springboot post 请求异常

╰+哭是因爲堅強的太久メ 2022-01-21 06:37 261阅读 0赞

### 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;
        }
    }