Gson解析Json数据

 json解析我们不陌生了，不过每次编写解析的代码时总是很头疼，一堆很无聊的代码，如果有50个接口那就得写50个相似的解析处理。其实谷歌和阿里很早就推出了解析json的工具包，谷歌的Gson,阿里的FastJson，还有一个jackJson。有人说jackJson解析速度快，大数据时FastJson要比Gson效率高，小数据时反之。不过我还是偏爱谷歌的Gson，即使效率可能偏低，但是稳定性肯定没得说，FastJson和jackJson就不知道了。

     现在我们来看看Json是如何解析的：

1.下载Gson开发包，放入工程libs目录下：

http://download.csdn.net/detail/itachi85/8617065

2.编写Bean文件：

先看一下json数据：

 {
     "array": [
         {
             "username": "在中",
             "recommend": 0,
             "user_photo": "0",
             "like": false,
             "reply_cnt": 3,
             "distance": "2154m",
             "add_date": "3天前",
             "text": "肯德基快吃吐了，明天去麦当劳看看",
             "stamp__name": null,
             "place_id": 1,
             "ptype": "d",
             "like_cnt": "2",
             "posting_image_url": "1",
             "stamp_name": null,
             "user": 0,
             "stamp__id": null,
             "dislike": "0",
             "icon": "cate_icon_a_09",
             "id": 0,
             "mayor_cnt": 2,
             "place_name": "东大桥肯德基",
         "place_level": 2
         },
         {
             "username": "在中",
             "recommend": 0,
             "user_photo": "0",
             "like": false,
               "reply_cnt": 0,
             "distance": "2425m",
             "add_date": "3天前",
             "text": "这是在跳僵尸舞呢吗？",
             "stamp__name": null,
             "place_id": 7,
             "ptype": "d",
             "like_cnt": "0",
             "posting_image_url": "0",
             "stamp_name": null,
             "user": 0,
             "stamp__id": null,
             "dislike": "0",
             "icon": "cate_icon_b_05",
             "id": 4,
             "mayor_cnt": 2,
             "place_name": "悠唐",
         "place_level": 1
         }
     ],
     "error": 0,
     "next": true
 }

        

紧接着，我们创建bean文件

需要注意的是：

   1、内部嵌套的类必须是static修饰的；
   2、类里面的属性名必须跟Json字段里面的Key是一样的；

NearDynamic.java:

 public class NearDynamic {
     private Boolean next=false;
     private  int error;
     private ArrayList<Dynamic> array = new ArrayList<Dynamic>();
     public Boolean getNext() {
         return next;
     }
     public void setNext(Boolean next) {
         this.next = next;
     }
     public int getError() {
         return error;
     }
     public void setError(int error) {
         this.error = error;
     }
     public ArrayList<DynamicJ> getArray() {
         return array;
     }
     public void setArray(ArrayList<DynamicJ> array) {
         this.array = array;
     }
 }

上面包含了error，next字段，以及包含类型是Dynamic的List,接着我们创建Dynamic：

 public class Dynamic {
     private String username;
     private int recommend;
     private String user_photo;
     private Boolean like;
     private int replycnt;
     private String distance;
     private String add_date;
     private String text;
     private String stamp__name;
     private int place_id;
     private int like_cnt;
     private String ptype;
     private String posting_image_url;
     private String stamp_name;
     private int user;
     private String stamp__id;
     private int dislike=0;
     private String icon;
     private int id;
     private String place_name;
     private int place_level;
     private String mayor_cnt;
     public String getStamp__name() {
         return stamp__name;
     }
     public void setStamp__name(String stamp__name) {
         this.stamp__name = stamp__name;
     }
     public int getLike_cnt() {
         return like_cnt;
     }
     public void setLike_cnt(int like_cnt) {
         this.like_cnt = like_cnt;
     }
     public String getStamp_name() {
         return stamp_name;
     }
     public void setStamp_name(String stamp_name) {
         this.stamp_name = stamp_name;
     }
     public String getStamp__id() {
         return stamp__id;
     }
     public void setStamp__id(String stamp__id) {
         this.stamp__id = stamp__id;
     }
     public int getDislike() {
         return dislike;
     }
     public void setDislike(int dislike) {
         this.dislike = dislike;
     }
     public String getMayor_cnt() {
         return mayor_cnt;
     }
     public void setMayor_cnt(String mayor_cnt) {
         this.mayor_cnt = mayor_cnt;
     }
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public int getUser() {
         return user;
     }
     public void setUser(int user) {
         this.user = user;
     }
     public String getUsername() {
         return username;
     }
     ...
 }

3.使用Gson解析数据：

 private int parseUserData() {
      String strContent = Utils.getJson("neardynamic.txt");
     if (!TextUtils.isEmpty(strContent)) {
         try {
             Gson mgson = new Gson();
             NearDynamic mNearDynamic = mgson.fromJson(
                     strContent, NearDynamic.class);
             ArrayList<Dynamic> mNearDynamicList = mNearDynamic
                     .getArray();
             LogController.i(mNearDynamicList.get(1).getUsername());
             return BaseEngine.RESULT_OK;
         } catch (Exception e) {
             e.printStackTrace();
             return BaseEngine.PARSEJSON_ERR;
         }
     }
     return BaseEngine.RESULT_ERR;
 }

上面代码是一个解析的方法：直接从txt文件中读取数据由Json解析，首先由Json生成NearDynamic,然后得到array中的列表数据，我们取第二个数据打下log，得出的结果是"在中",解析完毕。

如果想要快速测试的话，就写一个txt文件，里面写有json数据，放入assets文件中，然后用下面的方法读取txt文件中数据，再按照上面所讲的就可以了：

 public static String getJson(String filename) {
     InputStream mInputStream = null;
     String resultString = "";
     try {
         mInputStream = App.mContext.getAssets().open(filename);
         byte[] buffer = new byte[mInputStream.available()];
         mInputStream.read(buffer);
         resultString = new String(buffer, "GB2312");
     } catch (IOException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     } finally {
         try {
             mInputStream.close();
         } catch (IOException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
     }
     return resultString.toString();
 }

想要了解Gson更多的方法可以下载http://download.csdn.net/detail/itachi85/8617065中的文件，里面有Gson的文档。