User-Configured Payload Transforms

Message payloads going through a workflow can be transformed using a Spring Expression Language (SpEL) expression as follows:

# <workflow-id> : The workflow ID ([0-19])
# <expression> : A SpEL expression
                 
solace.connector.workflows.<workflow-id>.transform-payloads.expressions[0].transform=<expression>

A SpEL expression may reference:

  • payload:: To access the message payload.

  • headers.<header_name>: To access a message header value.

  • Registered functions.

While the syntax uses an array of expressions, only a single transform expression is supported in this release. Multiple transform expressions may be supported in the future.

Registered Functions

Registered functions are built-in and can be called directly from SpEL expressions. To call a registered function, use the # character followed by the function name. The following table describes the available registered functions:

Registered Function Signature Description

boolean isPayloadBytes(Object obj)

Returns whether the object obj is an instance of byte[] or not.

Sample usage of this function within a SpEL expression:
"#isPayloadBytes(payload) ? true : false"

Example 1: To normalize byte[] and String payloads as upper-cased String payloads or leave payloads unchanged when of different types:

solace.connector.workflows.0.transform-payloads.expressions[0].transform
="#isPayloadBytes(payload) ? new String(payload).toUpperCase() : payload instanceof 
T(String) ? payload.toUpperCase() : payload"

Example 2: To convert String payloads to byte[] payloads using a charset retrieved from a message header or leave payloads unchanged when of different types:

solace.connector.workflows.0.transform-payloads.expressions[0].transform="payload 
instanceof T(String) ? 
payload.getBytes(T(java.nio.charset.Charset).forName(headers.charset)) : payload"

For more information about Spring Expression Language (SpEL) expressions, see Spring Expression Language (SpEL).