Android 使用Gson解析json案例詳解

阿新 • • 發佈：2019-01-03

一、目前解析json有三種工具：org.json（Java常用的解析），fastjson（阿里巴巴工程師開發的），Gson（Google官網出的），解析速度最快的是Gson，下載地址：https://code.google.com/p/google-gson/

二、什麼是JSON:

JSON即JavaScript Object Natation, 它是一種輕量級的資料交換格式, 與XML一樣, 是廣泛被採用的客戶端和服務端互動的解決方案.

三、JSON物件:

JSON中物件(Object)以”{“開始, 以”}”結束. 物件中的每一個item都是一個key-value對, 表現為”key:value”的形式, key-value對之間使用逗號分隔. 如:{“name”:”coolxing”, “age”=24, “male”:true, “address”:{“street”:”huiLongGuan”, “city”:”beijing”, “country”:”china”}}. JSON物件的key只能是string型別的, 而value可以是string, number, false, true, null, Object物件甚至是array陣列, 也就是說可以存在巢狀的情況.

四、JSON陣列:

JSON陣列(array)以”[“開始, 以”]”結束, 陣列中的每一個元素可以是string, number, false, true, null, Object物件甚至是array陣列, 陣列間的元素使用逗號分隔. 如[“coolxing”, 24, {“street”:”huiLongGuan”, “city”:”beijing”, “country”:”china”}].

五、Gson的基本使用方法：
通過獲取JsonReader物件解析JSON資料：

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();
}

通過把JSON資料對映成一個物件，使用Gson物件的fromJson()方法獲取一個物件陣列進行操作：
建立JSON資料對應的一個POJO物件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物件獲取User物件資料進行相應的操作：

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());
}

如果要處理的JSON字串只包含一個JSON物件，則可以直接使用fromJson獲取一個User物件：

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());

解析複雜例項：

資料格式：（對於格式比較亂json資料，我們可以使用HIJSON工具進行程式碼的格式化！）

{
    "data": {
        "partnerteamlist": [
            {
                "pteamId": 72825,
                "ptitle": "隨攝影/共6套服裝/準爸準媽共拍/免費肚畫/底片全送。",
                "pteamprice": 288
            },
            {
                "pteamId": 72598,
                "ptitle": "隨攝影/拍攝200張/4本相簿/品質拍攝/送全新婚紗。",
                "pteamprice": 2888
            },
            {
                "pteamId": 72613,
                "ptitle": "隨攝影/送全新婚紗/多外景拍攝/服裝不限數量/絕無二次消費！",
                "pteamprice": 3699
            },
            {
                "pteamId": 72638,
                "ptitle": "隨攝影/服裝不限數量/高品質拍攝260張/送全新婚紗。",
                "pteamprice": 4299
            },
            {
                "pteamId": 72716,
                "ptitle": "隨攝影/3組服裝造型/內外景拍攝/完全透明消費！",
                "pteamprice": 388
            }
        ],
        "liketeamlist": [
            {
                "lteamId": 65886,
                "ltitle": "愛麗爾婚紗攝影/2本相簿/6套服裝造型/拍攝不限最低拍攝150張。",
                "limage": "http://img.pztuan.com/upfile/team/2013/0712/201307120257551465.jpg",
                "lteamprice": 518,
                "lmarketprice": 3999
            },
            {
                "lteamId": 57133,
                "ltitle": "陶冶攝影/婚紗閨蜜/6組服裝造型/拍攝不低於120張！",
                "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
}

實體類（裡面的成員變數和介面的返回值名稱一一對應才能保證解析正確）：

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;
        }
    }
}

注意上面內部類的運用。
解析：

Gson gson = new Gson();
OtherDetail d = gson.fromJson(jsonString,Detail.class);//取值的時候就從父類一層一層調子類成員（重要）

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