How to convert this json String to normal java arraylist using gson

Question

I tried to convert following JSON string into Array and got following error:

Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory at net.sf.json.AbstractJSON.(AbstractJSON.java:54) at net.sf.json.util.CycleDetectionStrategy.(CycleDetect‌ionStrategy.java:36) at net.sf.json.JsonConfig.(JsonConfig.java:65) at net.sf.json.JSONSerializer.toJSON(JSONSerializer.java:84)

JSON:

[  
   {  
      "file_name":"1.xml",
      "file_ext":"application/octet-stream",
      "sr_no":"0.1",
      "status":"Checked ",
      "rev":"1",
      "locking":"0"
   },
   {  
      "file_name":"2.xml",
      "file_ext":"json/octet-stream",
      "sr_no":"0.2",
      "status":"Not Checked ",
      "rev":"2",
      "locking":"1"
   },
   {  
      "file_name":"3.xml",
      "file_ext":"application/json-stream",
      "sr_no":"0.3",
      "status":"Checked ",
      "rev":"1",
      "locking":"3"
   },
   {  
      "file_name":"4.xml",
      "file_ext":"application/octet-stream",
      "sr_no":"0.4",
      "status":"Checked ",
      "rev":"0.4",
      "locking":"4"
   }
]

Code:

JSONArray nameArray = (JSONArray) JSONSerializer.toJSON(output);
System.out.println(nameArray.size());
for(Object js : nameArray)
{
    JSONObject json = (JSONObject) js;
    System.out.println("File_Name :" +json.get("file_name"));                                         
}

I'm voting to close this question as off-topic because this isn't even a question but a work request. — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Sep 23, 2016 at 9:23
At least show your current work, and tell us what problems you're having with it. Don't post a lazy question that shows no evidence of effort — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Sep 23, 2016 at 9:24
Sorry to say but this is not work request actually i have tried the answer and got exception Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory at net.sf.json.AbstractJSON.<clinit>(AbstractJSON.java:54) at net.sf.json.util.CycleDetectionStrategy.<clinit>(CycleDetectionStrategy.java:36) at net.sf.json.JsonConfig.<clinit>(JsonConfig.java:65) at net.sf.json.JSONSerializer.toJSON(JSONSerializer.java:84) — user6773905
– user6773905, Commented Sep 23, 2016 at 9:44

Community · Accepted Answer · 2020-06-20 09:12:55Z

I know the question is about converting JSON String to Java Array, but I would like to also answer about how to convert the JSON String to an ArrayList using the Gson Library.

Since I spend a good amount of time in solving this, I hope my solution may help others.

My JSON string looks similar to this one -

I had an object named StockHistory, and I wanted to convert this JSON into an ArrayList of StockHistory.

This is how my StockHistory class looked -

class StockHistory {    
 Date date;
 Double open;
 Double high;
 Double low;
 Double close;
 Double adjClose;
 Double volume;
}

The code that I used to convert the JSON Array to the ArrayList of StockHistory is as follows -

Gson gson = new Gson();
Type listType = new TypeToken< ArrayList<StockHistory> >(){}.getType();
List<StockHistory> history = gson.fromJson(reader, listType);

Now if you are reading your JSON from a file, the reader's initialization would be -

Reader reader = new FileReader(fileName);

and if you are just converting a string to JSON object then, the reader's initialization would simply be -

String reader = "{ // json String }";

Hope that helps. Cheers!!!

Numb · Accepted Answer · 2016-09-23 10:29:59Z

2

You can create a java class with entities are: file_name, file_ext, sr_no, status, rev, locking in string type.

 public class TestJson {

        private String file_name, file_ext, sr_no, status, rev, locking;

        //get & set
        }
}

Then you call:

public static void main(String[] args) {
    String json = your json string;
    TestJson[] respone = new Gson().fromJson(json, TestJson[].class);
    for (TestJson s : respone) {
       System.out.println("File name: " + s.getFile_name());
    }
}

So, you have a list of object you want.

edited Sep 23, 2016 at 10:29

answered Sep 23, 2016 at 10:23

Numb

1553 bronze badges

2 Comments

user6773905 Over a year ago

can u please help me with example as i have created the class jut wan to know how to get list of object through code.

Numb Over a year ago

i'm not really to understand your mean, can u talk your mean clearly more?

Cong Wang · Accepted Answer · 2016-09-23 09:41:57Z

0

Firstly I have to say your question is quite "ugly" and next time please improve your question's quality.

Answer:

Try to use com.fasterxml.jackson.databind.ObjectMapper

If you have a java class to describe your items in the list:

final ObjectMapper mapper = new ObjectMapper();
YourClass[] yourClasses = mapper.readValue(YourString, YourClass[].class);

Then convert the array to a List.

If you don't have a java class, just you LinkedHashMap instead.

answered Sep 23, 2016 at 9:41

Cong Wang

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1 Comment

Cong Wang Over a year ago

GSON also has a formJson() method

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