在 Android 中解析嵌套的 JSON 对象

Posted 2023-02-26

【中文标题】在 Android 中解析嵌套的 JSON 对象

【英文标题】：Parsing nested JSON object in Android

【发布时间】：2011-08-24 13:47:15

【问题描述】：

我正在尝试解析一个 JSON 对象，其中一部分如下所示：

"offer":
    "category":"Salon",
    "description":"Use this offer now to enjoy this great Salon at a 20% discount. ",
    "discount":"20",
    "expiration":"2011-04-08T02:30:00Z",
    "published":"2011-04-07T12:00:33Z",
    "rescinded_at":null,
    "title":"20% off at Jun Hair Salon",
    "valid_from":"2011-04-07T12:00:31Z",
    "valid_to":"2011-04-08T02:00:00Z",
    "id":"JUN_HAIR_1302177631",
    "business":
        "name":"Jun Hair Salon",
        "phone":"2126192989",
        "address":
            "address_1":"12 Mott St",
            "address_2":null,
            "city":"New York",
            "cross_streets":"Chatham Sq & Worth St",
            "state":"NY",
            "zip":"10013"
        
    ,

等等……

到目前为止，我可以通过做这样的事情来非常简单地解析：

JSONObject jObject = new JSONObject(content);
JSONObject offerObject = jObject.getJSONObject("offer");
String attributeId = offerObject.getString("category");
System.out.println(attributeId);

String attributeValue = offerObject.getString("description");
System.out.println(attributeValue);

String titleValue = offerObject.getString("title");
System.out.println(titleValue);`

但是当我尝试使用 'name:' 时，它不起作用。

我试过了：

JSONObject businessObject = jObject.getJSONObject("business");
String nameValue = businesObject.getString("name");
System.out.println(nameValue);

当我尝试这样做时，我得到“未找到 JSONObject [business]”。

当我尝试时：

String nameValue = offerObject.getString("name");
System.out.println(nameValue);`

正如预期的那样，我得到“未找到 JSONObject [name]”。

我在这里做错了什么？我缺少一些基本的东西......

【问题讨论】：

嗨，我刷新了以下页面并得到了解决方案***.com/questions/5986123/…

【参考方案1】：

这里是单行解决方案

String myString = myJsonObject.getJSONObject("offer").getJSONObject("business").getString("name");

【参考方案2】：

请注意，将 JSON 序列化/反序列化到 Java 对象/从 Java 对象序列化/反序列化不必“手动”完成。 GSON 和 Jackson 之类的库让这一切变得非常简单。

import java.text.DateFormat;
import java.util.Date;
import com.google.gson.FieldNamingPolicy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class Foo

  static String jsonInput = 
    "" + 
      "\"offer\":" + 
        "\"category\":\"Salon\"," + 
        "\"description\":\"Use this offer now to enjoy this great Salon at a 20% discount. \"," + 
        "\"discount\":\"20\"," + 
        "\"expiration\":\"2011-04-08T02:30:00Z\"," + 
        "\"published\":\"2011-04-07T12:00:33Z\"," + 
        "\"rescinded_at\":null," + 
        "\"title\":\"20% off at Jun Hair Salon\"," + 
        "\"valid_from\":\"2011-04-07T12:00:31Z\"," + 
        "\"valid_to\":\"2011-04-08T02:00:00Z\"," + 
        "\"id\":\"JUN_HAIR_1302177631\"," + 
        "\"business\":" + 
          "\"name\":\"Jun Hair Salon\"," + 
          "\"phone\":\"2126192989\"," + 
          "\"address\":" + 
            "\"address_1\":\"12 Mott St\"," + 
            "\"address_2\":null," + 
            "\"city\":\"New York\"," + 
            "\"cross_streets\":\"Chatham Sq & Worth St\"," + 
            "\"state\":\"NY\"," + 
            "\"zip\":\"10013\"" + 
          "" + 
        "" + 
      "" + 
    "";

public static void main(String[] args) throws Exception
  
    GsonBuilder gsonBuilder = new GsonBuilder();
    // gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
    gsonBuilder.setDateFormat(DateFormat.LONG);
    Gson gson = gsonBuilder.create();
    OfferContainer offerContainer = gson.fromJson(jsonInput, OfferContainer.class);
    System.out.println(offerContainer);
  


class OfferContainer

  private Offer offer;

@Override
  public String toString()
  
    return offer.toString();
  


class Offer

  private Category category;
  private String description;
  private String discount;
  private Date expiration;
  private Date published;
  private String rescinded_at;
  private String title;
  private Date valid_from;
  private Date valid_to;
  private String id;
  private Business business;

@Override
  public String toString()
  
    return String.format(
            "[Offer: category=%1$s, description=%2$s, discount=%3$s, expiration=%4$s, published=%5$s, rescinded_at=%6$s, title=%7$s, valid_from=%8$s, valid_to=%9$s, id=%10$s, business=%11$s]",
            category, description, discount, expiration, published, rescinded_at, title, valid_from, valid_to, id,
            business);
  


enum Category

  Salon


class Business

  private String name;
  private String phone;
  private Address address;

@Override
  public String toString()
  
    return String.format(
        "[Business: name=%1$s, phone=%2$s, address=%3$s]",
        name, phone, address);
  


class Address

  private String address_1;
  private String address_2;
  private String city;
  private String cross_streets;
  private String state;
  private String zip;

@Override
  public String toString()
  
    return String.format(
        "[Address: address_1=%1$s, address_2=%2$s, city=%3$s, cross_streets=%4$s, state=%5$s, zip=%6$s]",
        address_1, address_2, city, cross_streets, state, zip);
  

请注意，可以使用 FieldNamingPolicy 轻松地将属性名称从 JSON 映射到 Java 代码。不幸的是，LOWER_CASE_WITH_UNDERSCORES 策略不适用于“address_1”等 JSON 属性名称。

如果关注 JSON 处理的性能，请查看 Jackson Vs. Gson 和 http://www.cowtowncoder.com/blog/archives/2011/01/entry_437.html

【讨论】：

哇，这东西真棒。非常感谢。本来会接受我自己的答案，但现在我不太确定.... ;)

我忘了提几件事。 1. GSON 内置于 android 3.0+。只需使用 AndroidJsonFactory。 2. HTC 人员介绍了在某些 HTC 设备上使用 GSON 的错误。解决方法是只使用 jarjar 将 GSON 代码移动到另一个包。见code.google.com/p/google-gson/issues/detail?id=255

是一个单独的问题，但是从 HttpURLConnection 获取 json 字符串的最简单方法是什么？

@Programmer Bruce - 我如何将 json 数组放入我的 String.format 方法中？

我不知道那是什么意思。您是否尝试序列化 Java 对象以生成 JSON 字符串？

【参考方案3】：

好吧，我是个白痴。这行得通。

JSONObject businessObject = offerObject.getJSONObject("business");
String nameValue = businessObject.getString("name");
System.out.println(nameValue);

如果我在发帖前只想两秒钟……天哪！

【讨论】：

哈哈，很高兴你知道了！不要忘记接受你自己的答案，我认为有某种虚荣徽章;-)