JAVA写文件到FTP的两种方法

1.使用URL：

URL url = new URL( " ftp://javaa:javaa@172.168.2.222:21/test/javaa.txt " );
PrintWriter pw = new PrintWriter(url.openConnection().getOutputStream());
pw.write( " this is a test " );
pw.flush();
pw.close();
上面是代码的片断,其中URL构造函数的参数可以用不同的访问协议(比如http,ftp等),"//"后跟着的是用户名和密码,两者用":"隔开,紧跟着是分隔符"@","@"以后的是IP地址和端口,然后是目录,最后才是我们要写入的文件名,其中目录是必须存在的,否则会抛出 FileNotFoundException,文件可以是不存在的,不存在的时候就会新建文件,否则就会用新的内容覆盖以前的内容;

2.使用FtpClient：

FtpClient ftpClient = new FtpClient();
ftpClient.openServer( " 172.168.2.222 " , 21 ); // IP地址和端口
ftpClient.login( " javaa " , " javaa " ); // 用户名和密码，匿名登陆的话用户名为anonymous,密码为非空字符串
ftpClient.cd( " test " ); // 切换到test目录
PrintWriter pw = new PrintWriter(ftpClient.put( " javaa.txt " )); // 写入的文件名
pw.write( " this is a test " );
pw.flush();
pw.close();

3.用PASV模式传送数据的FtpClient
import sun.net.ftp.FtpClient;
import java.net.Socket;
import java.io.IOException;

public class PasvFtpClient
extends FtpClient{

/**
* FTP服务器的地址
*/
private String serverAddr;
/**
* 连接到FTP服务器的Socket
*/
private Socket socket;
/**
* 仿造父类定义的静态变量
*/
protected final static int FTP_ERROR=3;
/**
* 仿造父类定义的静态变量
*/
protected final static int FTP_SUCCESS=1;

public PasvFtpClient(String s) throws IOException{
super(s);
serverAddr=s;
socket=null;
}

public PasvFtpClient(String s,int i) throws IOException{
super(s,i);
serverAddr=s;
socket=null;
}

public PasvFtpClient(){
super();
socket=null;
}

/**
* 复写的主要部分，父类采用PORT模式，这里改为PASV模式
* @param s 传入的FTP命令
* @return 连接到FTP服务器的Socket
* @throws IOException
*/
protected Socket openDataConnection(String s) throws IOException{
if (socket==null){
String s1="PASV";
if (issueCommand(s1)==FTP_ERROR){
MyFtpProtocolException ftpprotocolexception=new MyFtpProtocolException(
"PASV");
throw ftpprotocolexception;
}
String responseStr=this.getResponseString();
int location=responseStr.lastIndexOf(",");
int n=Integer.parseInt(responseStr.substring(location+1,
responseStr.indexOf(")")));
responseStr=responseStr.substring(0,location);
location=responseStr.lastIndexOf(",");
int m=Integer.parseInt(responseStr.substring(location+1,
responseStr.length()));
socket=new Socket(serverAddr,m*256+n);
}
if (issueCommand(s)==FTP_ERROR){
MyFtpProtocolException ftpprotocolexception1=new MyFtpProtocolException(s);
throw ftpprotocolexception1;
}
return socket;
}

/**
* 关闭与FTP服务器的连接
* @throws IOException
*/
public void closeServer() throws IOException{
socket.close();
socket=null;
super.closeServer();
}

/**
* 打开与FTP服务器的连接
* @param s FTP服务器地址
* @param i FTP服务器端口
* @throws IOException
*/
public void openServer(String s,int i) throws IOException{
super.openServer(s,i);
serverAddr=s;
}
}

/**
* 自定义的FTP异常类
*/
class MyFtpProtocolException
extends IOException{
MyFtpProtocolException(String s){
super(s);
}
}