一、引入maven依赖

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.66</version>
        </dependency>

二、字段重命名

1.创建一个测试实体

import lombok.Data;

import java.io.Serializable;

/**
 * @类名 WeChatBusinessLicenseInfo
 * @描述 营业执照/登记证书信息（测试用）
 * @版本 1.0
 * @创建人 XuKang
 * @创建时间 2021/12/24 10:43
 **/
@Data
public class LkWeChatBusinessLicenseInfo implements Serializable {

    private static final long serialVersionUID = 1582941630439552458L;

    private String businessLicenseCopy;

    private String businessLicenseNumber;

    private String merchantName;

    private String legalPerson;

    private String companyAddress;

    private String businessTime;

    public LkWeChatBusinessLicenseInfo(){
        this.businessLicenseCopy = "1";
        this.businessLicenseNumber = "2";
        this.merchantName = "3";
        this.legalPerson = "4";
        this.companyAddress = "5";
        this.businessTime = "6";
    }
}

2.将实体转换为json字符串，看看未转换前的效果

System.out.println(JSONObject.toJSONString(new LkWeChatBusinessLicenseInfo()));

{
    "businessLicenseCopy":"1",
    "businessLicenseNumber":"2",
    "businessTime":"6",
    "companyAddress":"5",
    "legalPerson":"4",
    "merchantName":"3"
}

3.我们要转换为带下划线的key，例如把businessLicenseCopy转换为business_license_copy

我们需要修改实体，加上注解@JSONField

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;

import java.io.Serializable;

/**
 * @类名 WeChatBusinessLicenseInfo
 * @描述 营业执照/登记证书信息（测试用）
 * @版本 1.0
 * @创建人 XuKang
 * @创建时间 2021/12/24 10:43
 **/
@Data
public class LkWeChatBusinessLicenseInfo implements Serializable {

    private static final long serialVersionUID = 1582941630439552458L;

    @JSONField(name = "business_license_copy")
    private String businessLicenseCopy;

    @JSONField(name = "business_license_number")
    private String businessLicenseNumber;

    @JSONField(name = "merchant_name")
    private String merchantName;

    @JSONField(name = "legal_person")
    private String legalPerson;

    @JSONField(name = "company_address")
    private String companyAddress;

    @JSONField(name = "business_time")
    private String businessTime;

    public LkWeChatBusinessLicenseInfo(){
        this.businessLicenseCopy = "1";
        this.businessLicenseNumber = "2";
        this.merchantName = "3";
        this.legalPerson = "4";
        this.companyAddress = "5";
        this.businessTime = "6";
    }

}

4.加上注解后打印转换后的json

System.out.println(JSONObject.toJSONString(new LkWeChatBusinessLicenseInfo()));

{
    "business_license_copy":"1",
    "business_license_number":"2",
    "business_time":"6",
    "company_address":"5",
    "legal_person":"4",
    "merchant_name":"3"
}

三、字段排序

1.我们输出打印的json是这样的

{
    "business_license_copy":"1",
    "business_license_number":"2",
    "business_time":"6",
    "company_address":"5",
    "legal_person":"4",
    "merchant_name":"3"
}

我们想按照一定的顺序重新排序key

2.在@JSONField注解加上排序ordinal

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;

import java.io.Serializable;

/**
 * @类名 WeChatBusinessLicenseInfo
 * @描述 营业执照/登记证书信息（测试用）
 * @版本 1.0
 * @创建人 XuKang
 * @创建时间 2021/12/24 10:43
 **/
@Data
public class LkWeChatBusinessLicenseInfo implements Serializable {

    private static final long serialVersionUID = 1582941630439552458L;

    @JSONField(name = "business_license_copy",ordinal = 1)
    private String businessLicenseCopy;

    @JSONField(name = "business_license_number",ordinal = 2)
    private String businessLicenseNumber;

    @JSONField(name = "merchant_name",ordinal = 3)
    private String merchantName;

    @JSONField(name = "legal_person",ordinal = 4)
    private String legalPerson;

    @JSONField(name = "company_address",ordinal = 5)
    private String companyAddress;

    @JSONField(name = "business_time",ordinal = 6)
    private String businessTime;

    public LkWeChatBusinessLicenseInfo(){
        this.businessLicenseCopy = "1";
        this.businessLicenseNumber = "2";
        this.merchantName = "3";
        this.legalPerson = "4";
        this.companyAddress = "5";
        this.businessTime = "6";
    }

}

3.输出打印转换后的实体：

System.out.println(JSONObject.toJSONString(new LkWeChatBusinessLicenseInfo()));

{
    "business_license_copy":"1",
    "business_license_number":"2",
    "merchant_name":"3",
    "legal_person":"4",
    "company_address":"5",
    "business_time":"6"
}

四、总结

重命名除@JSONField，还有@JsonProperty、@SerializedName；

@JsonProperty主要用于入参转换，和Json字符串序列化为Java对象；

@SerializedName 改变了默认序列化和默认反序列化的字段取值；