<dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.66</version> </dependency>
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"
}
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"
}
小结：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；
应用场景：
当我们在与前端进行交互时，前端想要的字段与我们提供的字段名不同，这时候一种解决方案是修改实体类，但如果该实体类应用的比较多，那改起来的代价太大，因此，可以使用注解@JSONField来实现替换效果，用法如下：
@JSONField(name = "size_new") private int size;
JSON（与下述JSON字符串内容一致）
{
size: 5,
weight: 10,
colour: "red"
}实体类（AppleDO.java)
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.annotation.JSONField;
public class AppleDO {
@JSONField(name = "size_new")
private int size;
@JSONField(name = "weight_new")
private int weight;
@JSONField(name = "colour_new")
private String colour;
public int getSize() {
return size;
}
public void setSize(int size) {
this.size = size;
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public String getColour() {
return colour;
}
public void setColour(String colour) {
this.colour = colour;
}
}执行代码
public static void main(String[] args) {
String json = "{\n" +
" size_new: 5,\n" +
" weight_new: 10,\n" +
" colour_new: \"red\",\n" +
"}";
AppleDO appleDO = JSON.parseObject(json, AppleDO.class);
System.out.println(appleDO.getSize());
System.out.println(appleDO.getWeight());
System.out.println(appleDO.getColour());
}运行结果
源码中的序列化和反序列化默认值均为true，则默认情况下是允许该字段序列化和反序列化的，如下：
boolean serialize() default true; boolean deserialize() default true;
使用方法（以下不支持序列化，支持反序列化）
@JSONField(name = "size_new", serialize = false, deserialize = true) private int size;
当我们的某些字段为空值时，我们仍希望将此字段返回到前端（该配置可以返回带有空字段的字符串，但是当字段为基本数据类型时无效，须将其转换为包装类）
@JSONField(serialzeFeatures= SerializerFeature.WriteMapNullValue)
将Java对象转换为JSON格式，转换后的字段顺序会根据首字母来排序，亦可通过如下方式来指定字段顺序：
@JSONField(name = "size_new", ordinal = 3) private int size; @JSONField(name = "weight_new", ordinal = 1) private int weight; @JSONField(name = "colour_new", ordinal = 2) private String colour;
执行代码
AppleDO apple = new AppleDO();
apple.setSize(6);
apple.setWeight(12);
apple.setColour("green");
String appleStr = JSON.toJSONString(apple);
System.out.println(appleStr);加ordinal参数之前运行结果
加ordinal参数之后运行结果
