我有一个非常简单的JSON,其中包含对产品的评论,例如:
{
"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."
}
我想用GSON将它读入我的Java应用程序。我已经建立了一个班级来保存每篇评论的结果:
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...
要阅读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
使用此代码,我只能检索JSON中的第一个评论,所以我的问题是:如何遍历所有读者并获得下一个评论?我不需要将评论存储在List中,只需要访问该对象一次。任何帮助都超过欢迎。
答案 0 :(得分:68)
你必须获取列表中的整个数据,然后进行迭代,因为它是一个文件,否则会变得效率低下。
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
答案 1 :(得分:21)
只需解析为数组:
Review[] reviews = new Gson().fromJson(jsonString, Review[].class);
然后,如果您需要,您也可以这样创建一个列表:
List<Review> asList = Arrays.asList(reviews);
P.S。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"
},
[...]
]
答案 2 :(得分:1)
万一您需要从文件进行解析,我找到了一个最佳解决方案,可以在Java代码中使用HashMap<String, String>
来更好地操作它。
尝试以下代码:
public HashMap<String, String> myMethodName() throws FileNotFoundException
{
String path = "absolute path to your file";
BufferedReader bufferedReader = new BufferedReader(new FileReader(path));
Gson gson = new Gson();
HashMap<String, String> json = gson.fromJson(bufferedReader, HashMap.class);
return json;
}