如何在Java中读取JSON？

Question

I have a JSON String and I got the data element's data to JSONObject . After I read this that resultant string is as follows. I'm using org.json library.

String dataStr = "[{\"name\":\"jhonny\",\"counts\":[\"50\",\"44\",\"46\"],\"url\":\"google\"},
 {\"name\":\"john\",\"counts\":[\"344\",\"4\",\"18\"],\"url\":\"yahoo\"}]";

I tried to read the each element like following,

String dataStr = report.get("data").toString();
JSONObject data = new JSONObject(dataStr.substring(1));
System.out.println(data);

But my output is,

{"name":"jhonny","counts":["50","44","46"],"url":"google"}

The output contains only one element. How can I fix this?

Answer 1

Using the org.json library:

JSONObject obj = new JSONObject("{interests : [{interestKey:Dogs}, {interestKey:Cats}]}");

List<String> list = new ArrayList<String>();
JSONArray array = obj.getJSONArray("interests");
for(int i = 0 ; i < array.length() ; i++){
    list.add(array.getJSONObject(i).getString("interestKey"));
}

Answer 2

JSONArray jsonarray = new JSONArray(datastr);
for(int i=0; i<jsonarray.length(); i++){
    JSONObject data= jsonarray.getJSONObject(i);

    System.out.println(data);
}   

Answer 3

The problem is you are trying to read JSONArray as JSONObject.

To parse JSONArray you need to do something like: (Not sure which library you are using)

for (int i = 0; i < jsonarray.length(); i++) {
    JSONObject jsonobject = jsonarray.getJSONObject(i);
    // jsonobject holds the desired element.
}

Answer 4

If you analyze your json string, you will notice that your json string contains multiple json object without outer object like :-

{ 
"outer":{
          {\"name\":\"jhonny\",\"counts\":[\"50\",\"44\",\"46\"],\"url\":\"google\"},
          {\"name\":\"jhonny\",\"counts\":[\"50\",\"44\",\"46\"],\"url\":\"google\"}
        }
}

The way you are parsing require this kind of json structure. Your json string is actually just a jsonarray. So do like this way :

JSONArray jsonarray = new JSONArray(datastr);
for(int i=0; i<jsonarray.length(); i++){
    JSONObject data= jsonarray.getJSONObject(i);
}

For more you can visit this link that gives you good explanation to how to read json in java