java 尝试在 Json 中的某个元素中获取元素或自身的值返回 null
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Trying to get the value of an element or itself inside some element in Json returns null
提问by Muaz
Hello Im trying to get the value of an element from a JsonObject. i'm using java with the Gson library.
您好，我正在尝试从 JsonObject 中获取元素的值。我在 Gson 库中使用 java。
here is the related part of the code:
这是代码的相关部分：
String s = "http://maps.googleapis.com/maps/api/directions/json?origin=30.065634,31.209473&destination=29.984177,31.440052&sensor=false";
URL url = new URL(s);
BufferedReader r = new BufferedReader(new InputStreamReader(
((HttpURLConnection) url.openConnection()).getInputStream()));
JsonStreamParser jsp = new JsonStreamParser(r);
JsonParser jp = new JsonParser();
JsonElement jsonElement = jp.parse(r);
JsonObject jsonObject = jsonElement.getAsJsonObject();
System.out.println(jsonObject.get("summary"));
here is a part of the Json:
这是 Json 的一部分：
"status": "OK", "routes": [ {
"summary": "Mehwar Al Moneeb",
"legs": [ {
"steps": [ {
"travel_mode": "DRIVING",
"start_location": {
"lat": 30.0655100,
"lng": 31.2096600
},
"end_location": {
"lat": 30.0654400,
"lng": 31.2096000
},
"polyline": {
"points": "mdovDksn}DLJ",
"levels": "BB"
},
"duration": {
"value": 1,
"text": "1 min"
},
"html_instructions": "Head \u003cb\u003esouthwest\u003c/b\u003e on \u003cb\u003eOmar Toson\u003c/b\u003e toward \u003cb\u003eMohammed Roshdi\u003c/b\u003e",
"distance": {
"value": 9,
"text": "9 m"
}
}
When I get the top element "routes" its fine and printing it displays what inside the element but when I try to for example to get the element "summary" as shown, the return is null, thats whats is displayed in the output, so subsequently I cannot get the value of it. Whats wrong? how can get the value of any JsonElement? Please reply back to me as soon as you can. Thanks in advance.
当我得到顶部元素“路由”它很好并打印它显示元素内部的内容但是当我尝试例如获取元素“摘要”时，返回为空，这就是输出中显示的内容，所以随后我无法获得它的价值。怎么了？如何获取任何 JsonElement 的值？请尽快回复我。提前致谢。
采纳答案by Shane Daniel
Routes is a javascript array. Summary is a property of the first object in that array, so you need to use jsonObject.getAsJsonArray("routes").get(0).get("summary");or equivalent. I haven't worked with your Java library, but the JS code would be jsonObject.routes[0].summary
Routes 是一个 javascript 数组。摘要是该数组中第一个对象的属性，因此您需要使用jsonObject.getAsJsonArray("routes").get(0).get("summary");或等效。我没有使用过你的 Java 库，但 JS 代码是jsonObject.routes[0].summary
Edit: Looked up GSON Documentationand updated code.
编辑：查找GSON 文档和更新的代码。
