GSON是Google提供的用來在Java對象和JSON資料之間進行映射的Java類庫。可以将一個Json字元轉成一個Java對象，或者将一個Java轉化為Json字元串。
特點:
a、快速、高效
b、代碼量少、簡潔
c、面向對象
d、資料傳遞和解析友善
Gon介紹
com.google.code.gson
gson
2.8.0
Gson的建立方式
Gson gson = new gson();
通過GsonBuilder()，可以配置多種配置。
Gson gson = new GsonBuilder()
.setLenient()// json寬松
.enableComplexMapKeySerialization()//支援Map的key為複雜對象的形式
.serializeNulls() //智能null
.setPrettyPrinting()// 調教格式
.disableHtmlEscaping() //預設是GSON把HTML 轉義的
.create();
Gson的基本用法
之前寫過一個擷取天氣參數的API,就需要去解析傳回的json資料，就以此為例。
擷取天氣參數
String url = "http://t.weather.sojson.com/api/weather/city/101010100";
String resultStr = HttpClientUtil.sendGetRequest(url, "UTF-8");
傳回結果(就不格式化了)
{shidu=15%, pm25=15.0, pm10=35.0, quality=優, wendu=3, ganmao=各類人群可自由活動,
yesterday={date=06, sunrise=07:36, high=高溫 3.0℃, low=低溫 -7.0℃, sunset=17:03,
aqi=58.0, ymd=2019-01-06, week=星期日, fx=西南風, fl=<3級, type=晴,
notice=願你擁有比陽光明媚的心情}, forecast=[{date=07, sunrise=07:36, high=高溫 2.0℃,
low=低溫 -7.0℃, sunset=17:04, aqi=48.0, ymd=2019-01-07, week=星期一, fx=北風,
fl=3-4級, type=多雲, notice=陰晴之間，謹防紫外線侵擾}, {date=08, sunrise=07:36,
high=高溫 1.0℃, low=低溫 -9.0℃, sunset=17:05, aqi=28.0, ymd=2019-01-08, week=星期二,
fx=北風, fl=3-4級, type=晴, notice=願你擁有比陽光明媚的心情}, {date=09, sunrise=07:36,
high=高溫 2.0℃, low=低溫 -8.0℃, sunset=17:06, aqi=83.0, ymd=2019-01-09, week=星期三,
fx=西南風, fl=<3級, type=多雲, notice=陰晴之間，謹防紫外線侵擾}, {date=10, sunrise=07:36,
high=高溫 4.0℃, low=低溫 -7.0℃, sunset=17:07, aqi=128.0, ymd=2019-01-10, week=星期四,
fx=西南風, fl=<3級, type=晴, notice=願你擁有比陽光明媚的心情}, {date=11, sunrise=07:36,
high=高溫 5.0℃, low=低溫 -6.0℃, sunset=17:08, aqi=238.0, ymd=2019-01-11, week=星期五,
fx=西南風, fl=<3級, type=多雲, notice=陰晴之間，謹防紫外線侵擾}]}
可以建立一個天氣的Bean，将傳回的json資料轉換成對象
//GSON直接解析成對象
ResultBean resultBean = new Gson().fromJson(resultStr,ResultBean.class);
解析簡單的json
data:{
shidu = 15 % ,
pm25 = 15.0,
pm10 = 35.0,
quality = 優,
wendu = 3,
ganmao = 各類人群可自由活動,
}
JsonObject jsonObject =(JsonObject) new JsonParser().parse(resultStr);
Int wendu = jsonObject.get("data").getAsJsonObject().get("wendu").getAsInt();
String quality= jsonObject.get("data").getAsJsonObject().get("quality").getAsString();
解析多層對象
data:{
shidu = 15 % ,
pm25 = 15.0,
pm10 = 35.0,
quality = 優,
wendu = 3,
ganmao = 各類人群可自由活動,
yesterday :{
date = 06,
sunrise = 07: 36,
high = 高溫 3.0℃,
low = 低溫 - 7.0℃,
sunset = 17: 03,
aqi = 58.0,
ymd = 2019 - 01 - 06,
week = 星期日,
fx = 西南風,
fl = < 3 級,
type = 晴,
notice = 願你擁有比陽光明媚的心情
}
}
JsonObject jsonObject = (JsonObject) new JsonParser().parse(resultStr);
JsonObject yesterday = jsonObject.get("data").getAsJsonObject().get("yesterday ").getAsJsonObject();
String type = yesterday.get("type").getAsString();
解析帶數組的json
{
shidu = 15 % , pm25 = 15.0, pm10 = 35.0, quality = 優, wendu = 3, ganmao = 各類人群可自由活動,
yesterday = {
date = 06,
sunrise = 07: 36,
high = 高溫 3.0℃,
low = 低溫 - 7.0℃,
sunset = 17: 03,
aqi = 58.0,
ymd = 2019 - 01 - 06,
week = 星期日,
fx = 西南風,
fl = < 3 級,
type = 晴,
notice = 願你擁有比陽光明媚的心情
},
forecast = [{
date = 07,
sunrise = 07: 36,
high = 高溫 2.0℃,
low = 低溫 - 7.0℃,
sunset = 17: 04,
aqi = 48.0,
ymd = 2019 - 01 - 07,
week = 星期一,
fx = 北風,
fl = 3 - 4 級,
type = 多雲,
notice = 陰晴之間， 謹防紫外線侵擾
}, {
date = 08,
sunrise = 07: 36,
high = 高溫 1.0℃,
low = 低溫 - 9.0℃,
sunset = 17: 05,
aqi = 28.0,
ymd = 2019 - 01 - 08,
week = 星期二,
fx = 北風,
fl = 3 - 4 級,
type = 晴,
notice = 願你擁有比陽光明媚的心情
}, {
date = 09,
sunrise = 07: 36,
high = 高溫 2.0℃,
low = 低溫 - 8.0℃,
sunset = 17: 06,
aqi = 83.0,
ymd = 2019 - 01 - 09,
week = 星期三,
fx = 西南風,
fl = < 3 級,
type = 多雲,
notice = 陰晴之間， 謹防紫外線侵擾
}, {
date = 10,
sunrise = 07: 36,
high = 高溫 4.0℃,
low = 低溫 - 7.0℃,
sunset = 17: 07,
aqi = 128.0,
ymd = 2019 - 01 - 10,
week = 星期四,
fx = 西南風,
fl = < 3 級,
type = 晴,
notice = 願你擁有比陽光明媚的心情
}, {
date = 11,
sunrise = 07: 36,
high = 高溫 5.0℃,
low = 低溫 - 6.0℃,
sunset = 17: 08,
aqi = 238.0,
ymd = 2019 - 01 - 11,
week = 星期五,
fx = 西南風,
fl = < 3 級,
type = 多雲,
notice = 陰晴之間， 謹防紫外線侵擾
}]
}
JsonObject jsonObject =(JsonObject) new JsonParser().parse(resultStr);
//擷取data
JsonObject data = jsonObject.get("data").getAsJsonObject();
//擷取數組
JsonArray forecast = data.getAsJsonObject().get("forecast").getAsJsonArray();
String type = forecast.get(0).getAsJsonObject().get("type").getAsString();