尝试获取 Json 中某个元素内的元素或其本身的值返回 null

发布于 2024-10-07 10:27:59 字数 1553 浏览 2 评论 0原文

您好，我正在尝试从 JsonObject 获取元素的值。我正在使用java Gson 库。

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"));

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"
        }
      }

当我获取顶部元素“路由”时，它很好并打印它显示元素内部的内容，但是当我尝试获取元素“摘要”时如图所示，返回为空，这就是输出中显示的内容，因此随后我无法获取它的值。怎么了？如何获取任意 JsonElement 的值？请尽快回复我。提前致谢。

原文

Hello Im trying to get the value of an element from a JsonObject. i'm using java with the
Gson library.

here is the related part of the code:

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:

"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.

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佞臣 2024-10-14 10:27:59

路由是一个 JavaScript 数组。 Summary 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"); 或等效方法。我没有使用过您的 Java 库，但 JS 代码将是 jsonObject.routes[0].summary

编辑：查找 GSON 文档和更新的代码。

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