Java JSON Array of String Arrays formatting issue

Question

As the title suggests, I'm having an issue with my JSON formatting for an Array of String Arrays (List)

Basically, this is the format that I would like to see:

{"Item":
    ["Id: 1","Title: Surface Pro 4","Phone: 4077603835","Email:  
    [email protected]","Description: Surface Pro 4 for sale, in  
    excellent condition, basically brand new!"],

"Item":
    "Id: 2","Title: Macbook Air","Phone: null","Email:  
     null","Description: null"],
"Item": 
    "Id: 3","Title: Lenovo Laptop","Phone: 3433215565","Email: 
     XXXXXXXX.com","Description: Free Macbook Air, I promise"]
}

However, this is the below format that my code is producing:

{"Item":["Id: 1","Title: Surface Pro 4","Phone: 4077603835","Email:   
[email protected]","Description: Surface Pro 4 for sale, in  
excellent condition, basically brand new!","Id: 2","Title: Macbook 
Air","Phone: null","Email: null","Description: null","Id: 3","Title: 
Lenovo Laptop","Phone: 3433215565","Email: 
XXXXXXXX.com","Description: Free Macbook Air, I promise"]}

I just want to see separate arrays for each item! I think the issue lies with this part of code: "obj.put("Item", items);" as it's putting all the items in the same array, but how can I dynamically create different arrays? My list of items will keep expanding and will never be constant.

Code:

public List<String[]> SelectAllSQL() {
    List<String[]> result = new ArrayList<String[]>();

    sql = "select * from item";

    try {
        ResultSet rs = stmt.executeQuery(sql);

        rs.last();
        int lastRow = rs.getRow();

        for(int row = 1; row <= lastRow; row++) {
            rs.absolute(row);

            result.add(new String[] {rs.getString("title"),  
                       rs.getString("phone"), rs.getString("email"), 
                       rs.getString("description"), 
                       rs.getString("id")});
        }
        return result;
    } 
    catch (SQLException e) {
        e.printStackTrace();
    }
    return null;
}

public String getIt() {
    ConnectionDB db = new ConnectionDB();
    QueryDB query = new QueryDB();

    List<String[]> sqlResult = new ArrayList<String[]>();

    db.Connect();

    sqlResult = query.SelectAllSQL();

    JSONObject obj = new JSONObject();
    JSONArray items = new JSONArray();

    for(String[] arr : sqlResult) {
        items.add("Id: " + arr[4]);
        items.add("Title: " + arr[0]);
        items.add("Phone: " + arr[1]);
        items.add("Email: " + arr[2]);
        items.add("Description: " + arr[3]);

        obj.put("Item", items);
    }
    return obj.toJSONString();

Place JSONArray items = new JSONArray(); into the scope of for loop. In your case, you are using the same items for all different items. — BrightFlow
– BrightFlow, Commented Nov 17, 2016 at 3:55

Tri Pham · Accepted Answer · 2016-11-17 04:06:06Z

2

I think you're right with that line of code creating problems. You can think of JSON objects containing Key and Value pair. In your case, its "Item" is the Key and the array is the Value. You access JSON objects Values through their Keys, so you can't have Key and Value pairs with the same Key.

Solution: Make your Keys different. "Item1", "Item2", "Item3". Also place JSONArray items = new JSONArray(); in your scope like David says

edited Nov 17, 2016 at 4:06

answered Nov 17, 2016 at 3:54

Tri Pham

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Val H · Accepted Answer · 2016-11-17 03:56:02Z

1

Two things:

Re-initialize the JSONArray for each item inside the loop, so that each row of your sqlResult will have its own array of attributes. The existing code initializes it once, which is how the array in the current output ended up with data from all three in it.
```
for(String[] arr : sqlResult) {
    JSONArray items = new JSONArray();
```
JSONObject does not allow multiple entries with the same key. JSONObject will not allow you have three entries, all with the same value of "Item". When obj.put("Item", items); gets called the second and third time, it replaces the previous value of "Item" instead of making new entries. Two of many possible solutions, both require changing your desired output
- Choose a key that's unique for each record, such as maybe the id
- Create another JSONArray containing the 3+ items instead of having it be an associative JSONObject

answered Nov 17, 2016 at 3:56

Val H

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1 Comment

Jared Hart Over a year ago

Thanks so much, this fixed my issue!!

Monis Majeed · Accepted Answer · 2016-11-17 04:00:48Z

1

JSONArray items = new JSONArray();

Keep it inside the for loop, as it will recreate the JSONArray, otherwise what is happening it is adding to same array as elmenets, so keep it inside the loop

answered Nov 17, 2016 at 4:00

Monis Majeed

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