J2ME实现从服务器端下载文件(J2me for HttpConnection)

J2ME实现从服务器端下载文件:
我以下载服务器文件并在手机客户端显示图片为例：

测试截图：

程序代码

package com.mopietek;

import java.io.IOException;
import java.io.InputStream;

import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.StringItem;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class HttpMID extends MIDlet implements CommandListener,Runnable{

	public static Command connect = new Command ("联网",Command.OK,1);
	public static Command change = new Command("更改入网的方式",Command.OK,1);
	public static Command exit = new Command("退出",Command.EXIT,1);
	
	public Form form;
	public Display display;
	
	HttpConnection http;
	
	String host = "dev.mopietek.net:8080/ebook";
	String path = "/upload/123.gif";
	//接入点为cmnet或者是cmwap
	boolean cmnet = true;
	
	public static final int WAIT = 0;  //等待
	public static final int CONNECT = 1; //连接中
	public static final int SUCCESS = 2; //成功
	public static final int FALL = 3; //失败
	public int state; //当前状态
	
	StringBuffer sb = new StringBuffer("当前接入方式为:CMNET\n");
	StringItem si = new StringItem(null,sb.toString());
	
	
	public HttpMID(){
		
		display = Display.getDisplay(this);
	    state = WAIT;
	    
		form = new Form("HttpTest");
	    form.append(si);
	    form.addCommand(connect);
	    form.addCommand(change);
	    form.addCommand(exit);
	    form.setCommandListener(this);
	    
	}
	
	protected void destroyApp(boolean unconditional)
			throws MIDletStateChangeException {
		// TODO Auto-generated method stub
		
	}

	protected void pauseApp() {
		// TODO Auto-generated method stub
		
	}

	protected void startApp() throws MIDletStateChangeException {

		display.setCurrent(form);
	}

	public void commandAction(Command c, Displayable d) {

		if(c == change){
			if(isConnect())
				return;
			cmnet = ! cmnet;
			form.deleteAll();
			
			sb.delete(0, sb.length());
			addStr("当前接入方式为:" + (cmnet ? "CMNET" : "CMWAP"));
			form.append(si);
			
		}
		else if(c == connect){
			if(isConnect())
				return;
			new Thread(this).start();
			
		}else if(c == exit){
			
			try {
				destroyApp(true);
			} catch (MIDletStateChangeException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			this.notifyDestroyed();
		}
		
	}

	
	
	private boolean isConnect() {
		
		if(state == CONNECT){
		   addStr("网络链接中,请稍后...");
		   return true;
		}
		return false;
	}

	private void addStr(String str) {
		
		sb.append(str + "\n");
		si.setText(sb.toString());
	}

	public void run() {

		form.deleteAll();
		
		sb.delete(0, sb.length());
		addStr("当前接入方式为:" +(cmnet ? "CMNET" : "CMWAP"));
		form.append(si);
		state = CONNECT;
		addStr("网络链接中..");
		
		InputStream is = null;
		
		try{
			
			String url = null;
			url = cmnet ? ("http://" + host + path) : ("http://10.0.0.172:80" +path);
			
			http = (HttpConnection) Connector.open(url,Connector.READ_WRITE,true);
			
			if(!cmnet)
			   
				http.setRequestProperty("X-Online-Host", host);
			    http.setRequestMethod(HttpConnection.GET);
			    String contentType = http.getHeaderField("Content-Type");
			    System.out.println(contentType);
			    if(contentType != null && contentType.indexOf("text/vnd.wap.wml") != -1){
			    	
			    	 addStr("移动资费页面，过滤");
			    	 http.close();
			    	 http = null;
			    	 http = (HttpConnection) Connector.open(url,Connector.READ_WRITE,true);
			    
			    	 if(!cmnet)
			    		 http.setRequestProperty("X-Online-Host", host);
			    	     http.setRequestMethod(HttpConnection.GET);
			    	     contentType = http.getHeaderField("Content-Type");
			    }
			    
			    addStr("Content-Type=" + contentType);
			    int code = http.getResponseCode();
			    addStr("HTTP Code :" + code);
			    if(code == 200){
			    	addStr("网络联网成功，接收数据...");
			    	is = http.openInputStream();
			    	Image image = Image.createImage(is);
			    	addStr("数据接收完毕，显示图片...");
			    	form.append(image);
			    	
			    	state = SUCCESS;
			    	return;
			    }else{
			    	addStr("访问页面失败");
			    }
		}catch(IOException e){
			addStr("联网发生异常：" + e.toString());
			e.printStackTrace();
		}catch(Exception ee){
			addStr("发生异常:" +ee.toString());
			ee.printStackTrace();
		}finally{
			if(is != null){
				try{
					is.close();
				}catch(IOException e){
					e.printStackTrace();
				}
				is = null;
			}
			
			if(http != null)
				try{
				     http.close();	
				}catch(IOException e){
					e.printStackTrace();
				}
				http = null;
			}
			state = FALL;
		
	}
	

}