This sample code can be used to download and view a file over a network in a TextBox component Through an httpConnection,

Important Points:

1)   One benefit of using an HttpConnection (as compared to InputStream or StreamConnection) is the availability of a method to check for the length of the remote data. The data can then be read in one fell-swoop, in contrast to reading one character/byte at a time.

2)      Before leaving the viewFile() method, check to the status of the input stream and the httpConnection, and close if necessary. 

3)   This example is written for version 1.0.3 of MIDP and CLDC

 

Java Code:

/*--------------------------------------------------
* 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();
    }	
  }
}

2006-12-12

Comments(4)

1.	It works like a charm. Thanks a lot. By: Balram at 2008-08-22 21:18:44
2.	when i trying to build the above program it is giving warning on my console like "To avoid potential deadlock, operations that may block, such as networking, should be performed in a different thread than the commandAction() handler." and also giving text exception on my emulator like "is it ok to use airtime?" why this is comming please suggest me i need it urgent. thanx in advance By: bhagyalaxmi at 2008-10-10 23:45:45
3.	when i trying this code . i am getting this error java.lang.NoClassDefFoundError: com/sun/kvem/midp/MIDP$KVMInterface at com.sun.kvem.midp.MIDP.run(Unknown Source) at com.sun.kvem.environment.EmulatorInvoker.runEmulatorImpl(Unknown Source) at com.sun.kvem.environment.EmulatorInvoker.runEmulatorSameVM(Unknown Source) at com.sun.kvem.environment.EmulatorInvoker.runEmulator(Unknown Source) at com.sun.kvem.environment.ProfileEnvironment$KVMThread.runEmulator(Unknown Source) at com.sun.kvem.environment.ProfileEnvironment$KVMThread.run(Unknown Source) Caused by: java.lang.ClassNotFoundException: com.sun.kvem.midp.MIDP$KVMInterface at java.net.URLClassLoader$1.run(URLClassLoader.java:197) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 6 more Caused by: java.io.IOException: unexpected EOF at sun.misc.Resource.getBytes(Resource.java:103) at java.net.URLClassLoader.defineClass(URLClassLoader.java:256) at java.net.URLClassLoader.access$000(URLClassLoader.java:56) at java.net.URLClassLoader$1.run(URLClassLoader.java:195) ... 11 more By: sharath at 2010-04-06 00:58:29
4.	Cool! Downloading the whole file with the HttpConnection length method. Nice! By: Luddite at 2010-06-26 12:26:26

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