issue with parsing JSON Data in Blackberry - blackberry

Question

I am new in BB trying to parse Json file and just want to print the Json responce in a Dialog. But it raises an error regarding No Application Instance and is also getting IllegalStateException. I use GET url method for it.
I Have also add permission in UiApplication like ..
UIApplicationScreen
public static void main(String[] args) {
ApplicationPermissions permRequest = ApplicationPermissionsManager.getInstance().getApplicationPermissions();
permRequest = new ApplicationPermissions();
permRequest.addPermission( ApplicationPermissions.PERMISSION_INTERNET );
ApplicationPermissionsManager.getInstance().invokePermissionsRequest( permRequest );
UiFunApplication app = new UiFunApplication();
app.enterEventDispatcher();
Here is MainScreen Code....
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Vector;
import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
import net.rim.device.api.applicationcontrol.ApplicationPermissions;
import net.rim.device.api.applicationcontrol.ApplicationPermissionsManager;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.container.MainScreen;
import com.rim.samples.jsonme.cakeorder.org.json.me.JSONArray;
import com.rim.samples.jsonme.cakeorder.org.json.me.JSONObject;
public class UiMainscreen extends MainScreen {
public UiMainscreen() {
Dialog.alert("asdasd");
HttpConnection conn = null;
InputStream in = null;
ByteArrayOutputStream out = null;
try {
// String url = "http://api.twitter.com/1/users/show.json?screen_name=Kaka";
String url = "http://docs.blackberry.com/sampledata.json";
conn = (HttpConnection) Connector.open(url, Connector.READ);
conn.setRequestMethod(HttpConnection.GET);
int code = conn.getResponseCode();
if (code == HttpConnection.HTTP_OK) {
in = conn.openInputStream();
out = new ByteArrayOutputStream();
byte[] buffer = new byte[in.available()];
int len = 0;
while ((len = in.read(buffer)) > 0) {
out.write(buffer);
}
out.flush();
String response = new String(out.toByteArray());
Dialog.alert("response is ::"+response);
} catch (Exception e) {
Dialog.alert(e.getMessage());
} finally {
if (out != null) {
try {
out.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Dialog.alert(e.getMessage());
}
}
if (in != null) {
try {
in.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Dialog.alert(e.getMessage());
}
}
if (conn != null) {
try {
conn.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Dialog.alert(e.getMessage());
}
}
}
}
}
Update::
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Vector;
import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
import net.rim.device.api.applicationcontrol.ApplicationPermissions;
import net.rim.device.api.applicationcontrol.ApplicationPermissionsManager;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.CheckboxField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.container.MainScreen;
import com.rim.samples.jsonme.cakeorder.org.json.me.JSONArray;
import com.rim.samples.jsonme.cakeorder.org.json.me.JSONObject;
public class UiMainscreen extends MainScreen implements FieldChangeListener {
public UiMainscreen() {
ButtonField loginButton;
loginButton = new ButtonField("Go", ButtonField.CONSUME_CLICK);
loginButton.setChangeListener(this);
add(loginButton);
}
public void fieldChanged(Field field, int context) {
// TODO Auto-generated method stub
if (field instanceof ButtonField) {
Dialog.alert("Message");
HttpConnection conn = null;
InputStream in = null;
ByteArrayOutputStream out = null;
try {
// String url =
// "http://api.twitter.com/1/users/show.json?screen_name=Kaka";
String url = "http://docs.blackberry.com/sampledata.json";
conn = (HttpConnection) Connector.open(url, Connector.READ);
conn.setRequestMethod(HttpConnection.GET);
int code = conn.getResponseCode();
if (code == HttpConnection.HTTP_OK) {
in = conn.openInputStream();
out = new ByteArrayOutputStream();
byte[] buffer = new byte[in.available()];
int len = 0;
while ((len = in.read(buffer)) > 0) {
out.write(buffer);
}
out.flush();
String response = new String(out.toByteArray());
Dialog.alert("response is ::" + response);
/*
* JSONObject resObject = new JSONObject(response); String
* key = resObject.getString("vehicleType");
*
* Vector resultsVector = new Vector(); JSONArray jsonArray
* = resObject.getJSONArray("name"); if (jsonArray.length()
* > 0) { for (int i = 0; i < jsonArray.length();i++) {
* Vector elementsVector = new Vector(); JSONObject jsonObj
* = jsonArray.getJSONObject(i);
* elementsVector.addElement(jsonObj
* .getString("experiencePoints"));
* elementsVector.addElement
* (jsonObj.getString("Insert Json Array Element Key2"));
* resultsVector.addElement(elementsVector); } }
*/
}
} catch (Exception e) {
Dialog.alert(e.getMessage());
} finally {
if (out != null) {
try {
out.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Dialog.alert(e.getMessage());
}
}
if (in != null) {
try {
in.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Dialog.alert(e.getMessage());
}
}
if (conn != null) {
try {
conn.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Dialog.alert(e.getMessage());
}
}
}
}
}
}

Answer 1

Try this code -
final ButtonField b=new ButtonField("JSON");
add(b);
FieldChangeListener listener=new FieldChangeListener() {
public void fieldChanged(Field field, int context) {
if(field==b){
try {
String httpURL = "http://docs.blackberry.com/sampledata.json";
HttpConnection httpConn;
httpConn = (HttpConnection) Connector.open(httpURL);
httpConn.setRequestMethod(HttpConnection.POST);
DataOutputStream _outStream = new DataOutputStream(httpConn.openDataOutputStream());
byte[] request_body = httpURL.getBytes();
for (int i = 0; i < request_body.length; i++) {
_outStream.writeByte(request_body[i]);
}
DataInputStream _inputStream = new DataInputStream(
httpConn.openInputStream());
StringBuffer _responseMessage = new StringBuffer();
int ch;
while ((ch = _inputStream.read()) != -1) {
_responseMessage.append((char) ch);
}
String res = (_responseMessage.toString());
String responce = res.trim();
Dialog.alert(responce);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
};
b.setChangeListener(listener);