JSON初體驗(一)
在學校的呆了一段時間，馬上又要回去工作了，不說了，我現在介紹一下json相關的內容
1.JSON數據格式(總的來說，json就是一個字符串)
1.整體結構
String json1 = "{"id":12,"name":"Tom"}";
String json2 = "[{"id":12,"name":"Tom"},{"id":12,"name":"Tom"}]";
2.json對象
a.json對象的結構:{key1:value1,key2:value2,key3:value3}
b.key的數據類型:字符串
c.value的數據類型:
1.數值
2.字符串
3.null
4.json數組[]
5.json對象{}
d.例子
正確的:{“name”:"TOM","age":12}
錯誤的:{"aa":"a",3}
3.json數組
a.json數組的結構:[value1,value2,value3]
b.value的數據類型:
1.數值
2.字符串
3.null
4.json數組[]
5.json對象{}
c.例子
正確的:[1,"ab",[],{"n":132,“b”:"abc"}]
錯誤的:[1,"a":3]
2.JSON解析方向
1.將java對象(包含集合)轉換為json格式字符串(在服務器端應用)
2.將json格式字符串轉換為java對象,包含集合(在客戶端應用)
3.json和java之間的轉換關系
a.json對應java對象
b.json數組與java對象構成的list相對應
3.JSON解析技術
1.Android原生技術:
特點:編程相對麻煩
數據之間轉換(demo):
a.將json格式的字符串{}轉換為java對象
API：
JSONObject(String json):將json字符串解析為json對象
Xxx getXxx(String name):根據name,在json對象中得到對應的Value
Xxx optXxx(String name):根據name,在json對象中得到對應的value
註意:
optXxx方法會在對應的key中的值不存在的時候返回一個空字符串或者返回
你指定的默認值，但是getString方法會出現空指針異常的錯誤
String json = "{\n" +
" \"id\":2,\n" +
" \"name\":\"Tom\",\n" +
" \"price\":12.3,\n" +
" \"imagePath\":\"http://www.baidu.com\"\n" +
"}"
JSONObject jsonObject = new JSONObject(json);
int id = jsonObject.optInt("id");
String name = jsonObject.optString("name");
double price = jsonObject.optDouble("price");
String imagePath = jsonObject.optString("imagePath");
b.將json格式的字符串[]轉換為java對象的List
API:
JSONArray(String json):將json字符串解析為json數組
int length():得到json數組中元素的個數
Xxx getXxx(int index):根據下標得到json數組中對應的元素數據
Xxx optXxx(int index):根據下標得到json數組中對應的元素數據
註意:
optXxx方法會在對應的key中的值不存在的時候返回一個空字符串或者返回
你指定的默認值，但是getString方法會出現空指針異常的錯誤
String json = "[\n" +
" {\n" +
" \"id\":1,\n" +
" \"imagePath\":\"www.baidu.com\",\n" +
" \"name\":\"Tom1\",\n" +
" \"price\":12.3\n" +
" },\n" +
" {\n" +
" \"id\":1,\n" +
" \"imagePath\":\"www.douban.com\",\n" +
" \"name\":\"Tom2\",\n" +
" \"price\":12.5\n" +
" }\n" +
"]";
List<First> list = new ArrayList<First>();
JSONArray jsonArray = new JSONArray(json);
for (int i = 0; i < jsonArray.length() ; i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
if(jsonObject != null){
int id = jsonObject.optInt("id");
String imagePath = jsonObject.optString("imagePath");
String name = jsonObject.optString("name");
Double price = jsonObject.optDouble("price");
First first = new First(id, name, price, imagePath);
list.add(first);
}
}
for (int i = 0; i <list.size() ; i++) {
System.out.println(list.get(i).toString());
}
c.復雜json數據解析
String json = "{\n" +
" \"data\":{\n" +
" \"count\":5,\n" +
" \"items\":[\n" +
" {\n" +
" \"id\":45,\n" +
" \"title\":\"堅果\"\n" +
" },\n" +
" {\n" +
" \"id\":132,\n" +
" \"title\":\"炒貨\"\n" +
" },\n" +
" {\n" +
" \"id\":166,\n" +
" \"title\":\"蜜餞\"\n" +
" },\n" +
" {\n" +
" \"id\":195,\n" +
" \"title\":\"果脯\"\n" +
" },\n" +
" {\n" +
" \"id\":196,\n" +
" \"title\":\"禮盒\"\n" +
" }\n" +
" ]\n" +
" },\n" +
" \"rs_code\":\"1000\",\n" +
" \"rs_msq\":\"success\"\n" +
"}";
List<Second> list = new ArrayList<Second>();
JSONObject jsonObject = new JSONObject(json);
JSONObject data = jsonObject.optJSONObject("data");
String rs_code = jsonObject.optString("rs_code");
String rs_msq = jsonObject.optString("rs_msq");
int count = data.optInt("count");
JSONArray items = data.optJSONArray("items");
for (int i = 0; i < items.length(); i++) {
JSONObject jj = items.getJSONObject(i);
int id = jj.optInt("id");
String title = jj.optString("title");
Second second = new Second(id,title);
list.add(second);
}
d.特殊json數據解析
FilmInfo類
public class FilmInfo { private int code; private List<FilmBean> list; public int getCode() { return code; } public void setCode(int code) { this.code = code; } public List<FilmBean> getList() { return list; } public void setList(List<FilmBean> list) { this.list = list; } public static class FilmBean{ private String aid; private String author; private int coins; private String copyright; private String create; public String getAid() { return aid; } public void setAid(String aid) { this.aid = aid; } public String getAuthor() { return author; } public void setAuthor(String author) { this.author = author; } public int getCoins() { return coins; } public void setCoins(int coins) { this.coins = coins; } public String getCopyright() { return copyright; } public void setCopyright(String copyright) { this.copyright = copyright; } public String getCreate() { return create; } public void setCreate(String create) { this.create = create; } @Override public String toString() { return "FilmBean{" + "aid=‘" + aid + ‘\‘‘ + ", author=‘" + author + ‘\‘‘ + ", coins=" + coins + ", copyright=‘" + copyright + ‘\‘‘ + ", create=‘" + create + ‘\‘‘ + ‘}‘; }
} @Override public String toString() { return "FilmInfo{" + "code=" + code + ", list=" + list + ‘}‘; } }
此時對json進行分析
String json = "{\n" +
" \"code\":0,\n" +
" \"list\":{\n" +
" \"0\":{\n" +
" \"aid\":\"6008965\",\n" +
" \"author\":\"嗶哩嗶哩番劇\",\n" +
" \"coins\":170,\n" +
" \"copyright\":\"Copy\",\n" +
" \"create\":\"2016-08-25 21:34\"\n" +
" },\n" +
" \"1\":{\n" +
" \"aid\":\"6008938\",\n" +
" \"author\":\"嗶哩嗶哩番劇\",\n" +
" \"coins\":404,\n" +r
" \"copyright\":\"Copy\",\n" +
" \"create\":\"2016-08-25 21:33\"\n" +
" }\n" +
" }\n" +
"}";
FilmInfo filmInfo = new FilmInfo();
JSONObject jsonObject = new JSONObject(json);
int code = jsonObject.optInt("code");
filmInfo.setCode(code);
List<FilmInfo.FilmBean> filmList = new ArrayList<FilmInfo.FilmBean>();
filmInfo.setList(filmList);
JSONObject list = jsonObject.optJSONObject("list");
for (int i = 0; i <list.length() ; i++) {
JSONObject jsonObject1 = list.optJSONObject(i + "");
String aid = jsonObject1.optString("aid");
String author = jsonObject1.optString("author");
int coins = jsonObject1.optInt("coins");
String copyright = jsonObject1.optString("copyright");
String create = jsonObject1.optString("create");
FilmInfo.FilmBean filmBean = new FilmInfo.FilmBean();
filmBean.setAid(aid);
filmBean.setAuthor(author);
filmBean.setCoins(coins);
filmBean.setCopyright(copyright);
filmBean.setCreate(create);
filmList.add(filmBean);
}
System.out.println(filmInfo);
最後在補充一點，這裏面的org.json.jsonObject的maven為
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20140107</version>
</dependency>
JSON初體驗(一)