java 从 JSON 获取子数组
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Get sub-array from JSON
提问by user2579475
I parsing some data from a json file. Here is my JSON File.
我从 json 文件中解析了一些数据。这是我的 JSON 文件。
[
{
"topic": "Example1",
"contact": [
{
"ref": [
1
],
"corresponding": true,
"name": "XYZ"
},
{
"ref": [
1
],
"name": "ZXY"
},
{
"ref": [
1
],
"name": "ABC"
},
{
"ref": [
1,
2
],
"name":"BCA"
}
] ,
"type": "Presentation"
},
{
"topic": "Example2",
"contact": [
{
"ref": [
1
],
"corresponding": true,
"name": "XYZ"
},
{
"ref": [
1
],
"name": "ZXY"
},
{
"ref": [
1
],
"name": "ABC"
},
{
"ref": [
1,
2
],
"name":"BCA"
}
] ,
"type": "Poster"
}
]
I can fetch and store data one by one. Like this one
我可以一一获取和存储数据。像这个
JSONArray getContactsArray = new JSONArray(jsonObject.getString("contact"));
for(int a =0 ; a < getContactsArray.length(); a++)
{
JSONObject getJSonObj = (JSONObject)getContactsArray.get(a);
String Name = getJSonObj.getString("name");
}
1)Now, my question is there any way to get all namevalues for each array with single query.
2) Can I get all those values in an Array?
1）现在，我的问题是有什么方法可以name通过单个查询获取每个数组的所有值。2）我可以在一个中获得所有这些值Array吗？
Please correct me, if I am doing anything wrong. Thank you.
请纠正我，如果我做错了什么。谢谢你。
回答by Ravi Thapliyal
Iteration cannot be avoided here as org.jsonand other Json parsers as well provide random access to objects but not to their properties collectively (as a collection). So, you can't query something like "all name properties of all contact objects"unless you probably get a Json parser like Gsonto unmarshall it that way.
此处无法避免迭代，因为org.json其他 Json 解析器也提供对对象的随机访问，但不提供对它们的共同属性（作为集合）的随机访问。因此，您不能查询诸如“所有联系人对象的所有名称属性”之类的内容，除非您可能获得像Gson这样的 Json 解析器以这种方式对其进行解组。
But, that's too much to just avoid a forloop when you can definitely shorten the parse by making use of the appropriate API methods to avoid unnecessary object casts.
但是，for当您可以通过使用适当的 API 方法来避免不必要的对象转换来缩短解析时，仅仅避免循环就太过分了。
JSONArray contacts = jsonObject.getJSONArray("contact");
String[] contactNames = new String[contacts.length()];
for(int i = 0 ; i < contactNames.length; i++) {
contactNames[i] = contacts.getJSONObject(i).getString("name");
}
回答by Juned Ahsan
回答by Tanu Garg
Try this:
试试这个：
Create JSONObject of your file and try to get array of all names and iterate it to get all values.
创建文件的 JSONObject 并尝试获取所有名称的数组并对其进行迭代以获取所有值。
public static String[] getNames(JSONObject jo) {
int length = jo.length();
if (length == 0) {
return null;
}
Iterator i = jo.keys();
String[] names = new String[length];
int j = 0;
while (i.hasNext()) {
names[j] = (String) i.next();
j += 1;
}
return names;
}
