1.背景
最近在解析json的數據，發現直接用HQL邏輯很繁瑣，於是藉助java，再添加爲UDF。
2.什麼是json(參考：http://www.json.org/)
json一共有兩種數據結構
(1)以(key/value)對形式存在的無序的jsonObject對象，其以"{"(左括號)開始，以"}"(右括號)結束。
格式如下：
{
"名稱1":"值1",
"名稱2":"值2",
"名稱3":"值3"
}名稱和值之間用":"(冒號)對應，不同名稱/值之間使用","(逗號)分隔。下面舉一個簡單的例子。
{
"name":"xiaoming",
"age":10,
"sex":"male"
}這就是一個最簡單的json對象，對於這種數據格式，key必須是string，value可以是string,number,object,array,true,false,null等等數據類型。
(2)有序的value集合，這種形式被稱爲jsonArray，數組是值(value)的有序集合。一個數組以“[”（左中括號）開始，“]”（右中括號）結束。值之間使用“,”（逗號）分隔。
{
"employee":[
{"name":"John","age":20,"sex":"男"},
{"name":"Anna","age":25,"sex":"男"},
{"name":"Peter","age":22,"sex":"男"}
]
}在上面的例子中，對象employee是包含三個對象的數組。每個對象包含某個員工的信息(姓名，年齡，性別)。
3.舉例
在這裏我們可以學到的是：
(1)區別JSONObject與JSONArray
(2)能夠解析json數據
下面是一個json文件：
{
"resultcode": "200",
"reason": "successed!",
"result": {
"sk": {
"temp": "24",
"wind_direction": "西南風",
"wind_strength": "2級",
"humidity": "51%",
"time": "10:11"
},
"today": {
"temperature": "16℃~27℃",
"weather": "陰轉多雲",
"weather_id": {
"fa": "02",
"fb": "01"
},
"wind": "西南風3-4 級",
"week": "星期四",
"city": "濱州",
"date_y": "2015年06月04日",
"dressing_index": "舒適",
"dressing_advice": "建議着長袖T恤、襯衫加單褲等服裝。年老體弱者宜着針織長袖襯衫、馬甲和長褲。",
"uv_index": "最弱",
"comfort_index": "",
"wash_index": "較適宜",
"travel_index": "",
"exercise_index": "較適宜",
"drying_index": ""
},
"future": [
{
"temperature": "16℃~27℃",
"weather": "陰轉多雲",
"weather_id": {
"fa": "02",
"fb": "01"
},
"wind": "西南風3-4 級",
"week": "星期四",
"date": "20150604"
},
{
"temperature": "20℃~32℃",
"weather": "多雲轉晴",
"weather_id": {
"fa": "01",
"fb": "00"
},
"wind": "西風3-4 級",
"week": "星期五",
"date": "20150605"
},
{
"temperature": "23℃~35℃",
"weather": "多雲轉陰",
"weather_id": {
"fa": "01",
"fb": "02"
},
"wind": "西南風3-4 級",
"week": "星期六",
"date": "20150606"
},
{
"temperature": "20℃~33℃",
"weather": "多雲",
"weather_id": {
"fa": "01",
"fb": "01"
},
"wind": "北風微風",
"week": "星期日",
"date": "20150607"
},
{
"temperature": "22℃~34℃",
"weather": "多雲",
"weather_id": {
"fa": "01",
"fb": "01"
},
"wind": "西南風3-4 級",
"week": "星期一",
"date": "20150608"
},
{
"temperature": "22℃~33℃",
"weather": "陰",
"weather_id": {
"fa": "02",
"fb": "02"
},
"wind": "西南風3-4 級",
"week": "星期二",
"date": "20150609"
},
{
"temperature": "22℃~33℃",
"weather": "多雲",
"weather_id": {
"fa": "01",
"fb": "01"
},
"wind": "南風3-4 級",
"week": "星期三",
"date": "20150610"
}
]
},
"error_code": 0
}我們進行解析：package com.exercise;
import java.io.FileNotFoundException;
import java.io.FileReader;
import com.google.gson.JsonArray;
import com.google.gson.JsonIOException;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonSyntaxException;
public class Analyse_json {
public static void main(String args[]) {
String Path = "E:/WorkSpaces/test.json";
JsonParser parser = new JsonParser();// 創建json解析器
try {
// 創建JsonObject對象
JsonObject object = (JsonObject) parser.parse(new FileReader(Path));
// 將json數據轉爲int型的數據
System.out.println("resultcode:" + object.get("resultcode").getAsInt());
// 將json數據轉爲String型的數據
System.out.println("reason:" + object.get("reason").getAsString());
JsonObject result = object.get("result").getAsJsonObject();
JsonObject today = result.get("today").getAsJsonObject();
System.out.println("\n今天的天氣情況");
System.out.println("temperature:" + today.get("temperature").getAsString());
System.out.println("weather:" + today.get("weather").getAsString());
// 得到爲json的數組
JsonArray array = result.get("future").getAsJsonArray();
System.out.println("\n未來幾天的天氣情況");
for (int i = 0; i < array.size(); i++) {
System.out.println("-----------------------");
JsonObject subObject = array.get(i).getAsJsonObject();
System.out.println("temperature:" + subObject.get("temperature").getAsString());
System.out.println("weather:" + subObject.get("weather").getAsString());
System.out.println("wind:" + subObject.get("wind").getAsString());
System.out.println("date:" + subObject.get("date").getAsString());
}
} catch (JsonIOException e) {
e.printStackTrace();
} catch (JsonSyntaxException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}resultcode:200
reason:successed!
今天的天氣情況
temperature:16℃~27℃
weather:陰轉多雲
未來幾天的天氣情況
-----------------------
temperature:16℃~27℃
weather:陰轉多雲
wind:西南風3-4 級
date:20150604
-----------------------
temperature:20℃~32℃
weather:多雲轉晴
wind:西風3-4 級
date:20150605
-----------------------
temperature:23℃~35℃
weather:多雲轉陰
wind:西南風3-4 級
date:20150606
-----------------------
temperature:20℃~33℃
weather:多雲
wind:北風微風
date:20150607
-----------------------
temperature:22℃~34℃
weather:多雲
wind:西南風3-4 級
date:20150608
-----------------------
temperature:22℃~33℃
weather:陰
wind:西南風3-4 級
date:20150609
-----------------------
temperature:22℃~33℃
weather:多雲
wind:南風3-4 級
date:20150610
我們對上面進行解釋：
1.首先創建JsonObject對象object，相對其來講resultcode,reason,result,error_code是並列的。這是很明顯的
JsonObject
2.對於result對象來說，sk,today,future是並列的。這是很明顯的JsonObject
3.剖析future來講，這是一個JSONArray,如果想要解析裏面的信息，需要先get json數組。通過
JsonArray array = result.get("future").getAsJsonArray();實現
分析：
我們通過Gson進行解析，所以在使用前導入Gson.jar
(pom如下：
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.7</version>
</dependency>
)
解析json數據時，
1.需要進行創建Gson解析器
2.創建JsonObject對象
3.將json數據轉爲相應的數據
4.參考
博客
http://www.cnblogs.com/boy1025/p/4551593.html
http://www.cnblogs.com/xiaoluo501395377/p/3446605.html