Develop Reference

How to set Java home in JSch to execute a command?

I'm using Jcraft JSch to ssh into a remote machine and execute a command. As it's a non-interactive shell it's not finding Java home. How do I set Java home while using jsch? looking like
((ChannelExec) channel).setEnv("LANG", "UTF-8");
((ChannelExec) channel).setEnv("JAVA_HOME", "/blah/java/J8.0_64/");
is deprecated?
public String sendCommand(String command) {
StringBuilder outputBuffer = new StringBuilder();
try {
Channel channel = sesConnection.openChannel("exec");
((ChannelExec) channel).setEnv("LANG", "UTF-8");
((ChannelExec) channel).setEnv("JAVA_HOME", "/blah/java/J8.0_64/");
((ChannelExec) channel).setCommand(command);
InputStream commandOutput = channel.getInputStream();
channel.connect();
int readByte = commandOutput.read();
while (readByte != 0xffffffff) {
outputBuffer.append((char) readByte);
readByte = commandOutput.read();
}
channel.disconnect();
} catch (IOException ioX) {
logWarning(ioX.getMessage());
return null;
} catch (JSchException jschX) {
logWarning(jschX.getMessage());
return null;
}
return outputBuffer.toString();
}
Error I'm getting while executing a command
JAVA_HOME not set and cannot find javac to deduce location, please set JAVA_HOME.

ChannelExec.setEnv on JSch side probably works. But assuming you are connecting to an OpenSSH server, the server must be explicitly configured to allow you to set the LANG and JAVA_HOME environment variables using the AcceptEnv directive. What it probably is not.
You can try the same using PuTTY (Connection > Data > Environment variables). You will probably get "Server refused to set environment variables" message back.
See also How can I set environment variables when I ssh login to my Unix box by passing custom arguments?
Anyway, the correct solution is to fix your server configuration to set the environment correctly even for non-interactive sessions.
Or as a dirty workaround you can set the variables directly in your command:
JAVA_HOME=/blah/java/J8.0_64/; java ...
See also Certain Unix commands fail with "... not found", when executed through Java using JSch.

This got me when I was trying to run maven using jsch exec.
Easy work-around is to use bash to run your command.
String command = "bash --login -c 'mvn --version'";
((ChannelExec) channel).setCommand(command);
or
((ChannelExec) channel).setCommand("bash --login -c '"+command+"'");

Unable to connect to SFTP server Apache common

I have wrote a java code (using apache common vfs2) to upload files to SFTP server. Recently, I have introduced PGP Security on my server. Now, the java code is not able to connect to this server. Connection with FileZilla is successful. We are using CrushFTP on server and apache-common-vfs2 in java application. Here is the code snippet
String originalFileName = localFile.getName();
manager.init();
FileObject fileToUpload = manager.resolveFile(localFile.getAbsolutePath());
// Create remote file object
FileObject remoteFile = manager.resolveFile(
createConnectionString(originalFileName),
createDefaultFileSystemOptions());
remoteFile.copyFrom(fileToUpload, Selectors.SELECT_SELF);
Methods
public String createConnectionString(String fileName) {
String path = "sftp://" + username + ":" + password + "#" + server +workingDir+"/"+fileName;
logger.info("uploading file at "+path);
return path;
}
public static FileSystemOptions createDefaultFileSystemOptions()
throws FileSystemException {
// Create SFTP options
FileSystemOptions opts = new FileSystemOptions();
// SSH Key checking
SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(opts, "no");
// Root directory set to user home
SftpFileSystemConfigBuilder.getInstance().setUserDirIsRoot(opts, false);
// Timeout is count by Milliseconds
SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, 10000);
return opts;
}
The exception is as follow
Caused by: org.apache.commons.vfs2.FileSystemException: Could not connect to SFTP server at "192.168.13.102".
at org.apache.commons.vfs2.provider.sftp.SftpClientFactory.createConnection(SftpClientFactory.java:170)
at org.apache.commons.vfs2.provider.sftp.SftpFileProvider.doCreateFileSystem(SftpFileProvider.java:97)
... 16 more
Caused by: com.jcraft.jsch.JSchException: Session.connect: java.security.InvalidAlgorithmParameterException: Prime size must be multiple of 64, and can only range from 512 to 1024 (inclusive)
at com.jcraft.jsch.Session.connect(Session.java:565)
Anoney please suggest solution?

The error message indicates you're using a Java release older than 1.8 and Diffie-Hellman parameters larger than 1024 bits. Either update the JDK release to 1.8 or newer, or limit to 1024 bit Diffie-Hellman parameters on the server side (how to do depends on the server software in use, and is server configuration work better asked at Server Fault).

How to provide sftp password through Java

I am using JSCH API to invoke shell commands from java. I am trying to invoke sftp command like this :
Channel channel = (ChannelShell)getSession().openChannel("shell");
channel.connect();
PrintStream out = new PrintStream(channel.getOutputStream());
out.println("#!/bin/bash");
out.println("sftp akumar#sindh");
out.flush();
On Java console i see that it is connecting to this sindh server and then it asks for password.
Connecting to sindh...
akuamr#sindh's password:
How do i provide password to it. I tried
out.println("sftp akumar#sindh");
out.println("password123")
But this dosen't work out. Thanks in advance.

You need to set the password in the Session before connecting:
JSch jsch=new JSch();
Session session = jsch.getSession("akumar", "sindh");
session.setPort(22);
session.setPassword("password123");
session.connect();
ChannelSftp channel = (ChannelSftp) session.openChannel("sftp");
channel.connect();
And then you can use the channel to execute sftp commands.

SFTP: IOException while reading a file with java

I am using com.jcraft.jsch library to read .xls files from an SFTP server. Following is the code to connect to server.
session = jsch.getSession(username, host);
session.setConfig("StrictHostKeyChecking", "no");
session.setPassword(password);
session.connect();
sftpChannel = (ChannelSftp) session.openChannel("sftp");
sftpChannel.connect();
I am using sftpChannel.get(file) to retrieve inputStream to the file. This inputstream is then used to instantiate XSSFWorkbook as shown below:
XSSFWorkbook workbook = new XSSFWorkbook(in);
Problem 1:
When I run the app, it seems to get stuck on the above line for some time (say 5 minutes) and then it throws java.io.IOException: Pipe closed error.
The xls file I am trying to read is 800kb and it works fine when run from local machine.
Problem 2:
The app is designed to process files sequentially. So, if first file fails with IOE, rest of the files also fail as the connection is timed out. To prevent this, I put the below code to check and re-connect:
if(null == session || !session.isConnected()){
log.debug("Session is not connected/timed out. Creating a new session");
openSftpSession();
log.debug("New session is created");
}
//openSftpSession() is the code to create a new session as explained in the beginning of the question.
When this code gets executed, following exception gets thrown:
java.io.IOException: error: 4: RequestQueue: unknown request id 1028332337
at com.jcraft.jsch.ChannelSftp$2.read(ChannelSftp.java:1407)
at java.io.FilterInputStream.read(FilterInputStream.java:133)
at java.io.PushbackInputStream.read(PushbackInputStream.java:186)
//More lines
edit : code to retrieve input stream
public InputStream getInputStream(String folder, String file) throws Exception{
sftpChannel.cd(root + folder);
log.debug("current directory:" + sftpChannel.pwd());
log.debug("File :" + folder + " " + file);
return sftpChannel.get(file);
}
Can anyone please help me get over this? I believe an alternate approach to prevent timeout is to download the file in some temp directory and process. However, I don't really want to do that.
Thanks in advance.

Have you checked to see whether the approach you describe (download into temp file) works? Just to verify that your inputstream is ok.. How long does it take to download into a local file over that connection?
If you don't want to manage a temp file you could always pull it into a byte[] in memory, so long as you don't have to scale to much more than 800kbs.. Use Apache Commons as such:
InputStream in = sftpChannel.get(file);
byte[] inBytes = org.apache.commons.io.IOUtils.toByteArray(in)
ByteArrayInputStream inByteStream = new ByteArrayInputStream(inBytes)
XSSFWorkbook workbook = new XSSFWorkbook(inByteStream);
As for the Request Id, it looks like the old session/channel is still trying to do a read but is no longer able to. Maybe you aren't closing out that session/channel properly. From the openSftpSession() code it looks like you would only be overwriting the references without properly shutting them down.

Java code for connect alfresco through ftps connection

When I try to connect our alfresco through SFTP it is not able to connect alfresco. It hangs the explorer and no error goes in the logger file also.
public void FTPTest()throws SocketException, IOException, NoSuchAlgorithmException
{
FTPSClient ftp = new FTPSClient("SSL");
System.out.println("1");
ftp.connect("172.17.178.144",2121); // or "localhost" in your case
System.out.println("2"+ftp.getReplyString());
System.out.println("login: "+ftp.login("admin", "admin"));
System.out.println("3"+ ftp.getReplyString());
ftp.changeWorkingDirectory("/alfresco");
// list the files of the current directory
FTPFile[] files = ftp.listFiles();
System.out.println("Listed "+files.length+" files.");
for(FTPFile file : files) {
System.out.println(file.getName());
}
// lets pretend there is a JPEG image in the present folder that we want to copy to the desktop (on a windows machine)
ftp.setFileType(FTPClient.BINARY_FILE_TYPE); // don't forget to change to binary mode! or you will have a scrambled image!
FileOutputStream br = new FileOutputStream("C:\\Documents and Settings\\casonkl\\Desktop\\my_downloaded_image_new_name.jpg");
ftp.retrieveFile("name_of_image_on_server.jpg", br);
ftp.disconnect();
}
I got output in our console only
1
at the execution of ftp.connect("172.17.178.144",2121); this code system will be hang no error got in our console
I am able to connect to my Alfresco through SFTP with the Filezila FTP client software. Can any one help me resolve this issue?

If I'm not mistaken then Alfresco chose for FTPS.
So try it with the following code here: http://alvinalexander.com/java/jwarehouse/commons-net-2.2/src/main/java/examples/ftp/FTPSExample.java.shtml