如何使用GSON解析JSON文件

I have a very simple JSON with reviews for products, like:

我有一个非常简单的JSON，包含对产品的评论，比如:

{
  "reviewerID": "A2XVJBSRI3SWDI", 
  "asin": "0000031887", 
  "reviewerName": "abigail", 
  "helpful": [0, 0], 
  "unixReviewTime": 1383523200, 
  "reviewText": "Perfect red tutu for the price. ", 
  "overall": 5.0, 
  "reviewTime": "11 4, 2013", "summary": "Nice tutu"
}
{ 
  "reviewerID": "A2G0LNLN79Q6HR", 
  "asin": "0000031887", 
  "reviewerName": "aj_18 \"Aj_18\"", 
  "helpful": [1, 1], 
  "unixReviewTime": 1337990400, 
  "reviewText": "This was a really cute", 
 "overall": 4.0, 
 "reviewTime": "05 26, 2012", 
 "summary": "Really Cute but rather short."
}

I'd like to read it into my Java app using GSON. I have built a class to hold results for each review:

我想用GSON把它读到我的Java应用中。我建立了一个类来保存每个评审的结果:

public class Review {
    private String reviewerID;
    private String asin;
    private String reviewerName;
    private ArrayList<Integer> helpful;
    private String reviewText;
    private Double overall;
    private String summary;
    private Long unixReviewTime;
    private String reviewTime;

    public Review() {
        this.helpful = Lists.newArrayList();
    }
    // some getters and setters...

To read the JSON file, my code is:

要读取JSON文件，我的代码是:

Gson gson = new Gson();
JsonReader reader = new JsonReader(new FileReader(filename));
Review data = gson.fromJson(reader, Review.class);
data.toScreen(); // prints to screen some values

With this code, I can only retrieve the first review in the JSON, so my question is: how to iterate through all the reader and get the next reviews? I don't need to store the reviews in a List, just need to access the object once. Any help more than welcome.

使用这些代码，我只能检索JSON中的第一个评论，所以我的问题是:如何遍历所有的读者并获得下一个评论?我不需要将评论存储在列表中，只需访问对象一次。任何帮助都是值得欢迎的。

2 个解决方案

#1

You have to fetch the whole data in the list and then do the iteration as it is a file and will become inefficient otherwise.

您必须在列表中获取整个数据，然后进行迭代，因为它是一个文件，否则将变得低效。

private static final Type REVIEW_TYPE = new TypeToken<List<Review>>() {
}.getType();
Gson gson = new Gson();
JsonReader reader = new JsonReader(new FileReader(filename));
List<Review> data = gson.fromJson(reader, REVIEW_TYPE); // contains the whole reviews list
data.toScreen(); // prints to screen some values

#2

just parse as an array:

只是作为数组解析:

Review[] reviews = new Gson().fromJson(jsonString, Review[].class);

then if you need you can also create a list in this way:

如果你需要，你也可以这样创建一个列表:

List<Review> asList = Arrays.asList(reviews);

P.S. your json string should be look like this:

你的json字符串应该是这样的:

[
    {
        "reviewerID": "A2SUAM1J3GNN3B1",
        "asin": "0000013714",
        "reviewerName": "J. McDonald",
        "helpful": [2, 3],
        "reviewText": "I bought this for my husband who plays the piano.",
        "overall": 5.0,
        "summary": "Heavenly Highway Hymns",
        "unixReviewTime": 1252800000,
        "reviewTime": "09 13, 2009"
    },
    {
        "reviewerID": "A2SUAM1J3GNN3B2",
        "asin": "0000013714",
        "reviewerName": "J. McDonald",
        "helpful": [2, 3],
        "reviewText": "I bought this for my husband who plays the piano.",
        "overall": 5.0,
        "summary": "Heavenly Highway Hymns",
        "unixReviewTime": 1252800000,
        "reviewTime": "09 13, 2009"
    },

    [...]
]

#1