To Trigger a Flow When a New File is Created or Modified

Anypoint Connectors for File, FTP, and SFTP provide an On New or Updated File operation that polls a directory for files that have been created or updated. A message is generated for each file that is found.

The following strategies determine that a file is new:

Set the Auto delete field to True to delete each file after it is processed, which causes all files obtained in the next poll to be considered new.
Set the Move to directory field to move each file to a different directory after it is processed, which achieves the same effect as Auto delete but without erasing the file.
Set the Watermark field to pick only files that have been created or updated after the last poll was executed.

You can also use a matcher for additional filtering of files.

Example: File Listener (On New File Trigger)

<flow name="onNewFile">
    <file:listener config-ref="file" directory="test-data/in" autoDelete="true">
      <scheduling-strategy>
        <fixed-frequency frequency="1000"/>
      </scheduling-strategy>
    </file:listener>

    <flow-ref name="processFile" />
</flow>

Watermarking

For the File connector, the watermarking strategy can be used in two different modes: CREATION_TIMESTAMP or MODIFIED_TIMESTAMP. The strategy depends on whether you want to filter files based on their creation or modification time.

Example: Watermarking with the File Listener

<file:listener doc:name="On New File"
  config-ref="File_Config1"
  watermarkMode="CREATED_TIMESTAMP">
    <scheduling-strategy >
      <fixed-frequency />
    </scheduling-strategy>
</file:listener>

Repeatable Streams

The List operation makes use of the repeatable streams functionality introduced in Mule 4. The operation returns a list of messages, where each message represents a file in the list and holds a stream to the file. A stream is repeatable by default.

For more information, refer to Streaming in Mule 4.