parser JSON file JSONARRAY AND JSONOBJECT in java

Question

if my JSON file is like this:

{"result":[{"sentence": "Chinese government cafes people cafe crackdown", "id": 1, "txtfile": "002.txt"}, {"sentence": "kalf alo ldk alf", "id": 2, "txtfile": "003.txt"}]}

How to read .json file into java and parser the JSON to get the sentence, id, txtfile ? since my json consists both JSONARRAY AND JSONOBJECT.

private static String jsonFile="D:\\MYJSON.json";

    public static void main(String[] args){

        JSONParser parser = new JSONParser();

        try{

            Object obj=parser.parse(new FileReader(jsonFile));  
            JSONObject jsonObject = (JSONObject) obj;
            String sentence=(String) jsonObject.get("sentence");
            System.out.println(sentence);
} catch (Exception e){
        e.printStackTrace();
    }
    }
}

I have the error as:java.lang.ClassCastException: java.lang.String cannot be cast to org.json.JSONObject at yyym.ttt.main(ttt.java:46)

This is my JSON

"{\"result\":[{\"sentence\": \"said Chinese government cafes people cafe crackdown\", \"id\": 1, \"txtfile\": \"002.txt\"}, {\"sentence\": \"kalf alo ldk alf\", \"id\": 2, \"txtfile\": \"003.txt\"}]}"

I checked my JSON file is valid. however, When I print it out. It start with " , how to solve the problem?

the output is     "{\"result\":[{\"sentence\": \"said Chinese government cafes people cafe crackdown\", \"id\": 1, \"txtfile\": \"002.txt\"}, {\"sentence\": \"kalf alo ldk alf\", \"id\": 2, \"txtfile\": \"003.txt\"}]}"
org.json.JSONException: A JSONObject text must begin with '{' at 1 [character 2 line 1]
    at org.json.JSONTokener.syntaxError(JSONTokener.java:451)
    at org.json.JSONObject.<init>(JSONObject.java:195)
    at org.json.JSONObject.<init>(JSONObject.java:319)
    at yyym.ttt.main(ttt.java:26)

i think this is what you want : stackoverflow.com/questions/2591098/how-to-parse-json-in-java — Mohsen_Fatemi
– Mohsen_Fatemi, Commented Oct 7, 2016 at 8:50
Post code of JSONParser. Looks like something wrong in your file or your method to parse it — Shaishav Jogani
– Shaishav Jogani, Commented Oct 7, 2016 at 9:16
@HiPownedBi Which jar you are using for json?? and json parser?? — Jay Prakash
– Jay Prakash, Commented Oct 7, 2016 at 10:28

Ravikumar · Accepted Answer · 2016-10-07 09:21:25Z

2

Result is an array, first you have to get that array, loop over that array and then get the desired json objects.

Library used in the following code is - org.json

Code

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class Example {

    public static void main(String[] args) {

        //String jsonString = "{\"result\":[{\"sentence\": \"Chinese government cafes people cafe crackdown\", \"id\": 1, \"txtfile\": \"002.txt\"}, {\"sentence\": \"kalf alo ldk alf\", \"id\": 2, \"txtfile\": \"003.txt\"}]}";

        String jsonString = readJsonFile("filePath");

        try {
            JSONObject jsonObject = new JSONObject(jsonString);
            JSONArray result = jsonObject.getJSONArray("result");
            for (int i =0; i < result.length(); i++){
                JSONObject j = result.getJSONObject(i);
                String s = j.getString("sentence");
                int id = j.getInt("id");
                String txtFile = j.getString("txtfile");
                System.out.println("Sentence is " + s);
                System.out.println("Id is " + id);
                System.out.println("text file is " + txtFile);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    public static String readJsonFile(String filePath) {
    String jsonData = "";
    BufferedReader br = null;
    try {
        String line;
        br = new BufferedReader(new FileReader(filePath));
        while ((line = br.readLine()) != null) {
            jsonData += line + "\n";
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (br != null) {
                br.close();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    return jsonData;
}
}

Output

Sentence is Chinese government cafes people cafe crackdown.
Id is 1
text file is 002.txt
Sentence is kalf alo ldk alf
Id is 2
text file is 003.txt

edited Oct 7, 2016 at 9:21

answered Oct 7, 2016 at 9:07

Ravikumar

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7 Comments

HiPownedBi Over a year ago

Thanks. it works. However, I would like to get the JSON content from my json file. The issue might be dut to " Object obj=parser.parse(new FileReader(jsonFile)); " as I have this error: java.lang.ClassCastException: java.lang.String cannot be cast to org.json.JSONObject at yyym.ttt.main(ttt.java:41) . May I know where I did wrong?

Ravikumar Over a year ago

@HiPownedBi You can read your json text file to get the desired json String. Did you check whether the json text in the file is a valid json?

HiPownedBi Over a year ago

Thanks a lot. I am sorry to bother u again. why I get this error: A JSONObject text must begin with '{' at 1 [character 2 line 1] . I check my JSON content with your //String jsonString = "{\"result\":[{\"sentence\": \"Chinese government cafes people cafe crackdown\", \"id\": 1, \"txtfile\": \"002.txt\"}, {\"sentence\": \"kalf alo ldk alf\", \"id\": 2, \"txtfile\": \"003.txt\"}]}"; They are the same. Why I read the .json file get the above error

Ravikumar Over a year ago

@HiPownedBi In simple terms the error says your json is not valid. Check you json here - Jsonlint

Ravikumar Over a year ago

@HiPownedBi How you are assigning your json to the string? for ex are you doing it like this String json = ""\{\""?

|

Jay Prakash · Accepted Answer · 2016-10-07 10:39:05Z

1

I am using this jars file: jsonsimple.jar

http://www.java2s.com/Code/Jar/j/Downloadjsonsimplejar.htm

 private static String jsonFile="D:\\MYJSON.json";
 public static void main(String[] args) {

        JSONParser parser = new JSONParser();

        try {

            Object obj = parser.parse(new FileReader(jsonFile));
            JSONObject jsonObject = (JSONObject) obj;
            System.out.println("KK:"+jsonObject.toString());
            JSONArray jarray = (JSONArray) jsonObject.get("result");
            for (int i=0;i<jarray.size();i++) {
                jsonObject = (JSONObject) jarray.get(i);
                String sentence = (String)jsonObject.get("sentence"); 
             System.out.println(sentence);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Output:

{"result":[{"sentence":"Chinese government cafes people cafe crackdown","txtfile":"002.txt","id":1},{"sentence":"kalf alo ldk alf","txtfile":"003.txt","id":2}]}
Chinese government cafes people cafe crackdown
kalf alo ldk alf

answered Oct 7, 2016 at 10:39

Jay Prakash

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2 Comments

HiPownedBi Over a year ago

I do not know why i get this error by using your code. java.lang.ClassCastException: java.lang.String cannot be cast to org.json.simple.JSONObject

Jay Prakash Over a year ago

@HiPownedBi use these import : import org.json.simple.JSONArray; import org.json.simple.JSONObject; import org.json.simple.parser.JSONParser;

m.qadhavi · Accepted Answer · 2016-10-07 09:08:28Z

0

result is JsonArray, and you can loop over it to get JsonObjects e.g:

Object obj=parser.parse(new FileReader(jsonFile));  
JSONObject jsonObject = (JSONObject) obj;
JSONArray values = item.json.optJSONArray("result");
JSONObject json;
String sentence = "";
//loop to get object
for (int i = 0; i < values.length(); i++){
    json = values.getJSONObject(i);
    //get sentenence
    sentence = json.getString("sentence");
}

answered Oct 7, 2016 at 9:08

m.qadhavi

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Comments

Rajesh Satvara · Accepted Answer · 2016-10-07 09:09:59Z

0

 String sentence=null;
    JSONArray jsonArray = jsonObject.getJSONArray("result");
    if(jsonArray.length()>0){
     for(int i=0;i<jsonArray.length();i++){
        JSONObject jo=jsonArray.getJSONObject(i);
        sentence=jo.getString("sentence");
       }
   }

edited Oct 7, 2016 at 9:09

Rajesh Satvara

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answered Oct 7, 2016 at 9:02

Musaddique S

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1 Comment

HiPownedBi Over a year ago

I still have this error: java.lang.ClassCastException: java.lang.String cannot be cast to org.json.JSONObject at yyym.ttt.main(ttt.java:41)

sandeepmaaram · Accepted Answer · 2016-10-07 09:20:34Z

Use instanceof to check whether that data is JsonObject or JsonArray

Sample code given below

public void main() {
    String jsonFile = "D:\\MYJSON.json";
    JSONParser parser = new JSONParser();
    try {
        Object obj = parser.parse(new FileReader(jsonFile));
        if (obj instanceof JSONObject) {
            JSONObject jsonObject = (JSONObject) obj;
            String sentence = jsonObject.optString("sentence");
            System.out.println(sentence);
        } else if (obj instanceof JSONArray) {
            JSONArray jsonArray = (JSONArray) obj;
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObj = jsonArray.getJSONObject(i);
                String sentence = jsonObj.optString("sentence");
                System.out.println(sentence);
            }//end of for loop
        }//end of else if
    } catch (Exception e) {
        e.printStackTrace();
    }
}

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