Android Gson深入分析

眼下解析json有三种工具：org.json（Java经常使用的解析），fastjson（阿里巴巴project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, 是广泛被採用的client和服务端交互的解决方式.

JSON对象: 

JSON中对象(Object)以"{"開始, 以"}"结束. 对象中的每个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仅仅能是string类型的, 而value能够是string, number, false, true, null, Object对象甚至是array数组, 也就是说能够存在嵌套的情况.

JSON数组: 

JSON数组(array)以"["開始, 以"]"结束, 数组中的每个元素能够是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的基本用法：

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数据相应的一个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());
}

假设要处理的JSON字符串仅仅包括一个JSON对象。则能够直接使用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本相冊/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/全然透明消费！
",
                "pteamprice": 388
            }
        ],
        "liketeamlist": [
            {
                "lteamId": 65886,
                "ltitle": "爱丽尔婚纱摄影/2本相冊/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 一相应才干保证解析正确）：

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。

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

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