json解析的三种方式

Json 是什么？

json是一种用于进行网络数据传输的格式，使用广泛。在json中有JsonObject和JsonArray两种形式

当你看到以 { 开始的说明这是一个JsonObject
如果是看到以 [ 开始的说明是一个JsonArray

1. json 数据在键/值对中
2. 数据由逗号分隔
3. 花括号{}保存对象
4. 方括号[]保存数组

json对象
JsonObject(json对象)在花括号{}中，json对象包括多个键/值对，例如：

{"name":"zhangsan" , "age":25}

json数组
JsonArray(json数组)在方括号[]中，数组也可以包括多个对象，例如：

{"student":[{"name":"zhangsan" , "age":12},{"name":"lisi" , "age":13},{"name":"wangwu" , "age":14}]}

---

###Android中如何解析json
前面铺垫了这么久，现在才是这篇文章的重点，如何在android中对json数据进行解析。在接下来的解析过程中我们分别使用三种方式对下面的json数据进行解析。

---

json数据

json1 = {"name":"sam","age":18,"weight":60} //只包含json对象
json2 = [12,13,15] //只包含json数组
json3 = [{"name":"sam","age":18},{"name":"leo","age":19},{"name":"sky", "age":20}] //含有对象的json数组

---

解析的方式

1. 使用util包中的JsonReader进行解析
2. 使用org.json包中的JSONObject和JSONArray进行解析
3. 使用谷歌的Gson包进行解析

---

###对json1分别用三种方式进行解析

json1 = {"name":"sam","age":18,"weight":60}

• JsonReader方式

  JsonReader reader = new JsonReader(new InputStreamReader(json1));
  try{
      reader.beginObject();
      while(reader.hasNext()){
          String keyName = reader.nextName();
          if("name".equals(keyName)){
          String name = reader.nextString();
          }else if("age".equals(keyName)){
              int age = reader.nextInt();
          }else if("weight".equals(keyName)){
              int weight = reader.nextInt();
          }
      }
      reader.endObject();
  }
  finally{
      reader.close();
  }

• JSONObject方式和JSONArray方式

  JSONObject jsonObj = new JSONObject(json1);
  String name = jsonObj.optString("name");
  int age = jsonObj.optInt("age");
  int weight = jsonObj.optInt("weight");

• Gson方式

  Gson gson = new Gson();
  Student student = gson.fromJson(json1, Student.class);

如果希望采用这种方式进行解析，那么需要把json所有的对象都需要在bean中写出来，而且名字也需要和返回的对象名一样。类似于：

private String name;
    private int age;
    private int weight;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getWeight() {
        return weight;
    }

    public void setWeight(int weight) {
        this.weight = weight;
    }

---

###对json2进行解析

json2 = [12,13,15]

• JsonReader方式

  JsonReader reader = new JsonReader(new InputStreamReader(json2));
  try {
      List<Integer> ages = new ArrayList<Integer>();
      reader.beginArray();
      while (reader.hasNext()) {
          ages.add(reader.nextInt());
      }
      reader.endArray();
  } 
  finally {
      reader.close();
  }

• JsonObject和JsonArray方式

  JSONArray jsonArray = new JSONArray(json2);
  for (int i= 0; i < jsonArray.length(); i++) {
      int age = jsonArray.optInt(i); 
  }

• Gson方式
  对于Json数组我们可以解析成数组或者list形式

  • 数组形式

    Gson gson = new Gson();
    int[] ages = gson.fromJson(json2, int[].class);

  • list形式

    Gson gson = new Gson();
    List<Integer> ages = gson.fromJson(json2, new TypeToken<List<Integer>>(){}.getType);

###对json3解析

json3 = [{"name":"sam","age":18},{"name":"leo","age":19},{"name":"sky", "age":20}]

• jsonReader方式

  JsonReader reader = new JsonReader(new InputStreamReader(json3));
  try {
      List<Object> ages = new ArrayList<Object>();
      reader.beginArray();
      while (reader.hasNext()) {
          reader.biginObject();
          while(reader.hasNext()){
              String keyName = reader.nextName();
              if("name".equals(keyName)){
              String name = reader.nextString();
              }else if("age".equals(keyName)){
                  int age = reader.nextInt();
              }else if("weight".equals(keyName)){
                  int weight = reader.nextInt();
              }
          }
          reader.endObject();
      }
      reader.endArray();
  } 
  finally {
      reader.close();
  }

• JsonObject和JsonArray方式

  JSONArray jsonArray = new JSONArray(json3);
  for (int i= 0; i < jsonArray.length(); i++) {
      JSONObject jsonObject = jsonArray.optJSONObject(i);
      String name = jsonObject.optString("name");
      int age = jsonObject.optInt("age");
  }

• Gson方式

• 我们直接解析成list方式

  Gson gson = new Gson();
  List<Student> students = gson.fromJson(json3, new TypeToke<List<Student>>(){}.getType);

###总结

在平时的解析过程过程中，我是很少采用第一种方式，更多的是第二种方式和第三种方式相互结合起来.Gson在解析那种对象较少的情况下还是比较方便，如果对象较多，那么写bean的时候，那感觉就不说了，第二种方式其实挺不错的。

---

###最后
附上一个平时解析的真实案例：
json数据：

{
"date": "20171210",
"stories": [
{
"images": [
"https://pic1.zhimg.com/v2-f7ef9c4491a77fd0921b39d0ce71ff9c.jpg"
],
"type": 0,
"id": 9660440,
"ga_prefix": "121016",
"title": "《塞尔达传说：旷野之息》获 TGA 2017 年度最佳游戏，名至实归"
},
{
"images": [
"https://pic1.zhimg.com/v2-e88b85b62e17b2f7bcc643c1e2161158.jpg"
],
"type": 0,
"id": 9660342,
"ga_prefix": "121014",
"title": "该用的东西永远找不到、永远乱糟糟，其实厨房收纳有技巧"
},
{
"images": [
"https://pic2.zhimg.com/v2-c8411ecbb96cdaacacc76402fc134a85.jpg"
],
"type": 0,
"id": 9659553,
"ga_prefix": "121012",
"title": "大误 · 在魔法次元你主修什么？"
},
{
"images": [
"https://pic1.zhimg.com/v2-4b403aab5f1728ca8dcc81cb3b8d7bc0.jpg"
],
"type": 0,
"id": 9660290,
"ga_prefix": "121011",
"title": "刚学开车，要是不注意这些经验，怕是要「送人头」的"
},
{
"images": [
"https://pic2.zhimg.com/v2-5163ab7218452fced95c39b427b320a1.jpg"
],
"type": 0,
"id": 9660389,
"ga_prefix": "121010",
"title": "「商业模式」，见过无数次，从来也没人解释这词什么意思"
},
{
"images": [
"https://pic3.zhimg.com/v2-a1d9bc75eb5f833c7dd7a110ece0c6d6.jpg"
],
"type": 0,
"id": 9659495,
"ga_prefix": "121009",
"title": "后来我才知道，这个世上并不存在没有任何「残」「障」的人"
},
{
"images": [
"https://pic3.zhimg.com/v2-85aad5f9d12407b768b72c48d4994686.jpg"
],
"type": 0,
"id": 9660420,
"ga_prefix": "121008",
"title": "本周热门精选 · 不安的时代"
},
{
"images": [
"https://pic1.zhimg.com/v2-3b3598e906c694016ae6b3ad82d7c300.jpg"
],
"type": 0,
"id": 9660432,
"ga_prefix": "121007",
"title": "有哪些设计很棒的学校宿舍楼？"
},
{
"images": [
"https://pic4.zhimg.com/v2-92c3e744296c1785dd8121269be9a5f7.jpg"
],
"type": 0,
"id": 9660422,
"ga_prefix": "121007",
"title": "在微博就能找到梅西的年代，信虫还在用最原始的方法追星"
},
{
"images": [
"https://pic1.zhimg.com/v2-38b60458db353bc0fca4b640e7f974a0.jpg"
],
"type": 0,
"id": 9659975,
"ga_prefix": "121007",
"title": "消失中的线下服装市场：一个时代已远去"
},
{
"images": [
"https://pic3.zhimg.com/v2-cd12dc594ecef927aabf1f1fa98e2bc2.jpg"
],
"type": 0,
"id": 9660412,
"ga_prefix": "121006",
"title": "瞎扯 · 如何正确地吐槽"
}
],
"top_stories": [
{
"image": "https://pic3.zhimg.com/v2-4a898c5475f6476d3b8378165c27634e.jpg",
"type": 0,
"id": 9660420,
"ga_prefix": "121008",
"title": "本周热门精选 · 不安的时代"
},
{
"image": "https://pic2.zhimg.com/v2-0df5956d2c24f8b76f5198227714680d.jpg",
"type": 0,
"id": 9660189,
"ga_prefix": "120916",
"title": "赚了钱，企业家们该不该扶贫？"
},
{
"image": "https://pic4.zhimg.com/v2-557ca00c7e34c6ed672ea5b9e5d395a3.jpg",
"type": 0,
"id": 9660049,
"ga_prefix": "120910",
"title": "把一个人丢进蚊子窝里会死，但却不是因为失血而亡……"
},
{
"image": "https://pic2.zhimg.com/v2-910ace866bcf0a8a370f95f082403489.jpg",
"type": 0,
"id": 9659771,
"ga_prefix": "120909",
"title": "只见人进，不见人归：传说中的「死亡谷」"
},
{
"image": "https://pic3.zhimg.com/v2-15949b00edcf48c610499dfc096b85be.jpg",
"type": 0,
"id": 9659975,
"ga_prefix": "121007",
"title": "消失中的线下服装市场：一个时代已远去"
}
]
}

bean:

package com.example.bbw.openzz.Model.ZhiHuDaily;


import java.util.List;

/**
 * Created by bbw on 2017/10/26.
 * @author bbw
 */

public class ZhiHuDaily {

    private List<StoryBean> storiesList;

    public List<StoryBean> getStoriesList() {
        return storiesList;
    }

    public void setStoriesList(List<StoryBean> storiesList) {
        this.storiesList = storiesList;
    }

    public static class StoryBean {

        private String title;
        private String images;
        private int id;

        public StoryBean(String title, String images, int id) {
            this.title = title;
            this.images = images;
            this.id = id;
        }

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public String getImages() {
            return images;
        }

        public void setImages(String images) {
            this.images = images;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }
    }
}

解析：

public static List<ZhiHuDaily.StoryBean> handleZhuHuDailyLatest(String responseText) throws JSONException {

           JSONObject jsonObject = new JSONObject(responseText);
           JSONArray jsonArray = jsonObject.getJSONArray("stories");
           List<ZhiHuDaily.StoryBean> storyBeansList = new ArrayList<>();
           for (int i=0;i<jsonArray.length();i++){
               JSONObject newsInJson = jsonArray.getJSONObject(i);
               int id = newsInJson.optInt("id");
               String title = newsInJson.optString("title");
               String image = "";
               if (newsInJson.has("images")) {
                   image = (String) newsInJson.getJSONArray("images").get(0);

               }
               ZhiHuDaily.StoryBean news = new ZhiHuDaily.StoryBean(title,image,id);
               storyBeansList.add(news);
           }
       return storyBeansList;
   }