com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of

一 问题：

Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `com.XX.Info` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (String)"{"time":"2020-03-19 18:41:01","aa":60000}"; line: 1, column: 2]
	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1592)
	at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1058)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1297)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:326)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4218)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3214)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3182)

就是从json字符串，反序列化为bean.

看了下报错：就是没有默认无参构造器。

public class Info implements Serializable {
    /** 时间 **/
    private Date time;
    /** 持续时间 **/
    private long aa;
 
 
 
    public Info(Date time, long aa) {
        this.time = time;
        this.aa = aa;
    }
    //get\set
...
」

解决办法：

1. 增加默认的无参构造器。

2。 不适用jsackson,改为fastjosn。注意低版本的也会提示：

com.alibaba.fastjson.JSONException: default constructor not found.

升级到1.2.61 版本就好。