如何在Java中使用Gson解析含billingInformation的嵌套JSON文件

方案一：手动逐层解析（适配现有代码逻辑） #

不需要移除billingInformation字段，只需先从根JSON对象中提取该字段对应的子对象，再逐层解析嵌套内容：

Reader reader = new BufferedReader(Files.newBufferedReader(Paths.get(bill)));
// 获取根JSON对象
JsonObject rootObj = JsonParser.parseReader(reader).getAsJsonObject();
// 提取billingInformation子对象
JsonObject billingInfoObj = rootObj.getAsJsonObject("billingInformation");

// 解析Taxes
Taxes taxes = new Taxes();
JsonObject taxesObj = billingInfoObj.getAsJsonObject("taxes");
taxes.setGST(taxesObj.get("gst").getAsDouble());
taxes.setHST(taxesObj.get("hst").getAsDouble());

// 解析billTo
BillTo billTo = new BillTo();
JsonObject billToObj = billingInfoObj.getAsJsonObject("billTo");
billTo.setName(billToObj.get("name").getAsString());
billTo.setAddress(billToObj.get("address").getAsString());
billTo.setPhoneNumber(billToObj.get("phoneNumber").getAsString());

// 解析salesAgent
SalesAgent salesAgent = new SalesAgent();
JsonObject agentObj = billingInfoObj.getAsJsonObject("salesAgent");
salesAgent.setName(agentObj.get("name").getAsString());
salesAgent.setAgentCode(agentObj.get("agentCode").getAsInt());

// 解析items及嵌套的item列表
Items items = new Items();
JsonObject itemsObj = billingInfoObj.getAsJsonObject("items");
items.setCurrency(itemsObj.get("currency").getAsString());

JsonArray itemArray = itemsObj.getAsJsonArray("item");
List<Item> itemList = new ArrayList<>();
for (JsonElement elem : itemArray) {
    JsonObject itemObj = elem.getAsJsonObject();
    Item item = new Item();
    item.setHsnCode(itemObj.get("hsnCode").getAsString());
    item.setDescription(itemObj.get("description").getAsString());
    item.setOriginCountry(itemObj.get("originCountry").getAsString());
    item.setQuantity(itemObj.get("quantity").getAsInt());
    item.setUnitPrice(itemObj.get("unitPrice").getAsDouble());
    itemList.add(item);
}
items.setItem(itemList);

方案二：实体类自动映射（推荐，简洁高效） #

定义与JSON结构完全对应的实体类，利用Gson的自动反序列化功能，无需手动逐层解析：

1. 定义所有嵌套实体类 #

根实体类 BillRoot

public class BillRoot {
    private BillingInformation billingInformation;

    // Getter & Setter
    public BillingInformation getBillingInformation() {
        return billingInformation;
    }

    public void setBillingInformation(BillingInformation billingInformation) {
        this.billingInformation = billingInformation;
    }
}

BillingInformation 类

public class BillingInformation {
    private Taxes taxes;
    private BillTo billTo;
    private SalesAgent salesAgent;
    private Items items;

    // Getter & Setter 需为每个字段生成
}

Taxes 类

public class Taxes {
    private double gst;
    private double hst;

    // Getter & Setter
    public double getGst() { return gst; }
    public void setGst(double gst) { this.gst = gst; }
    public double getHst() { return hst; }
    public void setHst(double hst) { this.hst = hst; }
}

BillTo 类

public class BillTo {
    private String name;
    private String address;
    private String phoneNumber;

    // Getter & Setter
}

SalesAgent 类

public class SalesAgent {
    private String name;
    private int agentCode;

    // Getter & Setter
}

Items 类

public class Items {
    private List<Item> item;
    private String currency;

    // Getter & Setter
}

Item 类

public class Item {
    private String hsnCode;
    private String description;
    private String originCountry;
    private int quantity;
    private double unitPrice;

    // Getter & Setter
}

2. 自动反序列化代码 #

Gson gson = new Gson();
Reader reader = new BufferedReader(Files.newBufferedReader(Paths.get(bill)));
// 直接将JSON解析为根实体类对象
BillRoot billRoot = gson.fromJson(reader, BillRoot.class);

// 直接获取各层级数据
BillingInformation billingInfo = billRoot.getBillingInformation();
Taxes taxes = billingInfo.getTaxes();
BillTo billTo = billingInfo.getBillTo();
// 其他数据可通过对应getter方法获取

注意事项 #

• 实体类字段名需与JSON中的键大小写完全匹配，若需自定义字段名，可使用@SerializedName("JSON键名")注解指定
• 字段若可能为null，建议使用包装类（如Double代替double）避免空指针异常
• 所有实体类需提供默认无参构造方法（Gson依赖此实例化对象）

内容的提问来源于stack exchange，提问作者user19204430