CODEWITHSUNDEEP
javajsonparsing
Piyush
Piyush

Reputation: 388

Reading Multiple JSONObjects from a file

I am storing an arraylist of Objects in JSON format in a file. As soon as new arraylist appears it converts the object in JSON format and append it in the file.The encoding works fine. But while decoding it throws exception. I am quite new in this field and learning.Any help is welcome.

Encoding Code

public static void jsondumpfile(ArrayList<HtmlElementObject> sanitizelog)
{
    try {
        File file = new File("c:\\temp\\auditinfojson.json");

        if(!file.exists()){

            file.createNewFile();
        }


        FileWriter fileWriter = new FileWriter(file,true);
        BufferedWriter bw = new BufferedWriter(fileWriter);
        Gson gson=new Gson();
        //bw.append("---------------");
            //bw.append(gson.toJson(sanitizelog));
        //fw.append(gson.toJson(sanitizelog));
        for(HtmlElementObject eachobj : sanitizelog)

        {

             bw.write(gson.toJson(eachobj));

         }



        //bw.flush();
        bw.close();
    logElementData.clear();


    } catch (IOException e) {
        // TODO: handle exception
        e.printStackTrace();
    }



}

RESULTANT FILE AFTER ENCODING {"appLoginId":1058,"tabId":"1","elementType":"Image","label":"No Image Name","value":"https://admin.xyz.com","seqTrail":"No possible trail sequence","timeStamp":"2014-01-31 13:02:42.618"} {"appLoginId":1058,"tabId":"1","elementType":"Image","label":"No Image Name","value":"https://admin.xyz.com/xyz/images/btn-cancel.gif","seqTrail":"No possible trail sequence","timeStamp":"2014-01-31 13:02:42.625"}

Like this multiple objects are stored.

DECODING/PARSING BACk CODE

public static void extractfromjson() throws IOException
 {



   ArrayList<HtmlElementObject> tCollection = new ArrayList<HtmlElementObject>();
   Gson gson = new Gson();
   BufferedReader bufferedReader = new BufferedReader(new FileReader(
           "c:\\temp\\auditinfojson.json"));
   Type type = new TypeToken<ArrayList<HtmlElementObject>>(){}.getType();
   ArrayList<HtmlElementObject> J_tweet = (ArrayList<HtmlElementObject>)gson.fromJson(bufferedReader, type);
   System.out.println(J_tweet);

    }

EXCEPTION THROWN **com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2** This comes when i want to retrieve the data.

Upvotes: 0

Views: 488

Answers (1)

All Pereira
All Pereira

Reputation: 149

When we have a JSON, the GSON fails to parse this in to Java class which has field of type List class, When JSON data comes with matches as “Object” format, it throws exception “Expected BEGIN_ARRAY but was BEGIN_OBJECT”.

This guy, https://github.com/sacdroid did a Java adapter to Fix it problem.

You can use these classes bellow, then while constructing GSON instance, you have to assign TypeAdapterFactory with ArrayAdapterFactory to GsonBuilder.

Gson gson = new GsonBuilder().registerTypeAdapterFactory(new ArrayAdapterFactory()).create();

ArrayAdapter.java http://sachinpatil.com/downloads/code/ArrayAdapter.java

ArrayAdapterFactory.java http://sachinpatil.com/downloads/code/ArrayAdapterFactory.java

PS: In this case, you had problem with you JSON, your JSON content wasn't a Valid, I fix it putting [ ] (brackets) between the { }'s and ,(comma) to separate :

[{
    "appLoginId": 1058,
    "tabId": "1",
    "elementType": "Image",
    "label": "No Image Name",
    "value": "https://admin.xyz.com",
    "seqTrail": "No possible trail sequence",
    "timeStamp": "2014-01-31 13:02:42.618"
}, {
    "appLoginId": 1058,
    "tabId": "1",
    "elementType": "Image",
    "label": "No Image Name",
    "value": "https://admin.xyz.com/xyz/images/btn-cancel.gif",
    "seqTrail": "No possible trail sequence",
    "timeStamp": "2014-01-31 13:02:42.625"
}]

Upvotes: 1

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