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Property Transformer Reference

Mule Runtime Engine versions 3.5, 3.6, and 3.7 reached End of Life on or before January 25, 2020. For more information, contact your Customer Success Manager to determine how you can migrate to the latest Mule version.

Use a property tranformer to set, remove, or copy properties on the outbound scope of message. This transformer only outbound properties. Note that you cannot manipulate inbound scope properties, as those are automatically generated by the message source. To learn more about message scopes, refer to [Mule Concepts].

The property transformer differs from the variable transformer and the sessions variable transformer. Refer to the table below for a comparison of these three transformers.

Property Transformer Variable Transformer Session Variable Transformer

Use

Use to set, remove, or copy properties on the outbound scope of a message.

Use to set or remove a variable on the message, tied to the current flow.

Use to set or remove a variable that is tied to the current message for its entire lifecycle, across multiple flows, applications, and even servers.

Persistence

Once a message hits an outbound-connector, all properties in the outbound scope are sent with the message, in the form of transport-specific metadata (HTTP headers for an HTTP outbound-connector, for example).

Variables set with a variable transformer persist only for the current flow and cannot cross the transport barrier.

Session variables set with a session variable transformer persist for the entire message lifecycle, regardless of transport barriers.

To access the property that you have set on a message earlier in a flow, or in a different flow in the application, use a MEL expression. For example, if you want to route message according to the timeStamp property you added to the header earlier in processing, you can use an expression in a choice router to access the outboundProperties property and route accordingly. Refer to the example below, where the expression #[message.outboundProperties=timeStamp] accesses the timeStamp property and evaluates to the value of property.

<choice doc:name="Choice">
    <when expression="#[message.outboundProperties['timeStamp']]">
        <logger level="INFO" doc:name="Logger"/>
    </when>
    <otherwise>
    ...
    </otherwise>
</choice>

Configuration

Studio Visual Editor

property_trans
Field Value Description XML

Display Name

Property

Customize to display a unique name for the transformer application.

doc:name="Property"

Operation

Set Property

Select to set a new property on the outbound scope of your message (as shown in the example above).

<set-property>

Remove Property

Select to delete an existing property from the inbound scope onto the outbound scope of your message

<remove-property>

Copy Properties

Select to copy an existing property from the inbound scope onto the outbound scope of your message

<copy-properties>

Name

String of Mule Expression

Specify the name for the property that you are copying or removing. If you are copying or removing properties, this field accepts a wildcard "^" character.

propertyName="MyNewPropertyName"

Value

String of Mule Expression

This field displays only if you are setting a new property. Specify the value using either a string or a Mule Expression, as shown in the example screenshot above.

value="MyNewPropertyValue"

XML Editor or Standalone

#Set property

<set-property propertyName="Authorization"  doc:name="Set Authentication Header" value="#[&quot;Basic &quot; + Base64.encodeBase64String(&quot;username:password&quot;)]"/>


# Remove property

<remove-property propertyName="PropertyForRemoval" doc:name="Delete Property"/>


# Copy property

<copy-properties propertyName="http.*" doc:name="Copy All HTTP Headers"/>
Element Description

set-property

Set a new property on the outbound scope of your message (as shown in example below).

remove-property

Delete an existing property from your message to remove it from the outbound scope.

copy-properties

Copy an existing property from the inbound scope onto the outbound scope of your message.
Element Attribute Description

doc:name

Customize to display a unique name for the transformer in your application, as shown in the example below.

Attribute not required in Mule Standalone configuration.

propertyName

The name of the property that you are setting, copying, or removing. Can be string or a Mule expression.

If you are using the remove=property or copy-properties element, you may use a wildcard "^" character. For example, a copy-properties transformer with a property name "http" will copy all properties whose names begin with "http" from the inbound scope to the outbound scope.

value

The value of the property that you are setting. This attribute is only relevant for the set-property element. Can be a string or Mule expression.

Example

In the example below, we want to connect to a web service protected by an [HTTP basic authentication] mechanism. In order to do that, our HTTP request needs to include a header, Authorization, which contains the username and password that allows the request go through. The properties transformer shown below sets an outbound property named Authorization and applies the value that is required to authenticate the message. The HTTP transport turns this outbound property into an HTTP header.

Studio Visual Editor

property_trans_example

XML Editor or Standalone

<flow name="PropertyTransformingFlow" doc:name="PropertyTransformingFlow">
   <http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8081" doc:name="HTTP"/>
      <set-property propertyName="Authorization"  doc:name="Set Authentication Header" value="#[&quot;Basic &quot; + Base64.encodeBase64String(&quot;username:password&quot;)]"/>
   <http:outbound-endpoint exchange-pattern="request-response" host="localhost" port="8081" method="POST" doc:name="HTTP"/>
</flow>

Complete Code Example

Namespace:

<mule 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:spring="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="

http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd

http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd">

Body:

<flow name="PropertyTransformingFlow" doc:name="PropertyTransformingFlow">
   <http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8081" doc:name="HTTP"/>
      <set-property propertyName="Authorization"  doc:name="Set Authentication Header" value="#[&quot;Basic &quot; + Base64.encodeBase64String(&quot;username:password&quot;)]"/>
      <remove-property propertyName="PropertyForRemoval" doc:name="Delete Property"/>
      <copy-properties propertyName="http.*" doc:name="Copy All HTTP Headers"/>
   <http:outbound-endpoint exchange-pattern="request-response" host="localhost" port="8081" method="POST" doc:name="HTTP"/>
</flow>

Referencing Properties Elsewhere

After you have set a new property, how can you call it and use it elsewhere in your flow?

  • If you select any component in your flow that precedes the creation of the property, you will see it in the Metadata Explorer, under the Outbound Properties section.

    properties+metadata+explorer

  • You can reference it an any field in any component that accepts [Mule Expression Language (MEL)], calling it through the following expression:

#[message.outboundProperties.propertyName]

In Studio, the autocomplete feature can help you out by displaying a list of available properties at that particular part of the flow.

properties+autocomplete

  • You can reference it any custom Java Class, calling it through the following:

    message.getOutboundProperty("propertyName");

    See a basic Java Class that implements this

    package org.mule.transformers;
import org.mule.api.MuleMessage;
import org.mule.api.transformer.TransformerException;
import org.mule.transformer.AbstractMessageTransformer;

public class setPropertyAsPayload extends AbstractMessageTransformer{
    /**
     * @param args
     */
    public Object transformMessage(MuleMessage message, String outputEncoding) throws TransformerException {

        String newPayload = message.getOutboundProperty("myProperty");
        return newPayload;
    }
}

    This Java Class takes an existing property named myProperty and makes it into the message payload.

See Also

  • Refer to [Mule Concepts] to learn more about message scopes.

  • Read about related transformers, the [variable transformer] and the [session variable transformer], which you can use to set variables for different scopes.

  • Learn how to use Mule Expression Language (MEL) to read and, when allowed, manipulate properties using [inboundProperties and outboundProperties maps].