Connect to SFTP Servers Dynamically Example - Mule 4

Many integrations require connecting to different servers based on a specific condition, such as:

  • Connecting to different invoice storage servers depending on the branch that emits an invoice

  • Connecting to different servers depending on an integration subject, such as in a multitenant use case

To accommodate these use cases, the Anypoint Connector for SFTP (SFTP Connector) global configuration element supports parameter expressions that evaluate these conditions and connect to the correct server.

The following example shows how to configure SFTP Connector to connect dynamically to multiple servers:

  1. An HTTP Listener source initiates the flow by reading random content posted via HTTP.

  2. The File Connector Read operation loads a recipients CSV file that contains a random set of SFTP destinations, with columns such as host, user, and port.

  3. A DataWeave transformation maps the content and splits the CSV file.

  4. A For Each component and an SFTP Write operation write the contents into each of the SFTP destinations.

    On each For Each iteration, the expressions set in the SFTP global configuration element resolve to a different value and establish different connections to each of the servers.

To test this example, create the Mule application, and run and test the application with curl commands:

Connect to SFTP Servers Dynamically
Figure 1. Connect to SFTP Servers Dynamically flow

Create the Mule Application

To create the Mule flow:

  1. In the Mule Palette view, select HTTP > Listener.

  2. Drag HTTP Listener to the Studio canvas.

  3. On the HTTP Listener configuration screen, optionally change the value of the Display Name field.

  4. Set the Path field to /multitenant

  5. Click the plus sign (+) next to the Connector configuration field to configure a global element that can be used by all instances of HTTP Listener in the app.

  6. On the General tab, set the following fields:

    • Host: All Interfaces [0.0.0.0] (default)

    • Port: 8081

  7. Click OK.

  8. Drag a Set Variable component to the right of the HTTP Listener source.

  9. Set the Name field to content and the Value field to #[payload].

  10. Drag the File Connector Read operation to the right of the Set Variable component.

  11. Set the File Path field to recipients.csv.
    This reads a CSV file that contains a random set of SFTP destinations with columns such as host, user, and port.

  12. Click the plus sign (+) next to the Connector configuration field to configure a global element that can be used by all instances of File Connector in the app.

  13. Accept the default settings and click OK.

  14. On the MIME Type tab of the Read operation, for the MIME Type field, select application/csv.

Configure Additional Components and Operations

Continue creating your Mule application by adding additional components and operations:

  1. In Studio, drag a Transform Message component to the right of the Read operation.

  2. In the Output section of the component, add the following DataWeave code to map the columns of the CSV file:

    DataWeave script:
    %dw 2.0
    output application/java
    ---
    payload map using (row = $) {
       host: row.Host,
       user: row.User,
       password: row.Password}
  3. Drag a For Each component to the right of the Transform Message component.

  4. Drag an SFTP Write operation into the For Each component.
    On each For Each iteration, the Write operation writes the contents into each of the SFTP destinations.

  5. Click the plus sign (+) next to the Connector configuration field to configure a global element that can be used by all instances of SFTP Write operation in the app, and set the following fields:

    • Host: #[payload.host]

    • Username: #[payload.username]

    • Password: #[payload.password]

  6. Click OK.

  7. On the configuration screen, set the Path field to demo.txt.

  8. Set the Content field to payload.

  9. Drag a Set Payload component to the right of the For Each component.

  10. Set the Value field to Multicast Ok.

Run and Test your Mule Application

After creating your Mule application, run and test it:

  1. In Studio, save your Mule app.

  2. Click the project name in Package Explorer and then click Run > Run As > Mule Application.

  3. Open a browser and type http://0.0.0.0:8081/multitenant.

Note about Mule 4 behavior for Mule 3 users:

  • The information posted through the HTTP Listener source is written to each SFTP site multiple times.

    Because the listener makes use of the repeatable streams feature, you do not need to worry about consuming the stream multiple times.

  • The For Each component automatically goes through each line of the CSV file.

    In Mule 3, you first needed to transform the CSV file into a Java structure, but because Mule 4 is now Java agnostic, this works out-of-the-box.

When reading or listing files, you might be interested in the file’s metadata (for example, the file name, full path, size, timestamp). The connector uses the Mule message attributes to access this information.

XML for Connecting to SFTP Servers Dynamically

Paste this code into your Studio XML editor to quickly load the flow for this example into your Mule app:

<?xml version="1.0" encoding="UTF-8"?>

<mule xmlns:sftp="http://www.mulesoft.org/schema/mule/sftp" xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core"
	xmlns:file="http://www.mulesoft.org/schema/mule/file"
	xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/file http://www.mulesoft.org/schema/mule/file/current/mule-file.xsd
http://www.mulesoft.org/schema/mule/ee/core http://www.mulesoft.org/schema/mule/ee/core/current/mule-ee.xsd
http://www.mulesoft.org/schema/mule/sftp http://www.mulesoft.org/schema/mule/sftp/current/mule-sftp.xsd">
	<http:listener-config name="HTTP_Listener_config" >
		<http:listener-connection host="0.0.0.0" port="8081" />
	</http:listener-config>
	<file:config name="File_Config" doc:name="File Config"  />
	<sftp:config name="SFTP_Config" doc:name="SFTP Config"  >
		<sftp:connection host="#[payload.host]" username="#[payload.user]" password="#[payload.password]" />
	</sftp:config>
	<flow name="SFTPexample" >
		<http:listener doc:name="Listener" config-ref="HTTP_Listener_config" path="/multitenant"/>
		<set-variable value="#[payload]" doc:name="Set Variable" variableName="content"/>
		<file:read doc:name="Read" config-ref="File_Config" path="recipients.csv" outputMimeType="application/csv"/>
		<ee:transform doc:name="Transform Message" >
			<ee:message >
				<ee:set-payload ><![CDATA[%dw 2.0
output application/java
---
payload map using (row = $) {
   host: row.Host,
   user: row.User,
   password: row.Password}]]></ee:set-payload>
			</ee:message>
		</ee:transform>
		<foreach doc:name="For Each" >
			<sftp:write doc:name="Write" config-ref="SFTP_Config" path="demo.txt">
			</sftp:write>
		</foreach>
		<set-payload value="Multicast OK" doc:name="Set Payload" />
	</flow>
</mule>