Android Gson深入分析

目前解析json有三种工具：org.json（Java常用的解析），fastjson（阿里巴巴工程师开发的），Gson（Google官网出的），解析速度最快的是Gson，下载地址：https://code.google.com/p/google-gson/

什么是JSON:

JSON即JavaScript Object Natation, 它是一种轻量级的数据交换格式, 与XML一样, 是广泛被采用的客户端和服务端交互的解决方案.

JSON对象: 

JSON中对象(Object)以"{"开始, 以"}"结束. 对象中的每一个item都是一个key-value对, 表现为"key:value"的形式, key-value对之间使用逗号分隔. 如:{"name":"coolxing", "age"=24, "male":true, "address":{"street":"huiLongGuan", "city":"beijing", "country":"china"}}. JSON对象的key只能是string类型的, 而value可以是string, number, false, true, null, Object对象甚至是array数组, 也就是说可以存在嵌套的情况.

JSON数组: 

JSON数组(array)以"["开始, 以"]"结束, 数组中的每一个元素可以是string, number, false, true, null, Object对象甚至是array数组, 数组间的元素使用逗号分隔. 如["coolxing", 24, {"street":"huiLongGuan", "city":"beijing", "country":"china"}].

Gson的基本使用方法：

通过获取JsonReader对象解析JSON数据：

String jsonData = "[{\"username\":\"arthinking\",\"userId\":001},{\"username\":\"Jason\",\"userId\":002}]";try{JsonReader reader = new JsonReader(new StringReader(jsonData));reader.beginArray();while(reader.hasNext()){reader.beginObject();while(reader.hasNext()){String tagName = reader.nextName();if(tagName.equals("username")){System.out.println(reader.nextString());}else if(tagName.equals("userId")){System.out.println(reader.nextString());}}reader.endObject();}reader.endArray();}catch(Exception e){e.printStackTrace();}

通过把JSON数据映射成一个对象，使用Gson对象的fromJson()方法获取一个对象数组进行操作：

创建JSON数据对应的一个POJO对象User.java：

public class User {private String username ;private int userId ;public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public int getUserId() {return userId;}public void setUserId(int userId) {this.userId = userId;}}

使用Gson对象获取User对象数据进行相应的操作：

Type listType = new TypeToken<LinkedList<User>>(){}.getType();Gson gson = new Gson();LinkedList<User> users = gson.fromJson(jsonData, listType);for (Iterator iterator = users.iterator(); iterator.hasNext();) {User user = (User) iterator.next();System.out.println(user.getUsername());System.out.println(user.getUserId());}

如果要处理的JSON字符串只包含一个JSON对象，则可以直接使用fromJson获取一个User对象：

String jsonData = "{\"username\":\"arthinking\",\"userId\":001}";Gson gson = new Gson();User user = gson.fromJson(jsonData, User.class);System.out.println(user.getUsername());System.out.println(user.getUserId());

解析复杂实例：

数据格式：

{    "data": {        "partnerteamlist": [            {                "pteamId": 72825,                "ptitle": "随摄影/共6套服装/准爸准妈共拍/免费肚画/底片全送。",                "pteamprice": 288            },            {                "pteamId": 72598,                "ptitle": "随摄影/拍摄200张/4本相册/品质拍摄/送全新婚纱。",                "pteamprice": 2888            },            {                "pteamId": 72613,                "ptitle": "随摄影/送全新婚纱/多外景拍摄/服装不限数量/绝无二次消费！",                "pteamprice": 3699            },            {                "pteamId": 72638,                "ptitle": "随摄影/服装不限数量/高品质拍摄260张/送全新婚纱。",                "pteamprice": 4299            },            {                "pteamId": 72716,                "ptitle": "随摄影/3组服装造型/内外景拍摄/完全透明消费！",                "pteamprice": 388            }        ],        "liketeamlist": [            {                "lteamId": 65886,                "ltitle": "爱丽尔婚纱摄影/2本相册/6套服装造型/拍摄不限最低拍摄150张。",                "limage": "http://img.pztuan.com/upfile/team/2013/0712/201307120257551465.jpg",                "lteamprice": 518,                "lmarketprice": 3999            },            {                "lteamId": 57133,                "ltitle": "陶冶摄影/婚纱闺蜜/6组服装造型/拍摄不低于120张！",                "limage": "http://img.pztuan.com/upfile/team/2013/0628/201306281115249737.jpg",                "lteamprice": 580,                "lmarketprice": 3380            }        ],        "feedbacks": {            "feedbacklist": [                {                    "comment": "5分",                    "createtime": "2014.07.08 13:38",                    "score": 5,                    "username": "l***2"                }            ],            "totalcount": 1,            "totalscore": 5        }    },    "err": null,    "state": 1}

实体类（里面的成员变量和接口的返回值名称一 一对应才能保证解析正确）：

package com.pztuan.entity;import java.util.List;public class OtherDetail {private int state;private List<err> err;private OtherDetail2 data;public int getState() {return state;}public void setState(int state) {this.state = state;}public List<err> getErr() {return err;}public void setErr(List<err> err) {this.err = err;}public OtherDetail2 getData() {return data;}public void setData(OtherDetail2 data) {this.data = data;}public class OtherDetail2 {private List<partnerteamlist> partnerteamlist;private List<liketeamlist> liketeamlist;private List<feedbacks> feedbacks;public List<liketeamlist> getLiketeamlist() {return liketeamlist;}public void setLiketeamlist(List<liketeamlist> liketeamlist) {this.liketeamlist = liketeamlist;}public List<feedbacks> getFeedbacks() {return feedbacks;}public void setFeedbacks(List<feedbacks> feedbacks) {this.feedbacks = feedbacks;}public class partnerteamlist {private int pteamId;private String ptitle;private Double pteamprice;public int getPteamId() {return pteamId;}public void setPteamId(int pteamId) {this.pteamId = pteamId;}public String getPtitle() {return ptitle;}public void setPtitle(String ptitle) {this.ptitle = ptitle;}public Double getPteamprice() {return pteamprice;}public void setPteamprice(Double pteamprice) {this.pteamprice = pteamprice;}}public class liketeamlist {private int lteamId;private String ltitle;private String limage;private Double lteamprice;private Double lmarketprice;public int getLteamId() {return lteamId;}public void setLteamId(int lteamId) {this.lteamId = lteamId;}public String getLtitle() {return ltitle;}public void setLtitle(String ltitle) {this.ltitle = ltitle;}public String getLimage() {return limage;}public void setLimage(String limage) {this.limage = limage;}public Double getLteamprice() {return lteamprice;}public void setLteamprice(Double lteamprice) {this.lteamprice = lteamprice;}public Double getLmarketprice() {return lmarketprice;}public void setLmarketprice(Double lmarketprice) {this.lmarketprice = lmarketprice;}}public class feedbacks {private int totalcount;private Double totalscore;private List<feedbacklist> feedbacklist;public int getTotalcount() {return totalcount;}public void setTotalcount(int totalcount) {this.totalcount = totalcount;}public Double getTotalscore() {return totalscore;}public void setTotalscore(Double totalscore) {this.totalscore = totalscore;}public List<feedbacklist> getFeedbacklist() {return feedbacklist;}public void setFeedbacklist(List<feedbacklist> feedbacklist) {this.feedbacklist = feedbacklist;}public class feedbacklist {private String username;private String comment;private String createtime;private Double score;public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getComment() {return comment;}public void setComment(String comment) {this.comment = comment;}public String getCreatetime() {return createtime;}public void setCreatetime(String createtime) {this.createtime = createtime;}public Double getScore() {return score;}public void setScore(Double score) {this.score = score;}}}public List<partnerteamlist> getPartnerteamlist() {return partnerteamlist;}public void setPartnerteamlist(List<partnerteamlist> partnerteamlist) {this.partnerteamlist = partnerteamlist;}}public class err {private int code;private String msg;public int getCode() {return code;}public void setCode(int code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}}}

注意上面内部类的运用。

解析：

Gson gson = new Gson();OtherDetail d = gson.fromJson(jsonString,Detail.class);//取值的时候就从父类一层一层调子类成员（重要）

若出现引用异常，请查看Java内部类设计原则。

如有问题请留言，转载注明出处。

参考：http://www.itzhai.com/android-to-parse-json-data-using-gson.html

           http://blog.csdn.net/caijunjun1006/article/details/11762841