<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="ftp"
    xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>FTP/FTPS Adapters</title>
  <para>
    Spring Integration provides support for file transfer operations via FTP and FTPS.
  </para>
  <section id="ftp-intro">
    <title>Introduction</title>
    <para>
      The File Transfer Protocol (FTP) is a simple network protocol which allows you to transfer files between two computers on the Internet.
    </para>
    <para>
    There are two actors when it comes to FTP communication: <emphasis>client</emphasis> and <emphasis>server</emphasis>. 
    To transfer files with FTP/FTPS, you use a <emphasis>client</emphasis> which initiates a connection to a remote computer 
    that is running an FTP <emphasis>server</emphasis>. After the connection is established, the <emphasis>client</emphasis> can choose 
    to send and/or receive copies of files. 
    </para>
    
     <para>
    Spring Integration supports sending and receiving files over FTP/FTPS by providing three <emphasis>client</emphasis>
    side endpoints: <emphasis>Inbound Channel Adapter</emphasis>, <emphasis>Outbound Channel Adapter</emphasis>, and
    <emphasis>Outbound Gateway</emphasis>. It also provides
    convenient namespace-based configuration options for defining these <emphasis>client</emphasis> components.
    </para>
    <para>
    	To use the <emphasis>FTP</emphasis> namespace, add the following to the header of your XML file:
    	<programlisting language="xml"><![CDATA[xmlns:int-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.xsd"
]]></programlisting>
    </para>
  </section>
  
  
  <section id="ftp-session-factory">
  	<title>FTP Session Factory</title>
  	<para>
  	Before configuring FTP adapters you must configure an <emphasis>FTP Session Factory</emphasis>. You can configure 
  	the <emphasis>FTP Session Factory</emphasis> with a regular bean definition where the implementation class is <classname>org.springframework.integration.ftp.session.DefaultFtpSessionFactory</classname>:
	Below is a basic configuration:
	
	<programlisting language="xml"><![CDATA[<bean id="ftpClientFactory" 
	class="org.springframework.integration.ftp.session.DefaultFtpSessionFactory">
		<property name="host" value="localhost"/>
		<property name="port" value="22"/>
		<property name="username" value="kermit"/>
		<property name="password" value="frog"/>
		<property name="clientMode" value="0"/>
		<property name="fileType" value="2"/>
		<property name="bufferSize" value="100000"/>
</bean>]]></programlisting>
	</para>
	<para>
	For FTPS connections all you need to do is use <classname>org.springframework.integration.ftp.session.DefaultFtpsSessionFactory</classname> instead.
	Below is the complete configuration sample:
	
	<programlisting language="xml"><![CDATA[<bean id="ftpClientFactory" 
	class="org.springframework.integration.ftp.client.DefaultFtpsClientFactory">
		<property name="host" value="localhost"/>
		<property name="port" value="22"/>
		<property name="username" value="oleg"/>
		<property name="password" value="password"/>
		<property name="clientMode" value="1"/>
		<property name="fileType" value="2"/>
		<property name="useClientMode" value="true"/>
		<property name="cipherSuites" value="a,b.c"/>
		<property name="keyManager" ref="keyManager"/>
		<property name="protocol" value="SSL"/>
		<property name="trustManager" ref="trustManager"/>
		<property name="prot" value="P"/>
		<property name="needClientAuth" value="true"/>
		<property name="authValue" value="oleg"/>
		<property name="sessionCreation" value="true"/>
		<property name="protocols" value="SSL, TLS"/>
		<property name="implicit" value="true"/>
</bean>]]></programlisting>
	</para>

	<para>
	Every time an adapter requests a session object from its <interfacename>SessionFactory</interfacename> the session is 
	returned from a session pool maintained by a caching wrapper around the factory. A Session in the session pool might go stale 
	(if it has been disconnected by the server due to inactivity) so the <interfacename>SessionFactory</interfacename> 
	will perform validation to make sure that it never returns a stale session to the adapter. If a stale session was encountered,
	it will be removed from the pool, and a new one will be created.
	<note>
	If you experience connectivity problems and would like to trace Session creation as well as see which Sessions are 
	polled you may enable it by setting the logger to TRACE level (e.g., log4j.category.org.springframework.integration.file=TRACE)
	</note>
	</para>

	<para>
	Now all you need to do is inject these session factories into your adapters. Obviously the protocol (FTP or FTPS) that an adapter will 
	use depends on the type of session factory that has been injected into the adapter.
  	</para>
  	<para>
  	<note>
  	A more practical way to provide values for <emphasis>FTP/FTPS Session Factories</emphasis> is by using Spring's property 
  	placeholder support (See: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/beans.html#beans-factory-placeholderconfigurer).
  	</note>
  </para>
  
  <para>
  	<emphasis>Advanced Configuration</emphasis>
  </para>
  
  <para>
  <classname>DefaultFtpSessionFactory</classname> provides an abstraction over the underlying client API which, in the current release of  
  Spring Integration, is <ulink url="http://commons.apache.org/net/">Apache Commons Net</ulink>. This spares you from the low level configuration details 
  of the <classname>org.apache.commons.net.ftp.FTPClient</classname>. However there are times when access to lower level <classname>FTPClient</classname> details is 
  necessary to achieve more advanced configuration (e.g., setting data timeout, default timeout etc.). For that purpose, <classname>AbstractFtpSessionFactory</classname> 
  (the base class for all FTP Session Factories) exposes hooks, in the form of the two post-processing methods below.
  <programlisting language="java"><![CDATA[/**
	 * Will handle additional initialization after client.connect() method was invoked, 
	 * but before any action on the client has been taken 
	 */
	protected void postProcessClientAfterConnect(T t) throws IOException {
		// NOOP
	}
	/**
	 * Will handle additional initialization before client.connect() method was invoked. 
	 */
	protected void postProcessClientBeforeConnect(T client) throws IOException {
		// NOOP
	}]]></programlisting>
	As you can see, there is no default implementation for these two methods. However, by extending <classname>DefaultFtpSessionFactory</classname> you can override these methods 
	to provide more advanced configuration of the <classname>FTPClient</classname>. For example:
	<programlisting language="java"><![CDATA[public class AdvancedFtpSessionFactory extends DefaultFtpSessionFactory {

  protected void postProcessClientBeforeConnect(FTPClient ftpClient) throws IOException {
     ftpClient.setDataTimeout(5000);
     ftpClient.setDefaultTimeout(5000);
  }
}]]></programlisting>
  </para>
  </section>
  
  <section id="ftp-inbound">
  	<title>FTP Inbound Channel Adapter</title>
  	<para>
  	The <emphasis>FTP Inbound Channel Adapter</emphasis> 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.
  	
  	<programlisting language="xml"><![CDATA[<int-ftp:inbound-channel-adapter id="ftpInbound"
				channel="ftpChannel" 
				session-factory="ftpSessionFactory"
				charset="UTF-8"
				auto-create-local-directory="true"
				delete-remote-files="true"
				filename-pattern="*.txt"
				remote-directory="some/remote/path"
				remote-file-separator="/"
				local-filename-generator-expression="#this.toUpperCase() + '.a'"
				local-directory=".">
			<int:poller fixed-rate="1000"/>
</int-ftp:inbound-channel-adapter>]]></programlisting>

	As you can see from the configuration above you can configure an <emphasis>FTP Inbound Channel Adapter</emphasis> via the <code>inbound-channel-adapter</code> 
	element while also providing values for various attributes such as <code>local-directory</code>, <code>filename-pattern</code> 
	(which is based on simple pattern matching, not regular expressions), and of course the reference to a <code>session-factory</code>.
	</para>
	<para>
	By default the transferred file will carry the same name as the original file. If you want to override this behavior you 
	can set the <code>local-filename-generator-expression</code> attribute which allows you to provide a SpEL Expression to generate 
	the name of the local file. Unlike outbound gateways and adapters where the root object of the SpEL Evaluation Context 
	is a <classname>Message</classname>, this inbound adapter does not yet have the Message at the time of evaluation since
	that's what it ultimately generates with the transferred file as its payload. So, the root object of the SpEL Evaluation Context
	is the original name of the remote file (String).
	</para>
	
  	<para>
	Some times file filtering based on the simple pattern specified via <code>filename-pattern</code> attribute might not be 
	sufficient. If this is the case, you can use the <code>filename-regex</code> attribute to specify a Regular Expression 
	(e.g. <code>filename-regex=".*\.test$"</code>). And of course if you need complete control you can use <code>filter</code> 
	attribute and provide a reference to any custom implementation of the 
	<classname>org.springframework.integration.file.filters.FileListFilter</classname>, a strategy interface for filtering a 
	list of files.
  	</para>
  	<note>
	As of Spring Integration 2.0.2, we have added a 'remote-file-separator' attribute. That allows you to configure a
	file separator character to use if the default '/' is not applicable for your particular environment.
	</note>
  	<para>
  	Please refer to the schema for more details on these attributes. 
  	</para>
  	<para>
  	It is also important to understand that the <emphasis>FTP Inbound Channel Adapter</emphasis> is a <emphasis>Polling Consumer</emphasis> and 
  	therefore you must configure a poller (either via a global default or a local sub-element).
    Once a file has been transferred, a Message with a <classname>java.io.File</classname> as its payload will be generated and sent to the channel 
    identified by the <code>channel</code> attribute.
  	</para>
  	<para>
  		<emphasis>More on File Filtering and Large Files</emphasis>
  	</para>
  	<para>
  	Some times the file that just appeared in the monitored (remote) directory is not complete. Typically such a file 
  	will be written with  temporary extension (e.g., foo.txt.writing) and then renamed after the writing process finished.
  	As a user in most cases you are only interested in files that are complete and would like to filter only files that are complete. 
  	To handle these scenarios you can use the filtering support provided by the <code>filename-pattern</code>, <code>filename-regex</code>
  	and <code>filter</code> attributes. Here is an example that uses a custom Filter implementation.
	
	<programlisting language="xml"><![CDATA[<int-ftp:inbound-channel-adapter 
			channel="ftpChannel" 
			session-factory="ftpSessionFactory"
			filter="customFilter"
			local-directory="file:/my_transfers">
			remote-directory="some/remote/path"
	<int:poller fixed-rate="1000"/>
</int-ftp:inbound-channel-adapter>
	
<bean id="customFilter" class="org.example.CustomFilter"/>
]]></programlisting>
  	</para>
  	<para>
  		<emphasis>Poller configuration notes for the inbound FTP adapter</emphasis>
  	</para>
  	<para>
  	The job of the inbound FTP adapter consists of two tasks:
	<emphasis>1) Communicate with a remote server in order to transfer files from a remote directory to a local directory.</emphasis>
	<emphasis>2) For each transferred file, generate a Message with that file as a payload and send it to the channel identified by the 'channel' attribute.</emphasis>

	That is why they are called 'channel-adapters' rather than just 'adapters'. The main job of such an adapter is to generate a 
	Message to be sent to a Message Channel. Essentially, the second task mentioned above takes precedence in such a way that 
	*IF* your local directory already has one or more files it will first generate Messages from those, and *ONLY* 
	when all local files have been processed, will it initiate the remote communication to retrieve more files.
    </para>
    <para>
	Also, when configuring a trigger on the poller you should pay close attention to the <code>max-messages-per-poll</code> 
	attribute. Its default value is 1 for all <classname>SourcePollingChannelAdapter</classname> instances (including FTP).
	This means that as soon as one file is processed, it will wait for the next execution time as determined by your 
	trigger configuration. If you happened to have one or more files sitting in the <code>local-directory</code>, it would process 
	those files before it would initiate communication with the remote FTP server. And, if the <code>max-messages-per-poll</code> 
	were set to 1 (default), then it would be processing only one file at a time with intervals as defined by your trigger,
	essentially working as <emphasis>one-poll = one-file</emphasis>.
  	</para>
  	<para>
  	For typical file-transfer use cases, you most likely want the opposite behavior: to process all the files you can for each 
  	poll and only then wait for the next poll. If that is the case, set <code>max-messages-per-poll</code> to -1. Then, on
  	each poll, the adapter will attempt to generate as many Messages as it possibly can. In other words, it will process 
  	everything in the local directory, and then it will connect to the remote directory to transfer everything that is available 
  	there to be processed locally. Only then is the poll operation considered complete, and the poller will wait for the next execution time.
	</para>
	<para>
		You can alternatively set the 'max-messages-per-poll' value to a positive value indicating the upward limit of Messages to be created
		from files with each poll. For example, a value of 10 means that on each poll it will attempt to process no more than 10 files.
  	</para>
  </section>
  
  <section id="ftp-outbound">
  	<title>FTP Outbound Channel Adapter</title>
  	
  	<para>
  	The <emphasis>FTP Outbound Channel Adapter</emphasis> relies upon a <classname>MessageHandler</classname> implementation that will connect to the 
  	FTP server and initiate an FTP transfer for every file it receives in the payload of incoming Messages. It also supports several 
  	representations of the <emphasis>File</emphasis> so you are not limited only to java.io.File typed payloads.
    The <emphasis>FTP Outbound Channel Adapter</emphasis> 
  	supports the following payloads: 1) <classname>java.io.File</classname> - the actual file object; 
  	2) <classname>byte[]</classname> - a byte array that represents the file contents; and 3) <classname>java.lang.String</classname> - 
  	text that represents the file contents.
  	
  	<programlisting language="xml"><![CDATA[<int-ftp:outbound-channel-adapter id="ftpOutbound"
				channel="ftpChannel" 
				session-factory="ftpSessionFactory"
				charset="UTF-8"
				remote-file-separator="/"
				auto-create-directory="true"
				remote-directory-expression="headers.['remote_dir']"
				temporary-remote-directory-expression="headers.['temp_remote_dir']"
				filename-generator="fileNameGenerator"/>]]></programlisting>	

	As you can see from the configuration above you can configure an <emphasis>FTP Outbound Channel Adapter</emphasis> via the
	<code>outbound-channel-adapter</code> element while also providing values for various attributes such as <code>filename-generator</code> 
	(an implementation of the <classname>org.springframework.integration.file.FileNameGenerator</classname> strategy interface),
	a reference to a <code>session-factory</code>, as well as other attributes. You can also see
	some examples of <code>*expression</code> attributes which allow you to use SpEL 
	to configure things like <code>remote-directory-expression</code>, <code>temporary-remote-directory-expression</code> and <code>remote-filename-generator-expression</code> 
	(a SpEL alternative to <code>filename-generator</code> shown above). As with any component that allows the usage of SpEL, access to Payload and Message Headers is available via 
	'payload' and 'headers' variables.
	Please refer to the schema for more details on
    the available attributes.
	 <note>
	 By default Spring Integration will use <classname>org.springframework.integration.file.DefaultFileNameGenerator</classname> if none is specified.
	 <classname>DefaultFileNameGenerator</classname> will determine the file name based on the value of the <code>file_name</code> header (if it exists)
     in the MessageHeaders, or if the payload of the Message is already a <classname>java.io.File</classname>, then it will use the original name of that file.
	 </note>
  	</para>
  	
  	<para>
  	<important>
  	Defining certain values (e.g., remote-directory) might be platform/ftp server dependent. For example as it 
  	was reported on this forum http://forum.springsource.org/showthread.php?p=333478&amp;posted=1#post333478 on some 
  	platforms you must add slash to the end of the directory definition (e.g., remote-directory="/foo/bar/" 
  	instead of remote-directory="/foo/bar")
  	</important>
  	</para>
 
  </section>
  <section id="ftp-outbound-gateway">
	<title>FTP Outbound Gateway</title>

	<para>
	  The <emphasis>FTP Outbound Gateway</emphasis> provides a limited set of commands to interact with a remote FTP/FTPS server.
	  <para>
	    Commands supported are:
	    <itemizedlist>
		  <listitem>ls (list files)</listitem>
		  <listitem>get (retrieve file)</listitem>
		  <listitem>mget (retrieve file(s))</listitem>
		  <listitem>rm (remove file(s))</listitem>
	    </itemizedlist>
	  </para>
	  <para><emphasis>ls</emphasis></para>
	  <para>
	    ls lists remote file(s) and supports the following options:
	    <itemizedlist>
		  <listitem>-1 - just retrieve a list of filenames, default is to retrieve a
		    list of <classname>FileInfo</classname> objects.</listitem>
		  <listitem>-a - include all files (including those starting with '.')</listitem>
		  <listitem>-f - do not sort the list</listitem>
		  <listitem>-dirs - include directories (excluded by default)</listitem>
		  <listitem>-links - include symbolic links (excluded by default)</listitem>
	    </itemizedlist>
	  </para>
	  <para>
	    In addition, filename filtering is provided, in the same manner as the
	    <classname>inbound-channel-adapter</classname>.
	  </para>
	  <para>
	    The message payload resulting from an <emphasis>ls</emphasis> operation is a list of file names,
	    or a list of <classname>FileInfo</classname> objects. These objects provide
	    information such as modified time, permissions etc.
	  </para>
	  <para>
	    The remote directory that the <emphasis>ls</emphasis> command acted on is provided
	    in the <classname>file_remoteDirectory</classname> header.
	  </para>
	  <para><emphasis>get</emphasis></para>
	  <para>
	    <emphasis>get</emphasis> retrieves a remote file and supports the following option:
	    <itemizedlist>
		  <listitem>-P - preserve the timestamp of the remote file</listitem>
	    </itemizedlist>
	  </para>
	  <para>
		The message payload resulting from a <emphasis>get</emphasis> operation is a
		<classname>File</classname>	object representing the retrieved file.
	  </para>
	  <para>
	    The remote directory is provided in the <classname>file_remoteDirectory</classname> header, and the filename is
	    provided in the <classname>file_remoteFile</classname> header.
	  </para>
	  <para><emphasis>mget</emphasis></para>
	  <para>
	    <emphasis>mget</emphasis> retrieves multiple remote files based on a pattern and supports the following option:
	    <itemizedlist>
		  <listitem>-x - Throw an exception if no files match the pattern (otherwise an empty
		  list is returned)</listitem>
	    </itemizedlist>
	  </para>
	  <para>
		The message payload resulting from an <emphasis>mget</emphasis> operation is a
		<classname>List&lt;File&gt;</classname>	object - a List of File objects, each representing
		a retrieved file.
	  </para>
	  <para>
	    The remote directory is provided in the <classname>file_remoteDirectory</classname> header, and the pattern
	    for the filenames is
	    provided in the <classname>file_remoteFile</classname> header.
	  </para>
	  <para><emphasis>rm</emphasis></para>
	  <para>
	    The <emphasis>rm</emphasis> command has no options.
	  </para>
	  <para>
		The message payload resulting from an <emphasis>rm</emphasis> operation is Boolean.TRUE if the
		remove was successful, Boolean.FALSE otherwise.
	    The remote directory is provided in the <classname>file_remoteDirectory</classname> header, and the filename is
	    provided in the <classname>file_remoteFile</classname> header.
	  </para>
	  <para>
	    In each case, the PATH that these commands act on is provided by the 'expression'
	    property of the gateway. For the mget command, the expression might evaluate to '*', meaning
	    retrieve all files, or 'somedirectory/*' etc.
	  </para>
	</para>
	<para>
	  Here is an example of a gateway configured for an ls command...
	  <programlisting language="xml"><![CDATA[<int-ftp:outbound-gateway id="gateway1"
		session-factory="ftpSessionFactory"
		request-channel="inbound1"
		command="ls"
		command-options="-1"
		expression="payload"
		reply-channel="toSplitter"/>
]]></programlisting>
	</para>
	<para>
	  The payload of the message sent to the toSplitter channel is a list of String objects
	  containing the filename of each file. If the <classname>command-options</classname> was
	  omitted, it would be a list of <classname>FileInfo</classname> objects. Options are
	  provided space-delimited, e.g. <classname>command-options="-1 -dirs -links"</classname>.
	</para>
  </section>
  <section id="ftp-session-caching">
	<title>FTP Session Caching</title>
	<para>
		As of version 2.1 we've exposed more flexibility with regard to session management for remote file adapters (e.g., FTP, SFTP etc).
	    In previous versions the sessions were cached automatically by default. We did expose a <code>cache-sessions</code> attribute for
	    disabling the auto caching, but that solution did not provide a way to configure other session caching attributes. For example, one
	    of the requested features was to support a limit on the number of sessions created since a remote server may impose a limit on the
	    number of client connections. To support that requirement and other configuration options, we decided to promote explicit definition
	    of the <classname>CachingSessionFactory</classname> instance. That provides the <code>sessionCacheSize</code> and <code>sessionWaitTimeout</code>
	    properties. As its name suggests, the  <code>sessionCacheSize</code> property controls how many active sessions this adapter will
	    maintain in its cache (the DEFAULT is unbounded). If the <code>sessionCacheSize</code> threshold has been reached, any attempt to
	    acquire another session will block until either one of the cached sessions becomes available or until the wait time for a Session 
	    expires (the DEFAULT wait time is Integer.MAX_VALUE). The <code>sessionWaitTimeout</code> property enables configuration of that value.
    </para>
    <para>
    If you want your Sessions to be cached, simply configure your default Session Factory as described above and then
    wrap it in an instance of <classname>CachingSessionFactory</classname> where you may provide those additional properties.

    <programlisting language="xml"><![CDATA[<bean id="ftpSessionFactory" class="org.springframework.integration.ftp.session.DefaultFtpSessionFactory">
		<property name="host" value="localhost"/>
	</bean>
	
	<bean id="cachingSessionFactory" class="org.springframework.integration.file.remote.session.CachingSessionFactory">
		<constructor-arg ref="ftpSessionFactory"/>
		<constructor-arg value="10"/>
		<property name="sessionWaitTimeout" value="1000"/>
	</bean>]]></programlisting>
	
	In the above example you see a <classname>CachingSessionFactory</classname> created with the
	<code>sessionCacheSize</code> set to 10 and the <code>sessionWaitTimeout</code> set to 1 second (its value is in millliseconds).

	</para>
  </section>
</chapter>
