将ArrayList转换为JSON Array，Java编程

Question

Hi there i know maybe this is stupid mistake, but i need your help.

i have code like this that getting an object from db using ArrayList then convert it to JSONArray

protected JSONArray statisticPesanan(){
    List<ListPesanan> det = new ArrayList();
    JSONArray jsonArray = new JSONArray();
    try {
        //create JSONObject to executed
        String sql = "SELECT * FROM vstatisticpesanan";
        Connection conn;
        conn = datman.logOn();
        Statement statement = (Statement) conn.createStatement();
        ResultSet rs = statement.executeQuery(sql);
        //add list to Array
        while (rs.next())
        { 
            ListPesanan psn = new ListPesanan(rs.getString(1), rs.getInt(2));
            det.add(psn);
        }
        //convert to JSON array
        for (int i=0; i < det.size(); i++) {
            jsonArray.add(det.get(i).jsonobject());
        }
    } catch (SQLException se) {
        Logger.getLogger(Analytics.class.getName()).log(Level.SEVERE, null, se);
        java.lang.System.out.println("Error on Analytics Generate JSON Pesanan Statistics : " + se.toString());
    } 
    finally {
        datman.logOff(); 
    }    
    return jsonArray;
}

the output from servlet execution using this code

 public class chartGetTransaction extends HttpServlet {

/**
 * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
 * methods.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    try {
        /* Execution of JSON Chart */
        Analytics show = new Analytics();
        JSONArray array = show.getStatisticPesanan();
        for(int i = 0; i < array.size(); i++){
            out.print(array.get(i).toString());
        }
    } finally {
        out.close();
    }
}

the RESULT OUTPUT is like this:

{"1":"2013-10-12","2":3}{"1":"2013-11-16","2":2}{"1":"2013-12-23","2":4}{"1":"2014-02-11","2":10}

but i need the format like this::

[{"1":"2013-10-12","2":3},{"1":"2013-11-16","2":2},{"1":"2013-12-23","2":4},{"1":"2014-02-11","2":10}]

any ideas guys?

thanks.

Answer 1

A JSONArray contains other json elements. In your case, it seems like it contains json objects.

When you do

JSONArray array = show.getStatisticPesanan();
for(int i = 0; i < array.size(); i++){
    out.print(array.get(i).toString());
}

you are printing (and concatenating) the individuals objects in the array. You don't want this. You want to print the array directly. Fortunately, JSONArray#toString() already does that serialization for you.

JSONArray array = show.getStatisticPesanan();
out.print(array.toString());

Answer 2

Because you are using the for loop

for(int i = 0; i < array.size(); i++){
    out.print(array.get(i).toString());
}

it will print the one - by - one for the requirement format you just have to use the below code..

StringWriter out = new StringWriter();
jsonArray.writeJSONString(out);
String jsonText = out.toString();
out.print(jsonText);