GSON 详解

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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>(){}.getType();
Gson gson = new Gson();
LinkedList 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;
    private OtherDetail2 data;

    public int getState() {
        return state;
    }

    public void setState(int state) {
        this.state = state;
    }

    public List getErr() {
        return err;
    }

    public void setErr(List err) {
        this.err = err;
    }

    public OtherDetail2 getData() {
        return data;
    }

    public void setData(OtherDetail2 data) {
        this.data = data;
    }

    public class OtherDetail2 {
        private List partnerteamlist;
        private List liketeamlist;
        private List feedbacks;

        public List getLiketeamlist() {
            return liketeamlist;
        }

        public void setLiketeamlist(List liketeamlist) {
            this.liketeamlist = liketeamlist;
        }

        public List getFeedbacks() {
            return feedbacks;
        }

        public void setFeedbacks(List 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;

            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 getFeedbacklist() {
                return feedbacklist;
            }

            public void setFeedbacklist(List 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 getPartnerteamlist() {
            return partnerteamlist;
        }

        public void setPartnerteamlist(List 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。