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;

    }


}