Question

Hello I’m trying to load my listview with data from a database via a webservice. I have tried to do this in two fold and I am not very confident in each stage.

1. return a list/array from my tomcat here is the code

   String mylist[] = {"", "", "", "", "", ""};
   
   try {
       Class.forName(driver).newInstance();
       con = DriverManager.getConnection(url + db, user, pass);
   
       String query1 = "select username from Users where online = 'yes'";
       PreparedStatement preparedStmt1 = con.prepareStatement(query1);
       ResultSet result1 = preparedStmt1.executeQuery();
   
       int i = 0;
       while (result1.next()) {
           mylist[i] = result1.getString(1);               
       }
   } catch (Exception e1) {
       e1.printStackTrace();
   }
   
   out.println(mylist);
   out.close();
   

My question here would be is this the right way to return a list from a webservice?

1. The second stage is to get the list to my list view, here is my code

   try {
       HttpClient client = new DefaultHttpClient();
       HttpGet request = new HttpGet();
       URI webservice = new URI("http://192.168.0.3:8080/Users/users");
       request.setURI(webservice);
       HttpResponse response = client.execute(request);
   
       BufferedReader rd = new BufferedReader(
               new InputStreamReader(response.getEntity()
                       .getContent()));
   
       while ((rd.readLine()) != null) {
   
           ArrayList<String> list = rd.readLine();
       }
   } catch (Exception e1) {
       e1.printStackTrace();
   }
   

This seems to only work when the webservice returns single lines of text. How do I retrieve something like an array from a Http request?

Thanks!

Answer 1

A WebService can only return xml or string type, so you can put your list into a string with format like this:

"this is a string 1; this is a string 2; this is a string 3"

The server side look like:

  StringBuilder myList = new StringBuilder();

 try {
     Class.forName(driver).newInstance();
     con = DriverManager.getConnection(url + db, user, pass);

     String query1 = "select username from Users where online = 'yes'";
     PreparedStatement preparedStmt1 = con.prepareStatement(query1);
     ResultSet result1 = preparedStmt1.executeQuery();

     int i = 0;
      while (result1.next()) {
          myList.append( result1.getString(1) + ";");               
  }
} catch (Exception e1) {
  e1.printStackTrace();
 }

out.println(mylist.toString());
out.close();

Then from Android client side, you can get it by String.split(“;”);
Here is an example:

private String inputStreamToString(InputStream is)
{
String line = "";
StringBuilder total = new StringBuilder();
// Wrap a BufferedReader around the InputStream
BufferedReader rd = new BufferedReader(new InputStreamReader(is), 1024 * 4);
// Read response until the end
try
{

    while ((line = rd.readLine()) != null)
    {
        total.append(line);
    }
} catch (IOException e)
{
    Log.e(TAG, "error build string" + e.getMessage());
}
// Return full string
return total.toString();
 }

InputStream is = response.getEntity().getContent();
String strResponse = inputStreamToString(is);
String mylist[] = strResponse .split(";");

Or you can use JSON to parse an list object and transfer from WebService to Android client