Java实现ftp功能源代码：
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);
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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....");
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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);
}
}
