在創建JSCH中的新目錄之前，如何檢查目錄是否存在

Question

如何在使用JSCH SFTP API創建新目錄之前檢查目錄是否存在？我正在嘗試使用lstat，但不確定它是否在執行我需要的工作。提前感謝

Answer 1

在這種情況下，最好只創建並處理錯誤。這種方式的操作是原子的，在SSH的情況下，您還可以節省大量的網絡流量。如果您先進行測試，那麼會出現一個時間窗口，在此期間情況可能會發生變化，您必須處理錯誤結果。

Answer 2

這是我如何檢查JSch中的目錄存在。

創建目錄，如果目錄不存在ONT

ChannelSftp channelSftp = (ChannelSftp)channel; 
String currentDirectory=channelSftp.pwd(); 
String dir="abc"; 
SftpATTRS attrs=null; 
try { 
    attrs = channelSftp.stat(currentDirectory+"/"+dir); 
} catch (Exception e) { 
    System.out.println(currentDirectory+"/"+dir+" not found"); 
} 

if (attrs != null) { 
    System.out.println("Directory exists IsDir="+attrs.isDir()); 
} else { 
    System.out.println("Creating dir "+dir); 
    channelSftp.mkdir(dir); 
} 

Answer 3

我在這裏重複了同樣的答案在更廣的範圍內。檢查目錄是否存在並創建新目錄的特定行是

  SftpATTRS attrs; 
      try { 
       attrs = channel.stat(localChildFile.getName()); 
      }catch (Exception e) { 
       channel.mkdir(localChildFile.getName()); 
      } 

注意。 localChildFile.getName()是您要檢查的目錄名稱。下面附加了整個類，遞歸地將目錄的文件或內容發送到遠程服務器。

import com.jcraft.jsch.*; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 

import java.io.*; 

/** 
* Created by krishna on 29/03/2016. 
*/ 
public class SftpLoader { 
private static Logger log = LoggerFactory.getLogger(SftpLoader.class.getName()); 

ChannelSftp channel; 
String host; 
int port; 
String userName ; 
String password ; 
String privateKey ; 


public SftpLoader(String host, int port, String userName, String password, String privateKey) throws JSchException { 
    this.host = host; 
    this.port = port; 
    this.userName = userName; 
    this.password = password; 
    this.privateKey = privateKey; 
    channel = connect(); 
} 

private ChannelSftp connect() throws JSchException { 
    log.trace("connecting ..."); 

    JSch jsch = new JSch(); 
    Session session = jsch.getSession(userName,host,port); 
    session.setPassword(password); 
    jsch.addIdentity(privateKey); 
    java.util.Properties config = new java.util.Properties(); 
    config.put("StrictHostKeyChecking", "no"); 
    session.setConfig(config); 
    session.connect(); 
    Channel channel = session.openChannel("sftp"); 
    channel.connect(); 
    log.trace("connected !!!"); 
    return (ChannelSftp)channel; 
} 

public void transferDirToRemote(String localDir, String remoteDir) throws SftpException, FileNotFoundException { 
    log.trace("local dir: " + localDir + ", remote dir: " + remoteDir); 

    File localFile = new File(localDir); 
    channel.cd(remoteDir); 

    // for each file in local dir 
    for (File localChildFile: localFile.listFiles()) { 

     // if file is not dir copy file 
     if (localChildFile.isFile()) { 
      log.trace("file : " + localChildFile.getName()); 
      transferFileToRemote(localChildFile.getAbsolutePath(),remoteDir); 

     } // if file is dir 
     else if(localChildFile.isDirectory()) { 

      // mkdir the remote 
      SftpATTRS attrs; 
      try { 
       attrs = channel.stat(localChildFile.getName()); 
      }catch (Exception e) { 
       channel.mkdir(localChildFile.getName()); 
      } 

      log.trace("dir: " + localChildFile.getName()); 

      // repeat (recursive) 
      transferDirToRemote(localChildFile.getAbsolutePath(), remoteDir + "/" + localChildFile.getName()); 
      channel.cd(".."); 
     } 
    } 

} 

public void transferFileToRemote(String localFile, String remoteDir) throws SftpException, FileNotFoundException { 
    channel.cd(remoteDir); 
    channel.put(new FileInputStream(new File(localFile)), new File(localFile).getName(), ChannelSftp.OVERWRITE); 
} 


public void transferToLocal(String remoteDir, String remoteFile, String localDir) throws SftpException, IOException { 
    channel.cd(remoteDir); 
    byte[] buffer = new byte[1024]; 
    BufferedInputStream bis = new BufferedInputStream(channel.get(remoteFile)); 

    File newFile = new File(localDir); 
    OutputStream os = new FileOutputStream(newFile); 
    BufferedOutputStream bos = new BufferedOutputStream(os); 

    log.trace("writing files ..."); 
    int readCount; 
    while((readCount = bis.read(buffer)) > 0) { 
     bos.write(buffer, 0, readCount); 
    } 
    log.trace("completed !!!"); 
    bis.close(); 
    bos.close(); 
}