如何使用Java将FTP服务器上的文件复制到同一服务器上的目录中？
我正在使用Apache Commons FTP上传文件。上传之前，我想检查服务器上是否已存在该文件，并将其备份到同一服务器上的备份目录中。
public static void uploadWithCommonsFTP(File fileToBeUpload){ FTPClient f = new FTPClient();
FTPFile backupDirectory;
try {
f.connect(server.getServer());
f.login(server.getUsername(), server.getPassword());
FTPFile[] directories = f.listDirectories();
FTPFile[] files = f.listFiles();
for(FTPFile file:directories){
if (!file.getName().equalsIgnoreCase("backup")) {
backupDirectory=file;
} else {
f.makeDirectory("backup");
}
}
for(FTPFile file: files){
if(file.getName().equals(fileToBeUpload.getName())){
//copy file to backupDirectory
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
仍然存在问题，当我备份zip文件时，备份的文件已损坏。
public static void backupUploadWithCommonsFTP(File fileToBeUpload) { FTPClient f = new FTPClient();
boolean backupDirectoryExist = false;
boolean fileToBeUploadExist = false;
FTPFile backupDirectory = null;
try {
f.connect(server.getServer());
f.login(server.getUsername(), server.getPassword());
FTPFile[] directories = f.listDirectories();
// Check for existence of backup directory
for (FTPFile file : directories) {
String filename = file.getName();
if (file.isDirectory() && filename.equalsIgnoreCase("backup")) {
backupDirectory = file;
backupDirectoryExist = true;
break;
}
}
if (!backupDirectoryExist) {
f.makeDirectory("backup");
}
// Check if file already exist on the server
f.changeWorkingDirectory("files");
FTPFile[] files = f.listFiles();
f.changeWorkingDirectory("backup");
String filePathToBeBackup="/home/user/backup/";
String prefix;
String suffix;
String fileNameToBeBackup;
FTPFile fileReadyForBackup = null;
f.setFileType(FTP.BINARY_FILE_TYPE);
f.setFileTransferMode(FTP.BINARY_FILE_TYPE);
for (FTPFile file : files) {
if (file.isFile() && file.getName().equals(fileToBeUpload.getName())) {
prefix = FilenameUtils.getBaseName(file.getName());
suffix = ".".concat(FilenameUtils.getExtension(file.getName()));
fileNameToBeBackup = prefix.concat(Calendar.getInstance().getTime().toString().concat(suffix));
filePathToBeBackup = filePathToBeBackup.concat(fileNameToBeBackup);
fileReadyForBackup = file;
fileToBeUploadExist = true;
break;
}
}
// If file already exist on the server create a backup from it otherwise just upload the file.
if(fileToBeUploadExist){
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
f.retrieveFile(fileReadyForBackup.getName(), outputStream);
InputStream is = new ByteArrayInputStream(outputStream.toByteArray());
if(f.storeUniqueFile(filePathToBeBackup, is)){
JOptionPane.showMessageDialog(null, "Backup succeeded.");
f.changeWorkingDirectory("files");
boolean reply = f.storeFile(fileToBeUpload.getName(), new FileInputStream(fileToBeUpload));
if(reply){
JOptionPane.showMessageDialog(null,"Upload succeeded.");
}else{
JOptionPane.showMessageDialog(null,"Upload failed after backup.");
}
}else{
JOptionPane.showMessageDialog(null,"Backup failed.");
}
}else{
f.changeWorkingDirectory("files");
f.setFileType(FTP.BINARY_FILE_TYPE);
f.enterLocalPassiveMode();
InputStream inputStream = new FileInputStream(fileToBeUpload);
ByteArrayInputStream in = new ByteArrayInputStream(FileUtils.readFileToByteArray(fileToBeUpload));
boolean reply = f.storeFile(fileToBeUpload.getName(), in);
System.out.println("Reply code for storing file to server: " + reply);
if(!f.completePendingCommand()) {
f.logout();
f.disconnect();
System.err.println("File transfer failed.");
System.exit(1);
}
if(reply){
JOptionPane.showMessageDialog(null,"File uploaded successfully without making backup." +
"\nReason: There wasn't any previous version of this file.");
}else{
JOptionPane.showMessageDialog(null,"Upload failed.");
}
}
//Logout and disconnect from server
in.close();
f.logout();
f.disconnect();
} catch (IOException e) {
e.printStackTrace();
}
}
回答：
如果您使用的是apache commons net
FTPClient，则有一种直接方法将文件从一个位置移动到另一位置（如果user具有适当的权限）。
ftpClient.rename(from, to);或者，如果您熟悉ftp commands，可以使用类似
ftpClient.sendCommand(FTPCommand.yourCommand, args);if(FTPReply.isPositiveCompletion(ftpClient.getReplyCode())) {
//command successful;
} else {
//check for reply code, and take appropriate action.
}
如果您使用任何其他客户端，请阅读文档，客户端实现之间不会有太大变化。
上面的方法将文件移动到to目录，即文件from不再在目录中。基本上ftp协议意味着要从服务器中传输文件local <->
remote或从remote <-> other remote服务器中不传输文件。
解决此问题的方法会更简单，将完整文件获取到本地，InputStream然后将其作为备份目录中的新文件写回到服务器。
获取完整的文件，
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();ftpClient.retrieveFile(fileName, outputStream);
InputStream is = new ByteArrayInputStream(outputStream.toByteArray());
现在，将此流存储到备份目录。首先，我们需要将工作目录更改为备份目录。
// assuming backup directory is with in current working directoryftpClient.setFileType(FTP.BINARY_FILE_TYPE);//binary files
ftpClient.changeWorkingDirectory("backup");
//this overwrites the existing file
ftpClient.storeFile(fileName, is);
//if you don't want to overwrite it use storeUniqueFile
希望这对您有帮助。
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