download and view a file over a network

Ini contoh kode dapat digunakan untuk mendownload dan melihat file melalui jaringan dalam komponen TextBox Melalui sebuah HttpConnection,

Poin Penting:

1) Salah satu manfaat dari menggunakan HttpConnection (dibandingkan dengan InputStream atau StreamConnection) adalah tersedianya metode untuk memeriksa panjang data remote. Data kemudian dapat dibaca dalam satu kali kejadian-, berbeda dengan membaca satu karakter / byte pada suatu waktu.

2) Sebelum meninggalkan metode viewFile (), memeriksa status dari input stream dan HttpConnection itu, dan menutup jika perlu.

3) Contoh ini ditulis untuk versi 1.0.3 dari MIDP dan CLDC

Kode java:

/*————————————————–
* FileViewer.java
*
* Download and view a file over a network
*————————————————-*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;

public class FileViewer extends MIDlet implements CommandListener
{
private Display display; // Reference to Display object
private TextBox tbViewer; // View file contents in a textbox
private Command cmView; // Command to view file
private Command cmExit; // Command to exit
private String url = “http://www.corej2me.com/midpbook_v1e1/scratch/fileViewer.hlp”;

public FileViewer()
{
display = Display.getDisplay(this);

// Define commands
cmView = new Command(”View”, Command.SCREEN, 2);
cmExit = new Command(”Exit”, Command.EXIT, 1);

tbViewer = new TextBox(”Viewer”, “”, 250, TextField.ANY);
tbViewer.addCommand(cmView);
tbViewer.addCommand(cmExit);
tbViewer.setCommandListener(this);
}

public void startApp()
{
display.setCurrent(tbViewer);
}

private void viewFile() throws IOException
{
HttpConnection http = null;
InputStream iStrm = null;

try
{
// Create the connection
http = (HttpConnection) Connector.open(url);

//—————-
// Client Request
//—————-
// 1) Send request method
http.setRequestMethod(HttpConnection.GET);

// 2) Send header information (this header is optional)
http.setRequestProperty(”User-Agent”, “Profile/MIDP-1.0 Configuration/CLDC-1.0?);

// 3) Send body/data – No data for this request

//—————-
// Server Response
//—————-
// 1) Get status Line
System.out.println(”Msg: ” + http.getResponseMessage());
System.out.println(”Code: ” + http.getResponseCode());

// 2) Get header information
if (http.getResponseCode() == HttpConnection.HTTP_OK)
{
// 3) Get data (show the file contents)
iStrm = http.openInputStream();
int length = (int) http.getLength();
if (length > 0)
{
byte serverData[] = new byte[length];
iStrm.read(serverData);
tbViewer.setString(new String(serverData));
}
}
}
finally
{
// Clean up
if (iStrm != null)
iStrm.close();
if (http != null)
http.close();
}
}

public void pauseApp()
{ }

public void destroyApp(boolean unconditional)
{ }

public void commandAction(Command c, Displayable s)
{
if (c == cmView)
{
try
{
viewFile();
}
catch (Exception e)
{
System.out.println(e.toString());
}
}
else if (c == cmExit)
{
destroyApp(false);
notifyDestroyed();
}
}
}