spring post jackson的反序列化需要无参构造函数

引言

在测试spring boot 的post传递实体类的过程中发现了一个反向序列化的异常。

异常

JSON parse error: Cannot construct instance of `com.**` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `com.**` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)

 at [Source: (PushbackInputStream); line: 2, column: 2]]

解决方案

在实体类中添加无参构造函数。

原因

jackson的反序列化需要无参构造函数，而我在实体类中添加了有参数的构造函数。

在实体类中添加无参构造函数即可。

修改前

import com.baomidou.mybatisplus.annotation.TableField;

import com.baomidou.mybatisplus.annotation.TableId;

import com.baomidou.mybatisplus.annotation.TableName;

import lombok.Data;

import java.io.Serializable;

@Data

@TableName("user")

public class User implements Serializable {

    @TableId("id")

    private String id;

    @TableField("user_id")

    private String userId;

    @TableField("device_id")

    private String deviceId;

    public User(String deviceId) {

        this.deviceId= deviceId;

    }

}

修改后

import com.baomidou.mybatisplus.annotation.TableField;

import com.baomidou.mybatisplus.annotation.TableId;

import com.baomidou.mybatisplus.annotation.TableName;

import lombok.Data;

import java.io.Serializable;

@Data

@TableName("user")

public class User implements Serializable {

    @TableId("id")

    private String id;

    @TableField("user_id")

    private String userId;

    @TableField("device_id")

    private String deviceId;

    public User() {

        super();

    }

    public User(String deviceId) {

        this.deviceId= deviceId;

    }

}