Java 从嵌套的 JSON 对象中检索值
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Retrieving values from nested JSON Object
提问by m.aibin
I've got JSON file, which I want to parse. The JSON file ("myfile") has format as follows:
我有要解析的 JSON 文件。JSON 文件（“myfile”）的格式如下：
{
"LanguageLevels": {
"1": "Pocz?tkuj?cy",
"2": "?rednioZaawansowany",
"3": "Zaawansowany",
"4": "Ekspert"
}
}
I want to retrieve value (?rednioZaawansowany) of Key 2 from Language Levels.
我想从语言级别检索密钥 2 的值 (?rednioZaawansowany)。
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
public class JsonSimpleExample {
public static void main(String[] args) {
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(new FileReader("myfile");
JSONObject jsonObject = (JSONObject) obj;
JSONObject jsonChildObject = (JSONObject)jsonObject.get("LanguageLevels");
What to do next? How I can iterate over it?
接下来做什么？我如何迭代它？
采纳答案by Xiao Liang
Maybe you're not using the latest version of a JSON for Java Library.
也许您没有使用最新版本的 JSON for Java 库。
json-simplehas not been updated for a long time, while JSON-Javawas updated 2 month ago.
json-simple好久没更新了，JSON-Java2个月前就更新了。
JSON-Javacan be found on GitHub, here is the link to its repo: https://github.com/douglascrockford/JSON-java
JSON-Java可以在 GitHub 上找到，这里是它的 repo 的链接：https: //github.com/douglascrockford/JSON-java
After switching the library, you can refer to my sample code down below:
切换库后，您可以参考我下面的示例代码：
public static void main(String[] args) {
String JSON = "{\"LanguageLevels\":{\"1\":\"Pocz\u0105tkuj\u0105cy\",\"2\":\"\u015arednioZaawansowany\",\"3\":\"Zaawansowany\",\"4\":\"Ekspert\"}}\n";
JSONObject jsonObject = new JSONObject(JSON);
JSONObject getSth = jsonObject.getJSONObject("LanguageLevels");
Object level = getSth.get("2");
System.out.println(level);
}
And as JSON-Javaopen-sourced, you can read the code and its document, they will guide you through.
作为JSON-Java开源，您可以阅读代码及其文档，他们将指导您完成。
Hope that it helps.
希望它有帮助。
回答by dehlen
JSONArray jsonChildArray = (JSONArray) jsonChildArray.get("LanguageLevels");
JSONObject secObject = (JSONObject) jsonChildArray.get(1);
I think this should work, but i do not have the possibility to test it at the moment..
我认为这应该有效，但我目前无法对其进行测试..
回答by Jakub Kotowski
You can see that JSONObjectextends a HashMap, so you can simply use it as a HashMap:
您可以看到JSONObject扩展了 a HashMap，因此您可以简单地将其用作 HashMap：
JSONObject jsonChildObject = (JSONObject)jsonObject.get("LanguageLevels");
for (Map.Entry in jsonChildOBject.entrySet()) {
System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}
回答by eabyshev
To see all keys of Jsonobject use this
要查看 Jsonobject 的所有键，请使用它
String JSON = "{\"LanguageLevels\":{\"1\":\"Pocz\u0105tkuj\u0105cy\",\"2\":\"\u015arednioZaawansowany\",\"3\":\"Zaawansowany\",\"4\":\"Ekspert\"}}\n";
JSONObject obj = new JSONObject(JSON);
Iterator iterator = obj.keys();
String key = null;
while (iterator.hasNext()) {
key = (String) iterator.next();
System.out.pritnln(key);
}
回答by preetesh gurjar
You will have to iterate step by step into nested JSON.
您必须逐步迭代到嵌套的 JSON 中。
for e.g a JSON received from Google geocoding api
例如从 Google 地理编码 api 收到的 JSON
{
"results" : [
{
"address_components" : [
{
"long_name" : "Bhopal",
"short_name" : "Bhopal",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Bhopal",
"short_name" : "Bhopal",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Madhya Pradesh",
"short_name" : "MP",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "India",
"short_name" : "IN",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "Bhopal, Madhya Pradesh, India",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 23.3326697,
"lng" : 77.5748062
},
"southwest" : {
"lat" : 23.0661497,
"lng" : 77.2369767
}
},
"location" : {
"lat" : 23.2599333,
"lng" : 77.412615
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 23.3326697,
"lng" : 77.5748062
},
"southwest" : {
"lat" : 23.0661497,
"lng" : 77.2369767
}
}
},
"place_id" : "ChIJvY_Wj49CfDkR-NRy1RZXFQI",
"types" : [ "locality", "political" ]
}
],
"status" : "OK"
}
I shall iterate in below given fashionto "location" : { "lat" : 23.2599333, "lng" : 77.412615
我将以下面给定的方式迭代到 "location" : { "lat" : 23.2599333, "lng" : 77.412615
//recieve JSON in json object
//在json对象中接收JSON
JSONObject json = new JSONObject(output.toString());
JSONArray result = json.getJSONArray("results");
JSONObject result1 = result.getJSONObject(0);
JSONObject geometry = result1.getJSONObject("geometry");
JSONObject locat = geometry.getJSONObject("location");
//"iterate onto level of location";
double lat = locat.getDouble("lat");
double lng = locat.getDouble("lng");
