JSON初体验
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在学校的呆了一段时间，马上又要回去工作了，不说了，我现在介绍一下json相关的内容
1.JSON数据格式(总的来说，json就是一个字符串)
1.整体结构
String json1 = "{"id":12,"name":"Tom"}";
String json2 = "[{"id":12,"name":"Tom"},{"id":12,"name":"Tom"}]";
2.json对象
a.json对象的结构:{key1:value1,key2:value2,key3:value3}
b.key的数据类型:字符串
c.value的数据类型:
1.数值
2.字符串
3.null
4.json数组[]
5.json对象{}
d.例子
正确的:{“name”:"TOM","age":12}
错误的:{"aa":"a",3}
3.json数组
a.json数组的结构:[value1,value2,value3]
b.value的数据类型:
1.数值
2.字符串
3.null
4.json数组[]
5.json对象{}
c.例子
正确的:[1,"ab",[],{"n":132,“b”:"abc"}]
错误的:[1,"a":3]
2.JSON解析方向
1.将java对象(包含集合)转换为json格式字符串(在服务器端应用)
2.将json格式字符串转换为java对象,包含集合(在客户端应用)
3.json和java之间的转换关系
a.json对应java对象
b.json数组与java对象构成的list相对应
3.JSON解析技术
1.android原生技术:
特点:编程相对麻烦
数据之间转换(demo):
a.将json格式的字符串{}转换为java对象
API：
JSONObject(String json):将json字符串解析为json对象
Xxx getXxx(String name):根据name,在json对象中得到对应的Value
Xxx optXxx(String name):根据name,在json对象中得到对应的value
注意:
optXxx方法会在对应的key中的值不存在的时候返回一个空字符串或者返回
你指定的默认值，但是getString方法会出现空指针异常的错误
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.将json格式的字符串[]转换为java对象的List
API:
JSONArray(String json):将json字符串解析为json数组
int length():得到json数组中元素的个数
Xxx getXxx(int index):根据下标得到json数组中对应的元素数据
Xxx optXxx(int index):根据下标得到json数组中对应的元素数据
注意:
optXxx方法会在对应的key中的值不存在的时候返回一个空字符串或者返回
你指定的默认值，但是getString方法会出现空指针异常的错误
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.复杂json数据解析
String json = "{\n" +
" \"data\":{\n" +
" \"count\":5,\n" +
" \"items\":[\n" +
" {\n" +
" \"id\":45,\n" +
" \"title\":\"坚果\"\n" +
" },\n" +
" {\n" +
" \"id\":132,\n" +
" \"title\":\"炒货\"\n" +
" },\n" +
" {\n" +
" \"id\":166,\n" +
" \"title\":\"蜜饯\"\n" +
" },\n" +
" {\n" +
" \"id\":195,\n" +
" \"title\":\"果脯\"\n" +
" },\n" +
" {\n" +
" \"id\":196,\n" +
" \"title\":\"礼盒\"\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数据解析
FilmInfo类
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 + ‘}‘; } }
此时对json进行分析
String json = "{\n" +
" \"code\":0,\n" +
" \"list\":{\n" +
" \"0\":{\n" +
" \"aid\":\"6008965\",\n" +
" \"author\":\"哔哩哔哩番剧\",\n" +
" \"coins\":170,\n" +
" \"copyright\":\"Copy\",\n" +
" \"create\":\"2016-08-25 21:34\"\n" +
" },\n" +
" \"1\":{\n" +
" \"aid\":\"6008938\",\n" +
" \"author\":\"哔哩哔哩番剧\",\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);
最后在补充一点，这里面的org.json.jsonObject的maven为
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20140107</version>
</dependency>
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