Java Tutorial/J2ME/HttpConnection

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An example MIDlet to fetch a page using an HttpConnection

   <source lang="java">

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* may be used to endorse or promote products derived from this software
* without specific prior written permission.
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* This software is provided "AS IS," without a warranty of any kind. ALL
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* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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import java.io.IOException; import java.io.InputStream; import javax.microedition.io.Connector; import javax.microedition.io.HttpConnection; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.TextBox; import javax.microedition.midlet.MIDlet; /** 

* An example MIDlet to fetch a page using an HttpConnection.
*/

public class J2MESecondExample extends MIDlet { 

 private Display display;
 private String url = "http://www.y.ru/hello.txt";
 public J2MESecondExample() {
   display = Display.getDisplay(this);
 }
 /**
  * This will be invoked when we activate the MIDlet.
  */
 public void startApp() {
   // Use the specified URL is overriden in the descriptor
   try {
     downloadPage(url);
   } catch (IOException e) {
     // handle the exception
   }
 }
 private void downloadPage(String url) throws IOException {
   StringBuffer b = new StringBuffer();
   InputStream is = null;
   HttpConnection c = null;
   TextBox t = null;
   try {
     long len = 0;
     int ch = 0;
     c = (HttpConnection) Connector.open(url);
     is = c.openInputStream();
     len = c.getLength();
     if (len != -1) {
       // Read exactly Content-Length bytes
       for (int i = 0; i < len; i++)
         if ((ch = is.read()) != -1)
           b.append((char) ch);
     } else {
       // Read till the connection is closed.
       while ((ch = is.read()) != -1) {
         len = is.available();
         b.append((char) ch);
       }
     }
     t = new TextBox("hello again....", b.toString(), 1024, 0);
   } finally {
     is.close();
     c.close();
   }
   display.setCurrent(t);
 }
 /**
  * Pause, discontinue....
  */
 public void pauseApp() {
 }
 /**
  * Destroy must cleanup everything.
  */
 public void destroyApp(boolean unconditional) {
 }

}</source>





An example MIDlet to invoke a CGI script (POST method is used).

   <source lang="java">

import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import javax.microedition.io.Connector; import javax.microedition.io.HttpConnection; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.TextBox; import javax.microedition.midlet.MIDlet; public class InvokeCgiMidlet2 extends MIDlet { 

 private Display display;
 String url = "http://www.g.ru/get.cgi";
 public InvokeCgiMidlet2() {
   display = Display.getDisplay(this);
 }
 public void startApp() {
   try {
     getGrade(url);
   } catch (IOException e) {
     e.printStackTrace();
   }
 }
 public void pauseApp() {
 }
 public void destroyApp(boolean unconditional) {
 }
 void getGrade(String url) throws IOException {
   HttpConnection c = null;
   InputStream is = null;
   OutputStream os = null;
   StringBuffer b = new StringBuffer();
   TextBox t = null;
   try {
     c = (HttpConnection) Connector.open(url);
     c.setRequestMethod(HttpConnection.POST);
     c.setRequestProperty("CONTENT-TYPE", "application/x-www-form-urlencoded");
     c.setRequestProperty("User-Agent", "Profile/MIDP-1.0 Confirguration/CLDC-1.0");
     c.setRequestProperty("Content-Language", "en-CA");
     os = c.openOutputStream();
     String str = "name=1";
     byte postmsg[] = str.getBytes();
     for (int i = 0; i < postmsg.length; i++) {
       os.write(postmsg[i]);
     }
     os.flush();
     is = c.openDataInputStream();
     int ch;
     while ((ch = is.read()) != -1) {
       b.append((char) ch);
     }
     t = new TextBox("Final Grades", b.toString(), 1024, 0);
   } 
   display.setCurrent(t);
 }

}</source>





Load Image with HttpConnection

   <source lang="java">

import java.io.DataInputStream; import java.io.IOException; import javax.microedition.io.Connector; import javax.microedition.io.HttpConnection; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.Image; import javax.microedition.lcdui.ImageItem; import javax.microedition.lcdui.Item; import javax.microedition.lcdui.StringItem; import javax.microedition.midlet.MIDlet; public class ImageLoaderMIDlet extends MIDlet { 

 private Item mItem;
 public void startApp() {
   final Display display = Display.getDisplay(this);
   Form mainForm = new Form("Loading...");
   display.setCurrent(mainForm);
   final Form imageForm = new Form("Image");
   imageForm.addCommand(new Command("Exit", Command.EXIT, 0));
   imageForm.setCommandListener(new CommandListener() {
     public void commandAction(Command c, Displayable s) {
       notifyDestroyed();
     }
   });
   Thread t = new Thread() {
     public void run() {
       try {
         String URL = "http://localhost/Duke.png";
         Image image = loadImage(URL);
         mItem = new ImageItem(null, image, 0, null);
       } catch (IOException ioe) {
         mItem = new StringItem(null, ioe.toString());
       }
       imageForm.append(mItem);
       display.setCurrent(imageForm);
     }
   };
   t.start();
 }
 public Image loadImage(String url) throws IOException {
   HttpConnection hpc = null;
   DataInputStream dis = null;
   try {
     hpc = (HttpConnection) Connector.open(url);
     int length = (int) hpc.getLength();
     byte[] data = new byte[length];
     dis = new DataInputStream(hpc.openInputStream());
     dis.readFully(data);
     return Image.createImage(data, 0, data.length);
   } finally {
     if (hpc != null)
       hpc.close();
     if (dis != null)
       dis.close();
   }
 }
 public void pauseApp() {
 }
 public void destroyApp(boolean unconditional) {
 }

}</source>





Response Header

   <source lang="java">

import java.io.IOException; import javax.microedition.io.Connector; import javax.microedition.io.HttpConnection; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.DateField; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.StringItem; import javax.microedition.lcdui.TextField; import javax.microedition.midlet.MIDlet; public class ResponseHeaderMIDlet extends MIDlet implements CommandListener { 

 private Command exitCommand = new Command("Exit", Command.EXIT, 1);
 private Command sendCommand = new Command("Send", Command.OK, 1);
 private Command backCommand = new Command("Upload", Command.OK, 1);
 private Display display;
 private String defaultURL = "http://localhost/";
 private Form mainForm, resultForm;
 private TextField URL;
 private DateField DateField1 = new DateField("Date", DateField.DATE_TIME);
 private DateField DateField2 = new DateField("Expiration", DateField.DATE_TIME);
 private DateField DateField3 = new DateField("Last Modified", DateField.DATE_TIME);
 private StringItem resultItem;
 public ResponseHeaderMIDlet() {
   display = Display.getDisplay(this);
 }
 public void startApp() {
   URL = new TextField(null, defaultURL, 250, TextField.URL);
   mainForm = new Form("Test");
   mainForm.append(URL);
   mainForm.addCommand(sendCommand);
   mainForm.addCommand(exitCommand);
   mainForm.setCommandListener(this);
   display.setCurrent(mainForm);
 }
 public void pauseApp() {
 }
 public void destroyApp(boolean unconditional) {
 }
 public void commandAction(Command c, Displayable s) {
   if (c == sendCommand) {
     String result = "";
     resultItem = new StringItem(null, result);
     resultForm = new Form("");
     String URLString = URL.getString();
     try {
       result = requestUsingGET(URLString);
     } catch (IOException e) {
       result = "Falied";
     }
     resultItem.setText(result);
     resultForm.append(resultItem);
     resultForm.append(DateField1);
     resultForm.append(DateField2);
     resultForm.append(DateField3);
     resultForm.addCommand(backCommand);
     resultForm.setCommandListener(this);
     display.setCurrent(resultForm);
   } else if (c == backCommand) {
     URL.setString(defaultURL);
     display.setCurrent(mainForm);
   } else {
     destroyApp(false);
     notifyDestroyed();
   }
 }
 private String requestUsingGET(String URLString) throws IOException {
   HttpConnection hpc = null;
   String content = "";
   try {
     hpc = (HttpConnection) Connector.open(URLString);
     int status = hpc.getResponseCode();
     if (status != HttpConnection.HTTP_OK)
       content = "Falied";
     else {
       DateField1.setDate(new java.util.Date(hpc.getDate()));
       DateField2.setDate(new java.util.Date(hpc.getExpiration()));
       DateField3.setDate(new java.util.Date(hpc.getLastModified()));
       content += "Content Type: " + hpc.getType() + "\n";
       content += "Content Length: " + hpc.getLength() + "\n";
       content += "Contnet Encoding: " + hpc.getEncoding() + "\n";
     }
     if (hpc != null)
       hpc.close();
   } catch (IOException e2) {
   }
   return content;
 }

}</source>





Use HttpConnection

   <source lang="java">

import java.io.InputStream; import java.io.IOException; import java.io.OutputStream; import javax.microedition.io.Connector; import javax.microedition.io.HttpConnection; import javax.microedition.lcdui.Alert; import javax.microedition.lcdui.AlertType; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.StringItem; import javax.microedition.lcdui.TextField; import javax.microedition.midlet.MIDlet; import javax.microedition.midlet.MIDletStateChangeException; public class HttpMIDlet extends MIDlet implements CommandListener, Runnable { 

 private Display display;
 private Form addressForm = new Form("HTTP Client");
 private Form connectForm = new Form("Connecting");
 private Form displayForm = new Form("Server Reply");
 private TextField serverURL = new TextField("URL:", "", 256, TextField.ANY);
 private StringItem messageLabel = new StringItem(null, "Connecting...\nPlease wait.");
 private Command okCommand = new Command("OK", Command.OK, 0);
 private Command exitCommand = new Command("Exit", Command.EXIT, 0);
 private Command backCommand = new Command("Back", Command.BACK, 0);
 
 protected void startApp() throws MIDletStateChangeException {
   display = Display.getDisplay(this);
   addressForm.append(serverURL);
   addressForm.addCommand(okCommand);
   addressForm.addCommand(exitCommand);
   addressForm.setCommandListener(this);
   connectForm.append(messageLabel);
   connectForm.addCommand(backCommand);
   connectForm.setCommandListener(this);
   displayForm.append(messageLabel);
   displayForm.addCommand(backCommand);
   displayForm.setCommandListener(this);
   display.setCurrent(addressForm);
 }
 protected void pauseApp() {
 }
 protected void destroyApp(boolean unconditional)
     throws MIDletStateChangeException {
 }
 public void commandAction(Command cmd, Displayable d) {
   if (cmd == okCommand) {
     Thread t = new Thread(this);
     t.start();
     display.setCurrent(connectForm);
   } else if (cmd == backCommand) {
     display.setCurrent(addressForm);
   } else if (cmd == exitCommand) {
     try {
       destroyApp(true);
     } catch (MIDletStateChangeException ex) {
     }
     notifyDestroyed();
   }
 }
 public void run() {
   InputStream is = null;
   HttpConnection conn = null;
   try {
     String url = serverURL.getString();
     if (!url.startsWith("http://") && !url.startsWith("https://")) {
       url = "http://" + url;
     }
     conn = (HttpConnection) Connector.open(url, Connector.READ_WRITE);
     if (conn.getResponseCode() == HttpConnection.HTTP_OK) {
       is = conn.openInputStream();
       final int MAX_LENGTH = 128;
       byte[] buf = new byte[MAX_LENGTH];
       int total = 0;
       while (total < MAX_LENGTH) {
         int count = is.read(buf, total, MAX_LENGTH - total);
         if (count < 0) {
           break;
         }
         total += count;
       }
       is.close();
       String reply = new String(buf, 0, total);
       messageLabel.setText(reply);
     } else {
       messageLabel.setText("Failed: error " + conn.getResponseCode() + "\n"+ conn.getResponseMessage());
     }
     conn.close();
     display.setCurrent(displayForm);
   } catch (IOException ex) {
     System.out.println(ex);
     ex.printStackTrace();
     Alert alert = new Alert("I/O Error","An error occurred while communicating with the server.", null,AlertType.ERROR);
     alert.setTimeout(Alert.FOREVER);
     display.setCurrent(alert, addressForm);
     return;
   }
 }

}</source>


Источник — «http://www.jexp.ru/index.php?title=Java_Tutorial/J2ME/HttpConnection&oldid=4077»