I took miku's answer and jsch example code. I then had to download multiple files during the session and preserve original timestamps. This is my example code how to do it, probably many people find it usefull. Please ignore filenameHack() function its my own usecase.
package examples;
import com.jcraft.jsch.*;
import java.io.*;
import java.util.*;
public class ScpFrom2 {
public static void main(String[] args) throws Exception {
Map params = parseParams(args);
if (params.isEmpty()) {
System.err.println("usage: java ScpFrom2 "
+ " user=myid password=mypwd"
+ " host=myhost.com port=22"
+ " encoding="
+ " \"remotefile1=/some/file.png\""
+ " \"localfile1=file.png\""
+ " \"remotefile2=/other/file.txt\""
+ " \"localfile2=file.txt\""
);
return;
}
// default values
if (params.get("port") == null)
params.put("port", "22");
if (params.get("encoding") == null)
params.put("encoding", "ISO-8859-1"); //"UTF-8"
Session session = null;
try {
JSch jsch=new JSch();
session=jsch.getSession(
params.get("user"), // myuserid
params.get("host"), // my.server.com
Integer.parseInt(params.get("port")) // 22
);
session.setPassword( params.get("password") );
session.setConfig("StrictHostKeyChecking", "no"); // do not prompt for server signature
session.connect();
// this is exec command and string reply encoding
String encoding = params.get("encoding");
int fileIdx=0;
while(true) {
fileIdx++;
String remoteFile = params.get("remotefile"+fileIdx);
String localFile = params.get("localfile"+fileIdx);
if (remoteFile == null || remoteFile.equals("")
|| localFile == null || localFile.equals("") )
break;
remoteFile = filenameHack(remoteFile);
localFile = filenameHack(localFile);
try {
downloadFile(session, remoteFile, localFile, encoding);
} catch (Exception ex) {
ex.printStackTrace();
}
}
} catch(Exception ex) {
ex.printStackTrace();
} finally {
try{ session.disconnect(); } catch(Exception ex){}
}
}
private static void downloadFile(Session session,
String remoteFile, String localFile, String encoding) throws Exception {
// send exec command: scp -p -f "/some/file.png"
// -p = read file timestamps
// -f = From remote to local
String command = String.format("scp -p -f \"%s\"", remoteFile);
System.console().printf("send command: %s%n", command);
Channel channel=session.openChannel("exec");
((ChannelExec)channel).setCommand(command.getBytes(encoding));
// get I/O streams for remote scp
byte[] buf=new byte[32*1024];
OutputStream out=channel.getOutputStream();
InputStream in=channel.getInputStream();
channel.connect();
buf[0]=0; out.write(buf, 0, 1); out.flush(); // send '\0'
// reply: T 0 0\n
// times are in seconds, since 1970-01-01 00:00:00 UTC
int c=checkAck(in);
if(c!='T')
throw new IOException("Invalid timestamp reply from server");
long tsModified = -1; // millis
for(int idx=0; ; idx++){
in.read(buf, idx, 1);
if(tsModified < 0 && buf[idx]==' ') {
tsModified = Long.parseLong(new String(buf, 0, idx))*1000;
} else if(buf[idx]=='\n') {
break;
}
}
buf[0]=0; out.write(buf, 0, 1); out.flush(); // send '\0'
// reply: C0644 \n
// length is given as a text "621873" bytes
c=checkAck(in);
if(c!='C')
throw new IOException("Invalid filename reply from server");
in.read(buf, 0, 5); // read '0644 ' bytes
long filesize=-1;
for(int idx=0; ; idx++){
in.read(buf, idx, 1);
if(buf[idx]==' ') {
filesize = Long.parseLong(new String(buf, 0, idx));
break;
}
}
// read remote filename
String origFilename=null;
for(int idx=0; ; idx++){
in.read(buf, idx, 1);
if(buf[idx]=='\n') {
origFilename=new String(buf, 0, idx, encoding); // UTF-8, ISO-8859-1
break;
}
}
System.console().printf("size=%d, modified=%d, filename=%s%n"
, filesize, tsModified, origFilename);
buf[0]=0; out.write(buf, 0, 1); out.flush(); // send '\0'
// read binary data, write to local file
FileOutputStream fos = null;
try {
File file = new File(localFile);
fos = new FileOutputStream(file);
while(filesize > 0) {
int read = Math.min(buf.length, (int)filesize);
read=in.read(buf, 0, read);
if(read < 0)
throw new IOException("Reading data failed");
fos.write(buf, 0, read);
filesize -= read;
}
fos.close(); // we must close file before updating timestamp
fos = null;
if (tsModified > 0)
file.setLastModified(tsModified);
} finally {
try{ if (fos!=null) fos.close(); } catch(Exception ex){}
}
if(checkAck(in) != 0)
return;
buf[0]=0; out.write(buf, 0, 1); out.flush(); // send '\0'
System.out.println("Binary data read");
}
private static int checkAck(InputStream in) throws IOException {
// b may be 0 for success
// 1 for error,
// 2 for fatal error,
// -1
int b=in.read();
if(b==0) return b;
else if(b==-1) return b;
if(b==1 || b==2) {
StringBuilder sb=new StringBuilder();
int c;
do {
c=in.read();
sb.append((char)c);
} while(c!='\n');
throw new IOException(sb.toString());
}
return b;
}
/**
* Parse key=value pairs to hashmap.
* @param args
* @return
*/
private static Map parseParams(String[] args) throws Exception {
Map params = new HashMap();
for(String keyval : args) {
int idx = keyval.indexOf('=');
params.put(
keyval.substring(0, idx),
keyval.substring(idx+1)
);
}
return params;
}
private static String filenameHack(String filename) {
// It's difficult reliably pass unicode input parameters
// from Java dos command line.
// This dirty hack is my very own test use case.
if (filename.contains("${filename1}"))
filename = filename.replace("${filename1}", "Korilla ABC ÅÄÖ.txt");
else if (filename.contains("${filename2}"))
filename = filename.replace("${filename2}", "test2 ABC ÅÄÖ.txt");
return filename;
}
}
