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FTP Outbound Gateway

The FTP outbound gateway provides a limited set of commands to interact with a remote FTP or FTPS server. The supported commands are:

  • ls (list files)

  • nlst (list file names)

  • get (retrieve file)

  • mget (retrieve file(s))

  • rm (remove file(s))

  • mv (move/rename file)

  • put (send file)

  • mput (send multiple files)

Using the ls Command

ls lists remote files and supports the following options:

  • -1: Retrieve a list of file names. The default is to retrieve a list of FileInfo objects.

  • -a: Include all files (including those starting with '.')

  • -f: Do not sort the list

  • -dirs: Include directories (they are excluded by default)

  • -links: Include symbolic links (they are excluded by default)

  • -R: List the remote directory recursively

In addition, filename filtering is provided, in the same manner as the inbound-channel-adapter. See FTP Inbound Channel Adapter.

The message payload resulting from an ls operation is a list of file names or a list of FileInfo objects. These objects provide information such as modified time, permissions, and other details.

The remote directory that the ls command acted on is provided in the file_remoteDirectory header.

When using the recursive option (-R), the fileName includes any subdirectory elements, representing a relative path to the file (relative to the remote directory). If the -dirs option is included, each recursive directory is also returned as an element in the list. In this case, it is recommended that you not use the -1 option, because you would not be able to distinguish files from directories, which you can do with the FileInfo objects.

Starting with version 4.3, the FtpSession supports null for the list() and listNames() methods. Therefore, you can omit the expression attribute. For convenience, Java configuration has two constructors that do not have an expression argument. or LS, NLST, PUT and MPUT commands, null is treated as the client working directory, according to the FTP protocol. All other commands must be supplied with the expression to evaluate the remote path against the request message. You can set the working directory with the FTPClient.changeWorkingDirectory() function when you extend the DefaultFtpSessionFactory and implement the postProcessClientAfterConnect() callback.

Using the nlst Command

Version 5 introduced support for the nlst command.

nlst lists remote file names and supports only one option:

  • -f: Do not sort the list

The message payload resulting from an nlst operation is a list of file names.

The remote directory that the nlst command acted on is provided in the file_remoteDirectory header.

Unlike the -1 option for the ls command, which uses the LIST command, the nlst command sends an NLST command to the target FTP server. This command is useful when the server does not support LIST (due to security restrictions, for example). The result of the nlst operation is the names without other detail. Therefore, the framework cannot determine if an entity is a directory, to perform filtering or recursive listing, for example.

Using the get Command

get retrieves a remote file. It supports the following option:

  • -P: Preserve the timestamp of the remote file.

  • -stream: Retrieve the remote file as a stream.

  • -D: Delete the remote file after successful transfer. The remote file is not deleted if the transfer is ignored, because the FileExistsMode is IGNORE and the local file already exists.

The file_remoteDirectory header provides the remote directory name, and the file_remoteFile header provides the file name.

The message payload resulting from a get operation is a File object that represents the retrieved file or an InputStream when you use the -stream option. The -stream option allows retrieving the file as a stream. For text files, a common use case is to combine this operation with a file splitter or a stream transformer. When consuming remote files as streams, you are responsible for closing the Session after the stream is consumed. For convenience, the Session is provided in the closeableResource header, which you can access with a convenience method on IntegrationMessageHeaderAccessor The following example shows how to use the convenience method:

Closeable closeable = new IntegrationMessageHeaderAccessor(message).getCloseableResource();
if (closeable != null) {
    closeable.close();
}

Framework components such as the file splitter and the stream transformer automatically close the session after the data is transferred.

The following example shows how to consume a file as a stream:

<int-ftp:outbound-gateway session-factory="ftpSessionFactory"
                            request-channel="inboundGetStream"
                            command="get"
                            command-options="-stream"
                            expression="payload"
                            remote-directory="ftpTarget"
                            reply-channel="stream" />

<int-file:splitter input-channel="stream" output-channel="lines" />
If you consume the input stream in a custom component, you must close the Session. You can do so either in your custom code or by routing a copy of the message to a service-activator and using SpEL, as the following example shows: 
<int:service-activator input-channel="closeSession"
    expression="headers['closeableResource'].close()" />

Using the mget Command

mget retrieves multiple remote files based on a pattern and supports the following options:

  • -P: Preserve the timestamps of the remote files.

  • -R: Retrieve the entire directory tree recursively.

  • -x: Throw an exception if no files match the pattern (otherwise an empty list is returned).

  • -D: Delete each remote file after successful transfer. The remote file is not deleted if the transfer is ignored, because the FileExistsMode is IGNORE and the local file already exists.

The message payload resulting from an mget operation is a List<File> object (that is, a List of File objects, each representing a retrieved file).

Starting with version 5.0, if the FileExistsMode is IGNORE, the payload of the output message no longer contains files that were not fetched due to the file already existing. Previously, the list contained all files, including those that already existed.

The expression used to determine the remote path should produce a result that ends with - e.g. somedir/ will fetch the complete tree under somedir.

Starting with version 5.0, a recursive mget, combined with the new FileExistsMode.REPLACE_IF_MODIFIED mode, can be used to periodically synchronize an entire remote directory tree locally. This mode replaces the local file’s last modified timestamp with the remote timestamp, regardless of the -P (preserve timestamp) option.

Using recursion (-R)

The pattern is ignored, and * is assumed. By default, the entire remote tree is retrieved. However, files in the tree can be filtered, by providing a FileListFilter. Directories in the tree can also be filtered this way. A FileListFilter can be provided by reference, by filename-pattern, or by filename-regex attributes. For example, filename-regex="(subDir|.*1.txt)" retrieves all files ending with 1.txt in the remote directory and the subDir child directory. However, the next example shows an alternative, which version 5.0 made available.

If a subdirectory is filtered, no additional traversal of that subdirectory is performed.

The -dirs option is not allowed (the recursive mget uses the recursive ls to obtain the directory tree, so the directories themselves cannot be included in the list).

Typically, you would use the #remoteDirectory variable in the local-directory-expression so that the remote directory structure is retained locally.

The persistent file list filters now have a boolean property forRecursion. Setting this property to true, also sets alwaysAcceptDirectories, which means that the recursive operation on the outbound gateways (ls and mget) will now always traverse the full directory tree each time. This is to solve a problem where changes deep in the directory tree were not detected. In addition, forRecursion=true causes the full path to files to be used as the metadata store keys; this solves a problem where the filter did not work properly if a file with the same name appears multiple times in different directories. IMPORTANT: This means that existing keys in a persistent metadata store will not be found for files beneath the top level directory. For this reason, the property is false by default; this may change in a future release.

Starting with version 5.0, the FtpSimplePatternFileListFilter and FtpRegexPatternFileListFilter can be configured to always pass directories by setting the alwaysAcceptDirectories property to true. Doing so allows recursion for a simple pattern, as the following examples show:

<bean id="starDotTxtFilter"
        class="org.springframework.integration.ftp.filters.FtpSimplePatternFileListFilter">
    <constructor-arg value="*.txt" />
    <property name="alwaysAcceptDirectories" value="true" />
</bean>

<bean id="dotStarDotTxtFilter"
            class="org.springframework.integration.ftp.filters.FtpRegexPatternFileListFilter">
    <constructor-arg value="^.*\.txt$" />
    <property name="alwaysAcceptDirectories" value="true" />
</bean>

Once you have defined filters such as those in the preceding example, you can use one by setting the filter property on the gateway.

See also Outbound Gateway Partial Success (mget and mput).

Using the put Command

The put command sends a file to the remote server. The payload of the message can be a java.io.File, a byte[], or a String. A remote-filename-generator (or expression) is used to name the remote file. Other available attributes include remote-directory, temporary-remote-directory, and their *-expression equivalents: use-temporary-file-name and auto-create-directory. See the schema documentation for more information.

The message payload resulting from a put operation is a String that represents the full path of the file on the server after transfer.

Version 5.2 introduced the chmod attribute, which changes the remote file permissions after upload. You can use the conventional Unix octal format (for example, 600 allows read-write for the file owner only). When configuring the adapter using java, you can use setChmod(0600). Only applies if your FTP server supports the SITE CHMOD subcommand.

Using the mput Command

The mput sends multiple files to the server and supports only one option:

  • -R: Recursive. Send all files (possibly filtered) in the directory and its subdirectories.

The message payload must be a java.io.File (or String) that represents a local directory. Since version 5.1, a collection of File or String is also supported.

This command supports the same attributes as the put command. In addition, files in the local directory can be filtered with one of mput-pattern, mput-regex, mput-filter, or mput-filter-expression. The filter works with recursion, as long as the subdirectories themselves pass the filter. Subdirectories that do not pass the filter are not recursed.

The message payload resulting from an mput operation is a List<String> object (that is, a List of remote file paths that result from the transfer).

See also Outbound Gateway Partial Success (mget and mput).

Version 5.2 introduced the chmod attribute, which lets you change the remote file permissions after upload. You can use the conventional Unix octal format (for example, 600 allows read-write for the file owner only). When configuring the adapter with Java, you can use setChmodOctal("600") or setChmod(0600). Only applies if your FTP server supports the SITE CHMOD subcommand.

Using the rm Command

The rm command removes files.

The rm command has no options.

The message payload resulting from an rm operation is Boolean.TRUE if the remove was successful or Boolean.FALSE otherwise. The file_remoteDirectory header provides the remote directory, and the file_remoteFile header provides the file name.

Using the mv Command

The mv command moves files.

The mv command has no options.

The expression attribute defines the “from” path and the rename-expression attribute defines the “to” path. By default, the rename-expression is headers['file_renameTo']. This expression must not evaluate to null or an empty String. If necessary, any necessary remote directories are created. The payload of the result message is Boolean.TRUE. The file_remoteDirectory header provides the original remote directory, and file_remoteFile header provides the file name. The new path is in the file_renameTo header.

Starting with version 5.5.6, the remoteDirectoryExpression can be used in the mv command for convenience. If the “from” file is not a full file path, the result of remoteDirectoryExpression is used as the remote directory. The same applies for the “to” file, for example, if the task is just to rename a remote file in some directory.

Additional Information about FTP Outbound Gateway Commands

The get and mget commands support the local-filename-generator-expression attribute. It defines a SpEL expression to generate the name of local files during the transfer. The root object of the evaluation context is the request message. The remoteFileName variable, which is particularly useful for mget, is also available — for example, local-filename-generator-expression="#remoteFileName.toUpperCase() + headers.something".

The get and mget commands support the local-directory-expression attribute. It defines a SpEL expression to generate the name of local directories during the transfer. The root object of the evaluation context is the request message but. The remoteDirectory variable, which is particularly useful for mget, is also available — for example: local-directory-expression="'/tmp/local/' + #remoteDirectory.toUpperCase() + headers.something". This attribute is mutually exclusive with the local-directory attribute.

For all commands, the 'expression' property of the gateway provides the path on which the command acts. For the mget command, the expression might evaluate to '', meaning to retrieve all files, or 'somedirectory/', and so on.

The following example shows a gateway configured for an ls command:

<int-ftp:outbound-gateway id="gateway1"
    session-factory="ftpSessionFactory"
    request-channel="inbound1"
    command="ls"
    command-options="-1"
    expression="payload"
    reply-channel="toSplitter"/>

The payload of the message sent to the toSplitter channel is a list of String objects that each contain the name of a file. If the command-options attribute was omitted, it holds FileInfo objects. It uses space-delimited options — for example, command-options="-1 -dirs -links".

Starting with version 4.2, the GET, MGET, PUT and MPUT commands support a FileExistsMode property (mode when using the namespace support). This affects the behavior when the local file exists (GET and MGET) or the remote file exists (PUT and MPUT). Supported modes are REPLACE, APPEND, FAIL, and IGNORE. For backwards compatibility, the default mode for PUT and MPUT operations is REPLACE. For GET and MGET operations, the default is FAIL.

Starting with version 5.0, the setWorkingDirExpression() (working-dir-expression in XML) option is provided on the FtpOutboundGateway (<int-ftp:outbound-gateway> in XML). It lets you change the client working directory at runtime. The expression is evaluated against the request message. The previous working directory is restored after each gateway operation.

Configuring with Java Configuration

The following Spring Boot application shows an example of how to configure the outbound gateway with Java configuration:

@SpringBootApplication
public class FtpJavaApplication {

    public static void main(String[] args) {
        new SpringApplicationBuilder(FtpJavaApplication.class)
            .web(false)
            .run(args);
    }

    @Bean
    public SessionFactory<FTPFile> ftpSessionFactory() {
        DefaultFtpSessionFactory sf = new DefaultFtpSessionFactory();
        sf.setHost("localhost");
        sf.setPort(port);
        sf.setUsername("foo");
        sf.setPassword("foo");
        sf.setTestSession(true);
        return new CachingSessionFactory<FTPFile>(sf);
    }

    @Bean
    @ServiceActivator(inputChannel = "ftpChannel")
    public MessageHandler handler() {
        FtpOutboundGateway ftpOutboundGateway =
                          new FtpOutboundGateway(ftpSessionFactory(), "ls", "'my_remote_dir/'");
        ftpOutboundGateway.setOutputChannelName("lsReplyChannel");
        return ftpOutboundGateway;
    }

}

Configuring with the Java DSL

The following Spring Boot application shows an example of how to configure the outbound gateway with the Java DSL:

@SpringBootApplication
public class FtpJavaApplication {

    public static void main(String[] args) {
        new SpringApplicationBuilder(FtpJavaApplication.class)
            .web(false)
            .run(args);
    }

    @Bean
    public SessionFactory<FTPFile> ftpSessionFactory() {
        DefaultFtpSessionFactory sf = new DefaultFtpSessionFactory();
        sf.setHost("localhost");
        sf.setPort(port);
        sf.setUsername("foo");
        sf.setPassword("foo");
        sf.setTestSession(true);
        return new CachingSessionFactory<FTPFile>(sf);
    }

    @Bean
    public FtpOutboundGatewaySpec ftpOutboundGateway() {
        return Ftp.outboundGateway(ftpSessionFactory(),
            AbstractRemoteFileOutboundGateway.Command.MGET, "payload")
            .options(AbstractRemoteFileOutboundGateway.Option.RECURSIVE)
            .regexFileNameFilter("(subFtpSource|.*1.txt)")
            .localDirectoryExpression("'localDirectory/' + #remoteDirectory")
            .localFilenameExpression("#remoteFileName.replaceFirst('ftpSource', 'localTarget')");
    }

    @Bean
    public IntegrationFlow ftpMGetFlow(AbstractRemoteFileOutboundGateway<FTPFile> ftpOutboundGateway) {
        return f -> f
            .handle(ftpOutboundGateway)
            .channel(c -> c.queue("remoteFileOutputChannel"));
    }

}

Outbound Gateway Partial Success (mget and mput)

When you perform operations on multiple files (by using mget and mput), an exception can occur some time after one or more files have been transferred. In this case (starting with version 4.2), a PartialSuccessException is thrown. As well as the usual MessagingException properties (failedMessage and cause), this exception has two additional properties:

  • partialResults: The successful transfer results.

  • derivedInput: The list of files generated from the request message (for example, local files to transfer for an mput).

These attributes let you determine which files were successfully transferred and which were not.

In the case of a recursive mput, the PartialSuccessException may have nested PartialSuccessException occurrences.

Consider the following directory structure:

root/
|- file1.txt
|- subdir/
   | - file2.txt
   | - file3.txt
|- zoo.txt

If the exception occurs on file3.txt, the PartialSuccessException thrown by the gateway has derivedInput of file1.txt, subdir, and zoo.txt and partialResults of file1.txt. Its cause is another PartialSuccessException with derivedInput of file2.txt and file3.txt and partialResults of file2.txt.