":\"29\",\"address\":\"北京市朝阳区\",\"addressTest\":\"无对应属性，不转换\"}";;
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
StudentTest value = mapper.readValue(str, StudentTest.class);
System.out.println(value);