[冷枫]在无线J2ME设备上实现超文本传输协议

/*
* HttpMidlet.java
*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;


public class HttpMidlet extends MIDlet implements CommandListener {
//使用默认的URL。用户可以从图形用户接口改变这个值
private static String defaultURL = "http://localhost:8080/test/servlet/EchoServlet";

// 主MIDP 显示
private Display myDisplay = null;

// 输入URL的图形用户接口组件
private Form requestScreen;
private TextField requestField;

// 用于提交请求的图形用户接口组件
private List list;
private String[] menuItems;

// 用于显示服务器响应的图形用户接口组件
private Form resultScreen;
private StringItem resultField;

//用于requestScreen的"send"按钮
Command sendCommand;
// 用于requestScreen的"exit"按钮
Command exitCommand;
// 用于requestScreen的"back"按钮
Command backCommand;

public HttpMidlet(){
// 初始化图形用户接口组件
myDisplay = Display.getDisplay( this );
sendCommand = new Command( "SEND", Command.OK, 1 );
exitCommand = new Command( "EXIT", Command.OK, 1 );
backCommand = new Command( "BACK", Command.OK, 1 );

//显示请求的URL
requestScreen = new Form( "Type in a URL:" );
requestField = new TextField( null, defaultURL, 100, TextField.URL );
requestScreen.append( requestField );
requestScreen.addCommand( sendCommand );
requestScreen.addCommand( exitCommand );
requestScreen.setCommandListener( this );

// 选择想要的HTTP请求方法
menuItems = new String[] {"GET Request", "POST Request"};
list = new List( "Select an HTTP method:", List.IMPLICIT, menuItems, null );
list.setCommandListener( this );

// 先是从服务器上收到的信息
resultScreen = new Form( "Server Response:" );
resultScreen.addCommand( backCommand );
resultScreen.setCommandListener( this );

}//结束HttpMidlet()

public void startApp() {
myDisplay.setCurrent( requestScreen );
}//结束 startApp()

public void commandAction( Command com, Displayable disp ) {
// 当用户点击"send"按钮
if ( com == sendCommand ) {
myDisplay.setCurrent( list );
} else if ( com == backCommand ) {
requestField.setString( defaultURL );
myDisplay.setCurrent( requestScreen );
} else if ( com == exitCommand ) {
destroyApp( true );
notifyDestroyed();
}//结束 if ( com == sendCommand )

if ( disp == list && com == List.SELECT_COMMAND ) {

String result;

if ( list.getSelectedIndex() == 0 ) // 发送一个 GET 请求到服务器
result = sendHttpGet( requestField.getString() );
else // 发送一个 POST 请求到服务器
result = sendHttpPost( requestField.getString() );

resultField = new StringItem( null, result );
resultScreen.append( resultField );
myDisplay.setCurrent( resultScreen );
}//结束if ( dis == list && com == List.SELECT_COMMAND )
}//结束 commandAction( Command, Displayable )

private String sendHttpGet( String url )
{
HttpConnection hcon = null;
DataInputStream dis = null;
StringBuffer responseMessage = new StringBuffer();

try {
//使用READ权限的标准的 HttpConnection
hcon = ( HttpConnection )Connector.open( url );

//从HttpConnection取得一个 DataInputStream
dis = new DataInputStream( hcon.openInputStream() );

// 从服务器上取回响应
int ch;
while ( ( ch = dis.read() ) != -1 ) {
responseMessage.append( (char) ch );
}//结束while ( ( ch = dis.read() ) != -1 )
}
catch( Exception e )
{
e.printStackTrace();
responseMessage.append( "ERROR" );
} finally {
try {
if ( hcon != null ) hcon.close();
if ( dis != null ) dis.close();
} catch ( IOException ioe ) {
ioe.printStackTrace();
}//结束try/catch
}//结束try/catch/finally
return responseMessage.toString();
}//结束sendHttpGet( String )

private String sendHttpPost( String url )
{
HttpConnection hcon = null;
DataInputStream dis = null;
DataOutputStream dos = null;
StringBuffer responseMessage = new StringBuffer();
// 请求体
String requeststring = "This is a POST.";

try {
// 使用读写权限的 HttpConnection
hcon = ( HttpConnection )Connector.open( url, Connector.READ_WRITE );

//设置请求方法为POST
hcon.setRequestMethod( HttpConnection.POST );

// 取得发送请求字符串的DataOutputStream
dos = hcon.openDataOutputStream();
byte[] request_body = requeststring.getBytes();

// 发送请求字符串到服务器
for( int i = 0; i < request_body.length; i++ ) {
dos.writeByte( request_body[i] );
}//结束 for( int i = 0; i < request_body.length; i++ )

// 取得做为接收服务器响应的DataInputStream
dis = new DataInputStream( hcon.openInputStream() );

// 从服务器上取回响应
int ch;
while( ( ch = dis.read() ) != -1 ) {
responseMessage.append( (char)ch );
}//结束while( ( ch = dis.read() ) != -1 ) {
}
catch( Exception e )
{
e.printStackTrace();
responseMessage.append( "ERROR" );
}
finally {
// 释放输入输出流和HTTP连接
try {
if( hcon != null ) hcon.close();
if( dis != null ) dis.close();
if( dos != null ) dos.close();
} catch ( IOException ioe ) {
ioe.printStackTrace();
}//结束try/catch
}//结束try/catch/finally
return responseMessage.toString();
}//结束sendHttpPost( String )

public void pauseApp() {
}//结束pauseApp()

public void destroyApp( boolean unconditional ) {
myDisplay = null;
requestScreen = null;
requestField = null;
resultScreen = null;
resultField = null;
}//结束 destroyApp( boolean )
}//结束HttpMidlet