Java物件轉Json,關於@JSONField物件欄位重新命名和順序問題

2022-08-30 14:03:51

Java物件轉Json,@JSONField物件欄位重新命名和順序

一、引入maven依賴

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

二、欄位重新命名

1.建立一個測試實體

import lombok.Data; 
import java.io.Serializable;
 
/**
 * @類名 WeChatBusinessLicenseInfo
 * @描述 營業執照/登記證書資訊（測試用）
 * @版本 1.0
 * @建立人 XuKang
 * @建立時間 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.將實體轉換為json字串，看看未轉換前的效果

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

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

3.我們要轉換為帶下劃線的key，例如把businessLicenseCopy轉換為business_license_copy

我們需要修改實體，加上註解@JSONField

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;
import java.io.Serializable;
 
/**
 * @類名 WeChatBusinessLicenseInfo
 * @描述 營業執照/登記證書資訊（測試用）
 * @版本 1.0
 * @建立人 XuKang
 * @建立時間 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.加上註解後列印轉換後的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、欄位排序

1.我們輸出列印的json是這樣的

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

我們想按照一定的順序重新排序key

2.在@JSONField註解加上排序ordinal

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;
import java.io.Serializable;
 
/**
 * @類名 WeChatBusinessLicenseInfo
 * @描述 營業執照/登記證書資訊（測試用）
 * @版本 1.0
 * @建立人 XuKang
 * @建立時間 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.輸出列印轉換後的實體：

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"
}

小結：重新命名除@JSONField，還有@JsonProperty、@SerializedName；@JsonProperty主要用於入參轉換，和Json字串序列化為Java物件；@SerializedName 改變了預設序列化和預設反序列化的欄位取值；

@JSONField註解常用的使用場景

應用場景：

當我們在與前端進行互動時，前端想要的欄位與我們提供的欄位名不同，這時候一種解決方案是修改實體類，但如果該實體類應用的比較多，那改起來的代價太大，因此，可以使用註解@JSONField來實現替換效果，用法如下：

@JSONField(name = "size_new")
private int size;

一、JSON內容與實體類，@JSONField常規寫法

JSON（與下述JSON字串內容一致）

{
    size: 5,
    weight: 10,
    colour: "red"
}

實體類（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;
    }
}

二、JSON字串轉對應Java物件

執行程式碼

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());
}

執行結果

三、支援序列化和反序列化

原始碼中的序列化和反序列化預設值均為true，則預設情況下是允許該欄位序列化和反序列化的，如下：

boolean serialize() default true;
boolean deserialize() default true;

使用方法（以下不支援序列化，支援反序列化）

@JSONField(name = "size_new", serialize = false, deserialize = true)
private int size;

當我們的某些欄位為空值時，我們仍希望將此欄位返回到前端（該設定可以返回帶有空欄位的字串，但是當欄位為基本資料型別時無效，須將其轉換為包裝類）

@JSONField(serialzeFeatures= SerializerFeature.WriteMapNullValue)

四、指定欄位順序

將Java物件轉換為JSON格式，轉換後的欄位順序會根據首字母來排序，亦可通過如下方式來指定欄位順序：

@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;

執行程式碼

AppleDO apple = new AppleDO();
apple.setSize(6);
apple.setWeight(12);
apple.setColour("green");
String appleStr = JSON.toJSONString(apple);
System.out.println(appleStr);

加ordinal引數之前執行結果