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Messages and Values

Messages in Pipelines​

A message flows through a pipeline from pipe to pipe. Each pipe receives an input message, processes it, and produces an output message. The Frank!Framework stores the incoming pipeline message in the session key originalMessage automatically.

Session Keys​

Session keys act as variables that hold the same kind of data as the message flowing through the pipeline. The framework automatically sets:

  • originalMessage — the pipeline's input message
  • httpMethod — the HTTP method (when using an ApiListener)

Custom session keys can be written with PutInSessionPipe:

<PutInSessionPipe name="save" sessionKey="saved"/>

Default Input Behavior​

  • The first pipe in a pipeline receives the pipeline's input message.
  • Subsequent pipes receive the previous pipe's output message as input.

Override this with:

  • getInputFromSessionKey — use a session key value as input
  • getInputFromFixedValue — use a literal string as input

These attributes are defined by AbstractPipe and available on all pipes.

<ReplacerPipe name="replace" getInputFromFixedValue="Property value ${my.property} and parameter value ?{my.param}">
    <Param name="my.param" value="My parameter value"/>
</ReplacerPipe>

Property References​

Properties are referenced with ${property.name} syntax:

${my.property}

Properties come from properties files (e.g., DeploymentSpecifics.properties) or the application environment.

Parameter References​

Parameters are referenced with ?{param.name} syntax:

?{my.param}

Parameters are defined using <Param> child elements on a pipe or sender.

Context Keys​

Messages carry additional key/value pairs called context keys. When an ApiListener captures an HTTP request, it adds HTTP headers as context keys:

  • Header.content-type — the Content-Type header value
  • Other HTTP headers follow the pattern Header.<header-name>

Context keys are visible in Ladybug via the "Show messagecontext" button.

Param Element​

The <Param> element fetches values for use in pipes and senders. It can access:

  • Fixed values (value attribute)
  • Session keys (sessionKey attribute)
  • Context keys (contextKey attribute on a session key reference)

Example reading a context key from originalMessage:

<ReplacerPipe name="contentType" getInputFromFixedValue="?{context.value}">
    <Param name="context.value" sessionKey="originalMessage" contextKey="Header.content-type"/>
</ReplacerPipe>

Only the <Param> element can obtain context key values. The parameter must then be referenced by the pipe to produce the output.

ReplacerPipe Pattern Substitution​

ReplacerPipe substitutes both property references (${...}) and parameter references (?{...}) in its input. When the find attribute is omitted, no text replacement occurs — only property and parameter substitution.

<ReplacerPipe name="replace" getInputFromFixedValue="Property value ${my.property} and parameter value ?{my.param}">
    <Param name="my.param" value="My parameter value"/>
</ReplacerPipe>

Output: Property value My property value and parameter value My parameter value

EchoPipe Property Substitution​

EchoPipe substitutes properties only (${...}). It does not substitute parameters (?{...}).

Complete Example​

<Configuration
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="../FrankConfig.xsd"
>
    <Adapter name="values">
        <Receiver>
            <ApiListener name="values" method="POST" uriPattern="values" allowAllParams="true" />
        </Receiver>
        <Pipeline>
            <PutInSessionPipe name="save" sessionKey="saved"/>
            <ReplacerPipe name="replace" getInputFromFixedValue="Property value ${my.property} and parameter value ?{my.param}">
                <Param name="my.param" value="My parameter value"></Param>
            </ReplacerPipe>
            <ReplacerPipe name="contentType" getInputFromFixedValue="?{context.value}">
                <Param name="context.value" sessionKey="originalMessage" contextKey="Header.content-type"/>
            </ReplacerPipe>
        </Pipeline>
    </Adapter>
</Configuration>

Sending a request:

curl -i -X POST -H 'Content-Type: application/text' http://localhost/api/values -d 'Something'
  • First pipe (save): stores Something in session key saved
  • Second pipe (replace): outputs Property value My property value and parameter value My parameter value
  • Third pipe (contentType): outputs application/text