Set Variable Transformer
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Standard Support for Mule 4.1 ended on November 2, 2020, and this version of Mule reached its End of Life on November 2, 2022, when Extended Support ended. Deployments of new applications to CloudHub that use this version of Mule are no longer allowed. Only in-place updates to applications are permitted. MuleSoft recommends that you upgrade to the latest version of Mule 4 that is in Standard Support so that your applications run with the latest fixes and security enhancements. |
The Set Variable (set-variable) component is for creating or updating a variable to store values for use within the flow of a Mule app. You can store simple literal values such as strings or messages, message payloads, or attribute objects. For example, you might store the original payload of a message (before it is processed) so you can use it later in the flow or within an error handler.
The set-variable component is not recommended for complex expressions or transformations. You should instead use it for simple ones, such as selections, and use the Transform Component
for complex scenarios.
| Field | Usage | Description |
|---|---|---|
Variable Name ( |
Required |
Name of the variable. Names can only include numbers, characters, and underscores. For example, hyphens are not allowed in the name. |
Value ( |
Required |
Value for the variable, which can be a string or a DataWeave expression. |
Mime Type ( |
Optional |
Sets the variable MIME type, such as |
Encoding ( |
Optional |
Sets the variable encoding, such as |
|
The |
Examples
This example sets the variable to a string:
-
Name =
myVar -
Value =
my first variable
This example sets the variable by using a DataWeave operation that results in a value of 5:
-
Name =
myVar -
Value =
#[max([1,2,3] ++ [3,4,5])]in Anypoint Studio.
This example sets the variable to the message payload:
-
Name =
myVar -
Value =
payloadin Design Center,#[payload]in Anypoint Studio.
This example sets the variable to the message attributes:
-
Name =
myVar -
Value =
attributesin Design Center,#[attributes]in Anypoint Studio.
This example sets the variable to the entire message:
-
Name =
myVar -
Value =
messagein Design Center,#[message]in Anypoint Studio.
This XML example sets a variable that takes a map as a value:
<set-variable variableName="employee" value="{ 'name' : 'Ana', 'office' : 'BA' }" mimeType="application/json" encoding="UTF-8"/>
This example sets the same variable using selectors in a DataWeave script. It assumes the name attribute is available as input to Set Variable:
<set-variable variableName="employee" value="#[output application/java --- payload.name]"/>
These examples set the variable to a Boolean value, true:
-
Name =
myVar -
Value =
-
truein Design Center,#[true]in Anypoint Studio -
true as Booleanin Design Center,#[true as Boolean]in Anypoint Studio -
(1 + 1 == 2)evaluates totruein Design Center,#[(1 + 1 == 2)]evaluates totruein Anypoint Studio
-
To display the value of a variable through the Logger component in Design Center, you might need to use the Anypoint Studio syntax to display the value of a variable, for example, #[vars.myVar] instead of vars.myVar.
Accessing Variables in Other Event Processors
Set Variable sets a variable in the current Mule event, and the variables then travel with the Mule event to downstream event processors. You can access any variable with DataWeave using vars. So if you set a variable named lastMessage, you can access it as vars.lastMessage. You can set variables in a Transform Message component, and also many connectors and event processors have a Target that can be set in the Advanced tab. These all set flow variables and they are accessed the same way, through the keyword vars..