为什么不读取 JSON 文件？

Question

这段代码应该读取 JSON 文件，这是一个元素数组，然后它应该读取该数组的所有元素，但我只得到一行结果，它看起来像这样：

reviews[{"sourceId":"890cdd7974cdf8aabe6e9051f5a87303bdb933ae","logoHref":null,"reviewerId":null,"reviewCreatedOnTime":161157...

读取文件的代码如下：

FileReader read=new FileReader("C:\Users\User\eclipse-workspace\Task\files\reviews.json");
    JSONParser parser=new JSONParser();
    Object obj=parser.parse(read);
    JSONObject jsonObject=new JSONObject();
    jsonObject=(JSONObject) obj;
    
    JSONArray reviews = new JSONArray();
    reviews=(JSONArray) jsonObject.get("reviews");
    
    Iterator<Map.Entry> itr1 = jsonObject.entrySet().iterator();
    while (itr1.hasNext()) {
        Map.Entry pair = itr1.next();
        System.out.println(pair.getKey() + " " + pair.getValue());
    }
//json file
{
"reviews":[
  {
    "id": 2097047,
    "reviewId": "93f131be27dc1122bb7ef0048ad10e4f",
    "reviewFullText": "5 star review",
    "reviewText": "5 star review",
    "numLikes": 0,
    "numComments": 0,
    "numShares": 0,
    "rating": 5,
    "reviewCreatedOn": "2 months ago",
    "reviewCreatedOnDate": "2021-01-25T13:00:35+00:00",
    "reviewCreatedOnTime": 1611579635,
    "reviewerId": null,
    "reviewerUrl": null,
    "reviewerName": "Reviewer #20",
    "reviewerEmail": null,
    "sourceType": "custom",
    "isVerified": false,
    "source": "custom",
    "sourceName": "1-20 Reviews",
    "sourceId": "890cdd7974cdf8aabe6e9051f5a87303bdb933ae",
    "tags": [],
    "href": null,
    "logoHref": null,
    "photos": []
  },

Answer 1

你的第一个问题是你没有使用 reviews 对象，而是仍然引用主要的 json 对象。

Iterator<Map.Entry> itr1 = jsonObject.entrySet().iterator();

应该将 jsonObject 更改为 reviews，但同时给出它是 JSONArray 的事实，因为您说过它只会是数组，你可以只从数组中取出第一个元素，即 .get(0)

那么您的代码将更改如下：

Iterator<Entry> itr1 = ((JSONObject)reviews.get(0)).entrySet().iterator();
while (itr1.hasNext()) {
  Map.Entry pair = itr1.next();
  System.out.println(pair.getKey() + " " + pair.getValue());
}

并且您的输出符合您的预期：

sourceId 890cdd7974cdf8aabe6e9051f5a87303bdb933ae
logoHref null
reviewerId null
reviewCreatedOnTime 1611579635
isVerified false
rating 5
reviewerUrl null
reviewFullText 5 star review
source custom
numLikes 0
reviewCreatedOnDate 2021-01-25T13:00:35+00:00
photos []
tags []
numComments 0
reviewerName Reviewer #20
sourceType custom
reviewerEmail null
numShares 0
id 2097047
sourceName 1-20 Reviews
href null
reviewId 93f131be27dc1122bb7ef0048ad10e4f
reviewCreatedOn 2 months ago
reviewText 5 star review

如果你想处理所有条评论，并将每条评论当成一张地图来阅读，你可以如下操作：

    FileReader read = new FileReader(
        "C:\Users\User\eclipse-workspace\Task\files\reviews.json");
    JSONParser parser = new JSONParser();
    Object obj = parser.parse(read);
    JSONObject jsonObject = new JSONObject();
    jsonObject = (JSONObject) obj;

    JSONArray reviews = new JSONArray();
    reviews = (JSONArray) jsonObject.get("reviews");

    Iterator<Entry> itr1 = reviews.iterator();
    while (itr1.hasNext()) {

      Iterator<Entry> itr2 = ((JSONObject) itr1.next()).entrySet().iterator();
      while (itr2.hasNext()) {
        Map.Entry pair = itr2.next();
        System.out.println(pair.getKey() + " " + pair.getValue());
      }
    }

旁注：我鼓励您使用更简单的方法来构建良好的库，例如 jackson 或 gson 而不是以这种方式操作数据。

为什么不读取 JSON 文件？

Why does not read JSON file?

java

json

dictionary

iterator

filereader