Java实现ftp功能(源程序)

import sun.net.ftp.*;
import sun.net.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.io.*;

public class FtpApplet extends Applet
{
FtpClient aftp;
DataOutputStream outputs ;
TelnetInputStream ins;
TelnetOutputStream outs;
TextArea lsArea;
Label    LblPrompt;
Button   BtnConn;
Button   BtnClose;
TextField  TxtUID;
TextField  TxtPWD;
TextField  TxtHost;
int ch;
public String a="没有连接主机";
        String hostname="";
public void init () {
setBackground(Color.white);
setLayout(new GridBagLayout());
GridBagConstraints GBC = new GridBagConstraints();
LblPrompt = new Label("没有连接主机");
LblPrompt.setAlignment(Label.LEFT);

BtnConn = new Button("连接");
BtnClose = new Button("断开");
BtnClose.enable(false);
TxtUID = new TextField("",15);
TxtPWD = new TextField("",15);
TxtPWD.setEchoCharacter(’*’);
TxtHost = new TextField("",20);
Label LblUID = new Label("User ID:");
Label LblPWD = new Label("PWD:");
Label LblHost = new Label("Host:");

lsArea = new TextArea(30,80);
lsArea.setEditable(false);

GBC.gridwidth= GridBagConstraints.REMAINDER;
GBC.fill     = GridBagConstraints.HORIZONTAL;
((GridBagLayout)getLayout()).setConstraints(LblPrompt,GBC);
add(LblPrompt);

GBC.gridwidth=1;
((GridBagLayout)getLayout()).setConstraints(LblHost,GBC);
add(LblHost);
GBC.gridwidth=GridBagConstraints.REMAINDER;
((GridBagLayout)getLayout()).setConstraints(TxtHost,GBC);
add(TxtHost);

GBC.gridwidth=1;
((GridBagLayout)getLayout()).setConstraints(LblUID,GBC);
add(LblUID);
GBC.gridwidth=1;
((GridBagLayout)getLayout()).setConstraints(TxtUID,GBC);
add(TxtUID);

GBC.gridwidth=1;
((GridBagLayout)getLayout()).setConstraints(LblPWD,GBC);
add(LblPWD);
GBC.gridwidth=1;
((GridBagLayout)getLayout()).setConstraints(TxtPWD,GBC);
add(TxtPWD);

GBC.gridwidth=1;
GBC.weightx=2;
((GridBagLayout)getLayout()).setConstraints(BtnConn,GBC);
add(BtnConn);
GBC.gridwidth=GridBagConstraints.REMAINDER;

((GridBagLayout)getLayout()).setConstraints(BtnClose,GBC);
add(BtnClose);

GBC.gridwidth=GridBagConstraints.REMAINDER;
GBC.fill     = GridBagConstraints.HORIZONTAL;
((GridBagLayout)getLayout()).setConstraints(lsArea,GBC);
add(lsArea);
        }

public boolean connect(String hostname, String uid,String pwd)
{
                this.hostname = hostname;
LblPrompt.setText("正在连接，请等待.....");
try{
  aftp =new FtpClient(hostname);
  aftp.login(uid,pwd);
  aftp.binary();
  showFileContents();
}
catch(FtpLoginException e){
a="无权限与主机:"+hostname+"连接!";
LblPrompt.setText(a);
return false;
}
catch (IOException e){
a="连接主机:"+hostname+"失败!";
LblPrompt.setText(a);
return false;
}
catch(SecurityException e)
{
a="无权限与主机:"+hostname+"连接!";
LblPrompt.setText(a);
return false;
}
LblPrompt.setText("连接主机:"+hostname+"成功!");
return true;
}

public void stop()
{
try
{
aftp.closeServer();
}
catch(IOException e)
{
}
}

public void paint(Graphics g){
}

public boolean action(Event evt,Object obj)
{
if (evt.target == BtnConn)
{
LblPrompt.setText("正在连接，请等待.....");
if (connect(TxtHost.getText(),TxtUID.getText(),TxtPWD.getText()))
{
BtnConn.setEnabled(false);
BtnClose.setEnabled(true);
}
return true;
}
if (evt.target == BtnClose)
{
stop();
BtnConn.enable(true);
BtnClose.enable(false);
LblPrompt.setText("与主机"+hostname+"连接已断开!");
return true;
}
return super.action(evt,obj);
}
public boolean sendFile(String filepathname){
boolean result=true;
if (aftp != null)
{
LblPrompt.setText("正在粘贴文件,请耐心等待....");

String  contentperline;
try{
a="粘贴成功!";
String fg =new  String("\\");
int index = filepathname.lastIndexOf(fg);
String filename = filepathname.substring(index+1);
File localFile ;
localFile = new File(filepathname) ;
RandomAccessFile sendFile = new RandomAccessFile(filepathname,"r");
//
sendFile.seek(0);
outs = aftp.put(filename);
outputs = new DataOutputStream(outs);
while (sendFile.getFilePointer() < sendFile.length() )
{
  ch = sendFile.read();
  outputs.write(ch);
}
outs.close();
sendFile.close();
}
catch(IOException e){
  a = "粘贴失败!";
  result = false ;

}
LblPrompt.setText(a);
showFileContents();
}
else{
result = false;
}
return result;
}

public void showFileContents()
{
StringBuffer buf = new StringBuffer();
lsArea.setText("");
try
{
ins= aftp.list();
while ((ch=ins.read())>=0){
  buf.append((char)ch);
}
    lsArea.appendText(buf.toString());
ins.close();
        }
catch(IOException e)
{
}
}
        public static void main(String args[]){
             Frame f = new Frame("FTP Client");
             f.addWindowListener(new WindowAdapter(){
               public void windowClosing(WindowEvent e){
                   System.exit(0);
               }

             });
             FtpApplet ftp = new  FtpApplet();
             ftp.init();
             ftp.start();
             f.add(ftp);
             f.pack();
             f.setVisible(true);
        }
}