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This article mainly explains the "Java how to achieve FTP server file upload and download", the article explains the content is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "Java how to achieve FTP server file upload and download" bar!

Preface

Due to business requirements, it is necessary to implement the file upload and download functions of ftp server. So I made use of commons-net, a toolkit of apache. It is easy to use, but some details are rather awkward, so I would like to explain.

Use

The core tool class of the third-party package is FTPClient, which needs to be connected and logged in, whether it is file upload or file download, which will be reflected in the code.

Preparatory work

Introduce maven dependency

Commons-net commons-net 3.6

Connection information of the ftp server

Hostnam

Port

User name

Password

If you need to build and configure your own file server, please build your own Baidu

Common commands rm-rf directory name mkdir directory name create directory touch file name new file cd directory name switch directory kill-9 process ID kill process chmod configuration permissions file upload

File upload is actually putting our local files in the directory specified by the file server. Imagine what we would do if we created a new folder and file on a linux server at this time.

Create folder mkdir folder name

Enter the cd folder name in the folder

Create a new file touch file name

In fact, the code used by FTPClient to upload files means the same thing, and the main methods used are:

MakeDirectory (path)

ChangeWorkingDirectory (path)

StoreFile (remoteFilename, inputStream)

Correspond to the above three steps respectively.

The following is the complete code, but there are a few details to explain:

Make sure that the logged-in user has sufficient permissions, such as reading and writing files.

The makeDirectory method cannot create multi-level directories, only one layer at a time.

The failure to create the file may be because the user does not have permissions, or the directory already exists.

The problem of Chinese garbled code. Look at the code.

Public static void main (String [] args) {FTPClient ftpClient = new FTPClient (); try {/ / 1. Connect to login ftpClient.connect ("hostname", port); boolean loginSuccessful = ftpClient.login ("user name", "password!"); System.out.println (loginSuccessful? "login success": "login failed"); String remotePath = "Chinese directory"; / / the directory where the uploaded file resides String remotePathAfterTransferCode = new String (remotePath.getBytes ("utf-8"), "iso-8859-1"); / / prevent Chinese garbled String localFile = "/ Users/zzz/Desktop/ftp-server/perfect.txt"; / / Local files to be uploaded String remoteFilename = "remoteFile.txt" / / the file name of the uploaded ftp server / / 2. Create a folder on ftp server: boolean makeDirSuccessful = ftpClient.makeDirectory (remotePathAfterTransferCode); System.out.println ("was the folder created successfully?" + makeDirSuccessful); / / 3. Change the directory boolean changeWorkingDirectorySuccessful = ftpClient.changeWorkingDirectory (remotePathAfterTransferCode); System.out.println (changeWorkingDirectorySuccessful? "change directory successfully": "failed to change directory"); / / 4. Upload local files to ftp server boolean uploadSuccessful = ftpClient.storeFile (remoteFilename, new FileInputStream (new File (localFile); System.out.println (uploadSuccessful? "upload successful": "upload failed"); / / 5. Log in to ftpClient.logout ();} catch (Exception e) {e.printStackTrace ();}}

File download

File downloading also requires the user to connect and log in before downloading.

The core method is retrieveFile ("server file address", output stream)

The specific code is as follows:

Public static void main (String [] args) {FTPClient ftpClient = new FTPClient (); / / specify the local download directory String localPath = "/ Users/zzz/Desktop/ftp-server"; try {ftpClient.connect ("hostname", 21); boolean loginSuccess = ftpClient.login ("username", "password!"); System.out.println (loginSuccess? "login success": "login failed"); / / File download File localFile = new File (localPath + File.separatorChar + "ttt.txt"); OutputStream os = new FileOutputStream (localFile); boolean downloadSuccessful = ftpClient.retrieveFile ("test.txt", os); os.close (); System.out.println (downloadSuccessful? "download successfully!" : "download failed!") ; ftpClient.logout ();} catch (Exception e) {e.printStackTrace ();}} Summary

FTPClient to achieve file upload and download method is very easy to understand, but some details need to pay attention to (common mentioned earlier), of course, the above code is only demo version, the specific requirements need to be optimized, such as exception handling, how to create multi-level folders and so on, and finally, you need to customize the configuration of FTPClient, such as coding, specific API to check the information.

Thank you for your reading, the above is the content of "Java how to upload and download files on FTP server". After the study of this article, I believe you have a deeper understanding of how to achieve file upload and download on FTP server by Java. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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