File Transfer Protocol (FTP) is a simple network protocol which allows you to transfer files between two computers on the Internet.

There are two actors when it comes to FTP communication - client and server. To transfer files with FTP/FTPS, you use client which initiates a connection to a remote computer running an FTP server software. After the connection is established, the client can choose to send and/or receive copies of files.

Spring Integration supports sending and receiving files over FTP/FTPS by providing two types of clients - Inbound Channel Adapters and Outbound Channel Adapters as well as convenient namespace configuration to define these clients.

FTP

xmlns:ftp="http://www.springframework.org/schema/integration/ftp"
xsi:schemaLocation="http://www.springframework.org/schema/integration/ftp 
	http://www.springframework.org/schema/integration/ftp/spring-integration-ftp-2.0.xsd" 

FTPS

xmlns:ftps="http://www.springframework.org/schema/integration/ftps"
xsi:schemaLocation="http://www.springframework.org/schema/integration/ftps 
	http://www.springframework.org/schema/integration/ftp/spring-integration-ftps-2.0.xsd" 

FTP Inbound Channel Adapter is a special listener that will connect to the FTP server and will listen for the remote directory events (e.g., new file created) at which point it will initiate a file transfer.

<ftp:inbound-channel-adapter 
		remote-directory="/foo/bar/ftp/files" 
		channel="ftpIn" 
		host="localhost" 
		auto-delete-remote-files-on-sync="false"
		username="user" 
		password="password" 
		port="21"	 
		filename-pattern=".*?txt">
	<int:poller fixed-rate="1000"/>
</ftp:inbound-channel-adapter>

As you can see form the configuration above you can configure FTP Inbound Channel Adapter via inbound-channel-adapter element while also providing values for various attributes such as username and password to connect to an FTP server, as well as other attributes. Please refer to the schema for more details on these attributes.

It is also important to understand that FTP Inbound Channel Adapter is a polling consumer and therefore you must configure a poller (global or local). Once the file has been transferred a Message with java.io.File being a payload will be generated and sent to the channel identified with channel attribute.

FTPS Inbound Channel Adapter adds support for secured file receive operations with FTP servers that support Transport Layer Security (TLS). Configuration of the adapter itself is very similar to the FTP Inbound Channel Adapter and is use the same inbound-channel-adapter element but from the FTPS namespace.

<ftps:inbound-channel-adapter 
		remote-directory="/foo/bar/ftp/files" 
		channel="ftpIn" 
		host="localhost" 
		auto-delete-remote-files-on-sync="false"
		username="user" 
		password="password" 
		port="2222"	 
		filename-pattern=".*?txt">
	<int:poller fixed-rate="1000"/>
</ftps:inbound-channel-adapter>

FTP Outbound Channel Adapter is a special MessageHandler that will connect to the FTP server and will initiate an FTP transfer for every file it will receive in the payload of the Message. It also supports several representation of the File so you are not limited only to the File object. FTP Outbound Channel Adapter supports the following payloads: 1) java.io.File - the actual file object; 2) byte[] - byte array that represents the file contents; 3) java.lang.String - represents the file path.

<ftp:outbound-channel-adapter
			remote-directory="${ftp.remotedir}"
			channel="ftpOutbound"
			host="${ftp.host}"
			file-type="binary-file-type"
			username="${ftp.username}"
			password="${ftp.password}" 
			port="2222"
			client-mode="passive-local-data-connection-mode"/>

As you can see form the configuration above you can configure FTP Outbound Channel Adapter via outbound-channel-adapter element while also providing values for various attributes such as username and password to connect to an FTP server, as well as other attributes. Please refer to the schema for more details on these attributes.

FTPS Outbound Channel Adapter adds support for secured file send operations with FTP servers that support Transport Layer Security (TLS). Configuration of the adapter itself is very similar to the FTP Outbound Channel Adapter and is use the same outbound-channel-adapter element but from the FTPS namespace: