使用Gson解析json数据

系统管理员 2022-07-14 03:26 293阅读 0赞

# Gson解析系列阅读 #

*  [Gson使用指南][Gson]
 *  [使用Gson解析复杂的JSON数据][Gson_JSON]
 *  [使用Gson解析json数据][Gson_json]
 *  [Gson全解析][Gson 1]
 *  [搞定Gson泛型封装][Gson 2]
 *  [简单新闻客户端][Link 1]

# **1. json** #

Json 全称 JavaScript Object Natation ，用来描述数据结构，它是基于纯文本的数据格式，是一种轻量级的数据交换格式。广泛应用于服务端与客户端的数据交互。

# **2. 格式** #

*  Json 以key－value的形式存储数据
 *  Key的取值为String类型
 *  Value的取值为String，boolean，Number，数组，Object，null
 *  Json串以\{ 开始，以 \} 结尾
 *  Json 串中数组是以 \[ 开始，以 \] 结尾
 *  Json串中Object是以 \{ 开始，以 \} 结尾

# **3. 原生解析** #

JSONObject root = new JSONObject(response);
    JSONArray jsonArray = root.getJSONArray("appinfo");
    JSONObject jsonObject = jsonArray.getJSONObject(0);
    String des = jsonObject.getString("des");
    jsonObject.optString()

[
        {
            "infos": [ { "name1": "休闲", "name2": "棋牌", "name3": "益智", "url1": "image/category_game_0.jpg", "url2": "image/category_game_1.jpg", "url3": "image/category_game_2.jpg" }, { "name1": "射击", "name2": "体育", "name3": "儿童", "url1": "image/category_game_3.jpg", "url2": "image/category_game_4.jpg", "url3": "image/category_game_5.jpg" }, { "name1": "网游", "name2": "角色", "name3": "策略", "url1": "image/category_game_6.jpg", "url2": "image/category_game_7.jpg", "url3": "image/category_game_8.jpg" }, { "name1": "经营", "name2": "竞速", "name3": "", "url1": "image/category_game_9.jpg", "url2": "image/category_game_10.jpg", "url3": "" } ],
            "title": "游戏" },
        {
            "infos": [ { "name1": "浏览器", "name2": "输入法", "name3": "健康", "url1": "image/category_app_0.jpg", "url2": "image/category_app_1.jpg", "url3": "image/category_app_2.jpg" }, { "name1": "效率", "name2": "教育", "name3": "理财", "url1": "image/category_app_3.jpg", "url2": "image/category_app_4.jpg", "url3": "image/category_app_5.jpg" }, { "name1": "阅读", "name2": "个性化", "name3": "购物", "url1": "image/category_app_6.jpg", "url2": "image/category_app_7.jpg", "url3": "image/category_app_8.jpg" }, { "name1": "资讯", "name2": "生活", "name3": "工具", "url1": "image/category_app_9.jpg", "url2": "image/category_app_10.jpg", "url3": "image/category_app_11.jpg" }, { "name1": "出行", "name2": "通讯", "name3": "拍照", "url1": "image/category_app_12.jpg", "url2": "image/category_app_13.jpg", "url3": "image/category_app_14.jpg" }, { "name1": "社交", "name2": "影音", "name3": "安全", "url1": "image/category_app_15.jpg", "url2": "image/category_app_16.jpg", "url3": "image/category_app_17.jpg" } ],
            "title": "应用" }
    ]

![json][]

public class CategoryInfoBean { 
        public String  title;    // title
        public String  name1;    // 休闲
        public String  name2;    // 棋牌
        public String  name3;    // 益智
        public String  url1;     // image/category_game_0.jpg
        public String  url2;     // image/category_game_1.jpg
        public String  url3;     // image/category_game_2.jpg
        public boolean isTitle;   // 自己添加的一个属性,确定是否是title
    }

List<CategoryInfoBean> categoryInfoBeans = new ArrayList<CategoryInfoBean>();
    try {
        JSONArray rootJsonArray = new JSONArray(jsonString);
        // 遍历jsonArray
        for (int i = 0; i < rootJsonArray.length(); i++) {
            JSONObject itemJsonObject = rootJsonArray.getJSONObject(i);
            String title = itemJsonObject.getString("title");
            CategoryInfoBean titleBean = new CategoryInfoBean();
            titleBean.title = title;
            titleBean.isTitle = true;
            categoryInfoBeans.add(titleBean);
            JSONArray infosJsonArray = itemJsonObject.getJSONArray("infos");
            // 遍历infosJsonArray
            for (int j = 0; j < infosJsonArray.length(); j++) {
                JSONObject infoJsonObject = infosJsonArray.getJSONObject(j);
                String name1 = infoJsonObject.getString("name1");
                String name2 = infoJsonObject.getString("name2");
                String name3 = infoJsonObject.getString("name3");
                String url1 = infoJsonObject.getString("url1");
                String url2 = infoJsonObject.getString("url2");
                String url3 = infoJsonObject.getString("url3");
    
                CategoryInfoBean infoBean = new CategoryInfoBean();
                infoBean.name1 = name1;
                infoBean.name2 = name2;
                infoBean.name3 = name3;
                infoBean.url1 = url1;
                infoBean.url2 = url2;
                infoBean.url3 = url3;
                categoryInfoBeans.add(infoBean);
            }
        }

public List<CategoryInfo> parseData(String result) {
            if (!TextUtils.isEmpty(result)) {
                try {
                    categoryInfoList = new ArrayList<CategoryInfo>();
                    JSONArray jsonArray=new JSONArray(result);
    
                    for (int i = 0; i < jsonArray.length(); i++) {
                        JSONObject jsonObject=jsonArray.getJSONObject(i);
                        CategoryInfo categoryInfo=new CategoryInfo();
                        if (jsonObject.has("title")) {
                            categoryInfo.setTitle(jsonObject.getString("title"));
                            categoryInfo.setTitle(true);
                            categoryInfoList.add(categoryInfo);
                        }
                        if (jsonObject.has("info")) {
                            categoryInfo.setName1(jsonObject.getString("name1"));
                            categoryInfo.setName2(jsonObject.getString("name2"));
                            categoryInfo.setName3(jsonObject.getString("name3"));
                            categoryInfo.setUrl1(jsonObject.getString("url1"));
                            categoryInfo.setUrl1(jsonObject.getString("url2"));
                            categoryInfo.setUrl1(jsonObject.getString("url3"));
                            categoryInfo.setTitle(false);
                            categoryInfoList.add(categoryInfo);
                        }
                    }
                    return categoryInfoList;
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
            return null;
        }

![json][json 1]

# **4. Gson格式化** #

将 java 对象 格式化为 Json 字符串.

实现步骤 :

获得需要的对象:

Student stu = new Student();
    stu.setName("张三");
    stu.setAge(18);
    stu.setSex(true);

格式化

Gson gson = new Gson();
    //将 对象 转化成 json 字符串
    String json = gson.toJson(stu)

# **5. Gson解析** #

遇到\[ \]就解析成集合，遇到\{ \}就解析成对象，遇到”“就解析成一个对应的基本数据类型

{
        "data": [ { "children": [ { "id": 10007, "title": "北京", "type": 1, "url": "/10007/list_1.json" }, { "id": 10006, "title": "中国", "type": 1, "url": "/10006/list_1.json" }, { "id": 10008, "title": "国际", "type": 1, "url": "/10008/list_1.json" }, { "id": 10010, "title": "体育", "type": 1, "url": "/10010/list_1.json" }, { "id": 10091, "title": "生活", "type": 1, "url": "/10091/list_1.json" }, { "id": 10012, "title": "旅游", "type": 1, "url": "/10012/list_1.json" }, { "id": 10095, "title": "科技", "type": 1, "url": "/10095/list_1.json" }, { "id": 10009, "title": "军事", "type": 1, "url": "/10009/list_1.json" }, { "id": 10093, "title": "时尚", "type": 1, "url": "/10093/list_1.json" }, { "id": 10011, "title": "财经", "type": 1, "url": "/10011/list_1.json" }, { "id": 10094, "title": "育儿", "type": 1, "url": "/10094/list_1.json" }, { "id": 10105, "title": "汽车", "type": 1, "url": "/10105/list_1.json" } ], "id": 10000, "title": "新闻", "type": 1 }, { "id": 10002, "title": "专题", "type": 10, "url": "/10006/list_1.json", "url1": "/10007/list1_1.json" }, { "id": 10003, "title": "组图", "type": 2, "url": "/10008/list_1.json" }, { "dayurl": "", "excurl": "", "id": 10004, "title": "互动", "type": 3, "weekurl": "" } ],
        "extend": [ 10007, 10006, 10008, 10014, 10012, 10091, 10009, 10010, 10095 ],
        "retcode": 200 }

![json][json 2]

/** * 网络分类信息的封装 * * 字段名字必须和服务器返回的字段名一致, 方便gson解析 * */
    public class NewsData { 
    
        public int retcode;
        public ArrayList<NewsMenuData> data;
    
        // 侧边栏数据对象
        public class NewsMenuData { 
            public String id;
            public String title;
            public int type;
            public String url;
    
            public ArrayList<NewsTabData> children;
    
            @Override
            public String toString() {
                return "NewsMenuData [title=" + title + ", children=" + children
                        + "]";
            }
        }
    
        // 新闻页面下11个子页签的数据对象
        public class NewsTabData { 
            public String id;
            public String title;
            public int type;
            public String url;
    
            @Override
            public String toString() {
                return "NewsTabData [title=" + title + "]";
            }
        }
    
        @Override
        public String toString() {
            return "NewsData [data=" + data + "]";
        }
    
    }

NewsData mNewsData Gson gson = new Gson();
    mNewsData = gson.fromJson(result, NewsData.class);

解析结果

![gson][]

## **5.1 标准解析** ##

public class GsonTools { 
        public GsonTools() {
        }
    
        public static String createGsonString(Object object) {
            Gson gson = new Gson();
            String gsonString = gson.toJson(object);
            return gsonString;
        }
    
        public static <T> T changeGsonToBean(String gsonString, Class<T> cls) {
            Gson gson = new Gson();
            T t = gson.fromJson(gsonString, cls);
            return t;
        }
    
        public static <T> T changeGsonToBean(String gsonString, Type type) {
            Gson gson = new Gson();
            T t = gson.fromJson(gsonString,type);
            return t;
        }
    
        public static <T> List<T> changeGsonToList(String gsonString, Class<T> cls) {
            Gson gson = new Gson();
            List<T> list = gson.fromJson(gsonString, new TypeToken<List<T>>() {
            }.getType());
            return list;
        }
    
        public static <T> List<Map<String, T>> changeGsonToListMaps(String gsonString) {
            List<Map<String, T>> list = null;
            Gson gson = new Gson();
            list = gson.fromJson(gsonString, new TypeToken<List<Map<String, T>>>(){}.getType());
            return list;
        }
    
        public static <T> Map<String, T> changeGsonToMaps(String gsonString) {
            Map<String, T> map = null;
            Gson gson = new Gson();
            map = gson.fromJson(gsonString, new TypeToken<Map<String, T>>(){}.getType());
            return map;
        }
    }

Json的解析成 java 对象

Gson gson = new Gson();
    
    // 将json 转化成 java 对象
    Student stu = gson.fromJson(json, Student.class);
    
    // 将 json 转化 成 List泛型
    List<Student> stus = gson.fromJson(json, new TypeToken<List<Student>>() {}.getType());
    
    // 将 json 转化 成 Map泛型 
    Map<String,String> map = gson.fromJson(json, new TypeToken<Map<String,String>>() {}.getType());

## **5.2 泛型解析** ##

[
        {
            "des": "2005-2014 你的校园一直在这儿。中国最大的实名制SNS网络平台，大学生",
            "downloadUrl": "app/com.renren.mobile.android/com.renren.mobile.android.apk",
            "iconUrl": "app/com.renren.mobile.android/icon.jpg",
            "id": 1580615,
            "name": "人人",
            "packageName": "com.renren.mobile.android",
            "size": 21803987,
            "stars": 2 },
        {
            "des": "中国电信掌上营业厅是中国电信集团【官方】唯一指定服务全国电信用户的自助服务客户端",
            "downloadUrl": "app/com.ct.client/com.ct.client.apk",
            "iconUrl": "app/com.ct.client/icon.jpg",
            "id": 1540629,
            "name": "掌上营业厅",
            "packageName": "com.ct.client",
            "size": 4794202,
            "stars": 2 }
    ]

![json][json 3]

public class AppInfoBean { 
        public String   des;            // 应用的描述
        public String   downloadUrl;    // 应用的下载地址
        public String   iconUrl;        // 应用的图标地址
        public long     id;             // 应用的id
        public String   name;           // 应用的名字
        public String   packageName;    // 应用的包名
        public long     size;           // 应用的长度
        public float    stars;          // 应用的评分
    }

public List<AppInfoBean> parseJson(String jsonString) {
            Gson gson = new Gson();
    
            /*=============== 泛型解析 ===============*/
            return gson.fromJson(jsonString, new TypeToken<List<AppInfoBean>>() {
            }.getType());
    
        }

Type type = new TypeToken<ArrayList<String>>() {}.getType();

Gson gson = new Gson();
    List<HomeBean> list = gson.fromJson(result,new TypeToken<List< HomeBean>>(){}.getType());

Map<String,String> map = gson.fromJson(response,new TypeToken<Map<String,String>>(){}.getType());

public abstract class BaseProtocol<T> { 
        protected abstract String getInterfaceKey();
        protected T parseJson(String result){
            ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass();
            Type[] types = genericSuperclass.getActualTypeArguments();
            Type type = types[0];
            return new Gson().fromJson(result,type);
        }
    }

## **5.3 节点解析** ##

适合属性比较多的情况，要啥取啥

![jsonelement][]

![json][json 4]

Gson的节点对象

<table> 
 <thead> 
  <tr> 
   <th align="left">节点对象</th> 
   <th align="left">说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left">JsonElement</td> 
   <td align="left">所有的节点都是JsonElement对象</td> 
  </tr> 
  <tr> 
   <td align="left">JsonPrimitive</td> 
   <td align="left">基本的数据类型的节点对象， JsonElement的子类</td> 
  </tr> 
  <tr> 
   <td align="left">JsonNull</td> 
   <td align="left">代表空节点对象，即有key，value为空，JsonElement 的子类</td> 
  </tr> 
  <tr> 
   <td align="left">JsonObject</td> 
   <td align="left">对象 数据类型的节点对象, JsonElement的子类</td> 
  </tr> 
  <tr> 
   <td align="left">JsonArray</td> 
   <td align="left">数组 数据类型的节点对象, JsonElement的子类</td> 
  </tr> 
 </tbody> 
</table>

## **5.4 JsonElement的取值** ##

JsonPrimitive : value 的 取值对应 java

int，double，float，long，short，boolean，char，byte，String，BigDecimal，BigInteger，Number

JsonObject : value 的 取值对应 java 的 Object 对象

JsonArray : value 的 取值对应 java 的 List 及其子类对象

//1、获得 解析者
    
    JsonParser parser = new JsonParser();
    
    //2、获得 根节点元素
    
    JsonElement root = parser.parse(json);
    
    //3、根据 文档判断根节点属于 什么类型的 Gson节点对象
    
    //假如文档 显示 根节点 为对象类型
    // 获得 根节点 的实际 节点类型
    JsonObject element = root.getAsJsonObject();
    
    //4、取得 节点 下 的某个节点的 value
    
    // 获得 name 节点的值，name 节点为基本数据节点
    JsonPrimitive nameJson = element.getAsJsonPrimitive("name");
    String name = nameJson.getAsString();
    
    // 获得 students 节点的值, students 节点为 数组数据节点
    JsonArray arrayJson = element.getAsJsonArray("students");
    // 获得数据 的长度
    int size = arrayJson.size();
    for(int i = 0; i < size; i++) {
        //获得每一个json 元素
        JsonElement e = arrayJson.get(i);
        // 通过元素 得到需要的节点值 TODO:
    }

public List<AppInfoBean> parseJson(String jsonString) {
            Gson gson = new Gson();
            /*=============== 泛型解析 ===============*/
            // return gson.fromJson(jsonString, new TypeToken<List<AppInfoBean>>() { 
            // }.getType());
            /*=============== 结点解析 ===============*/
    
            List<AppInfoBean> appInfoBeans = new ArrayList<AppInfoBean>();
            // 获得json的解析器
            JsonParser parser = new JsonParser();
    
            JsonElement rootJsonElement = parser.parse(jsonString);
    
            // JsonElement-->转换成jsonArray
            JsonArray rootJsonArray = rootJsonElement.getAsJsonArray();
    
            // 遍历jsonArray
            for (JsonElement itemJsonElement : rootJsonArray) {
                // jsonElement-->转换成JsonObject
                JsonObject itemJsonObject = itemJsonElement.getAsJsonObject();
    
                // 得到具体的jsonPrimitivie
                JsonPrimitive desPrimitivie = itemJsonObject.getAsJsonPrimitive("des");
                // jsonPrimitivie-->转换成具体的类型
                String des = desPrimitivie.getAsString();
    
                // 得到具体的jsonPrimitivie
                JsonPrimitive downloadUrlPrimitivie = itemJsonObject.getAsJsonPrimitive("downloadUrl");
                // jsonPrimitivie-->转换成具体的类型
                String downloadUrl = downloadUrlPrimitivie.getAsString();
    
                String iconUrl = itemJsonObject.get("iconUrl").getAsString();
                long id = itemJsonObject.get("id").getAsLong();
                String name = itemJsonObject.get("name").getAsString();
                String packageName = itemJsonObject.get("packageName").getAsString();
                long size = itemJsonObject.get("size").getAsLong();
                float stars = itemJsonObject.get("stars").getAsFloat();
    
                AppInfoBean info = new AppInfoBean();
                info.des = des;
                info.downloadUrl = downloadUrl;
                info.iconUrl = iconUrl;
                info.id = id;
                info.name = name;
                info.packageName = packageName;
                info.size = size;
                info.stars = stars;
                // 添加到集合
                appInfoBeans.add(info);
    
            }
    
            // 返回结果
            return appInfoBeans;
        }

com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON

Gson gson = new Gson();
    JsonReader reader = new JsonReader(new StringReader(result1));
    reader.setLenient(true);
    Userinfo userinfo1 = gson.fromJson(reader, Userinfo.class);

String trimmed = result1.trim();
    gson.fromJson(trimmed, T);

com.google.gson.internal.LinkedTreeMap cannot be cast to com.google.smartcit

public static <T> List<T> changeGsonToList(String gsonString, Class<T> cls) {
            Gson gson = new Gson();
            List<T> list = gson.fromJson(gsonString, new TypeToken<List<T>>() {
            }.getType());
            return list;
        }

public static <T> List<T> getObjectList(String jsonString,Class<T> cls){  
            List<T> list = new ArrayList<T>();  
            try {  
                Gson gson = new Gson();  
                JsonArray arry = new JsonParser().parse(jsonString).getAsJsonArray();  
                for (JsonElement jsonElement : arry) {  
                    list.add(gson.fromJson(jsonElement, cls));  
                }  
            } catch (Exception e) {  
                e.printStackTrace();  
            }  
            return list;  
        }

## 5.5 处理json格式特殊字符 ##

public static String changeStr(String json){
            json = json.replaceAll(",", "，");
            json = json.replaceAll(":", "：");
            json = json.replaceAll("\\[", "【"); 
            json = json.replaceAll("\\]", "】"); 
            json = json.replaceAll("\\{", "<"); 
            json = json.replaceAll("\\}", ">"); 
            json = json.replaceAll("\"", "”"); 
    
            return json.toString();
        }

[Gson]: http://blog.csdn.net/axi295309066/article/details/53339918
[Gson_JSON]: http://blog.csdn.net/axi295309066/article/details/53334086
[Gson_json]: http://blog.csdn.net/axi295309066/article/details/53335014
[Gson 1]: http://www.jianshu.com/p/fc5c9cdf3aab
[Gson 2]: http://www.jianshu.com/p/d62c2be60617
[Link 1]: http://blog.csdn.net/axi295309066/article/details/53349708
[json]: /images/20220714/cf8172685a8540a69ebddd2108c75593.png
[json 1]: /images/20220714/0be2ee8beecf409f83226f3926883250.png
[json 2]: /images/20220714/91d4253dacf841b0900f23d31a438b5b.png
[gson]: /images/20220714/4694eec76aa44ddea83daf5387b91b7d.png
[json 3]: /images/20220714/8cdd84176db2498b8fcd7fefa9b7390b.png
[jsonelement]: /images/20220714/ebcef76ed65548de9051fe2f8cd5e78e.png
[json 4]: /images/20220714/d1b860c286c249cc98eb24f93f32405f.png