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。