> ## Documentation Index
> Fetch the complete documentation index at: https://docs.aseeflow.org/llms.txt
> Use this file to discover all available pages before exploring further.

# FEEL Engine Type Handling

This documentation covers supported types of variable values when used in a FEEL expression and
supported output types.

In DMN, when defining a `typeRef` attribute on a **Variable**, **Input** or **Output** element, the
DMN Engine tries to convert the result value of the corresponding **Literal Expression**,
**Input Expression** or the **Output Entry**. When no `typeRef` attribute is specified, the DMN
Engine passes the return value of the FEEL Engine directly without any conversion. Please see the
documentation about [Supported Data Types in DMN] to learn more about the `typeRef` attribute.

The FEEL Engine might support more types than listed below. However, this page defines
which of the types are known for being...

* ...well integrable in ASEE Flow
* ...covered by automated tests

### Supported Variable Value Types

The variable value types listed in this section can be handled by the FEEL Engine when passing.

#### Java Native Types

* `java.lang.String`
* `java.lang.Float`
* `java.lang.Double`
* `java.lang.Integer`
* `java.lang.Long`
* `java.lang.Boolean`
* `java.util.Date`
* `java.util.Map`
* `java.util.List`

#### Spin Types

* `org.camunda.spin.json.SpinJsonNode`
* `org.camunda.spin.xml.SpinXmlElement`

For more information about the ASEE Flow Spin integration, please see the documentation about
[FEEL Engine Spin Integration].

### Return Types

The table displays:

* Which return value of a FEEL Expression maps to which Java type
* Which ASEE Flow specific variable type is assigned for the respective Java type

<table class="table table-striped">
  <tr> <th>FEEL Expression Example</th> <th>FEEL Engine Return Type</th> <th>ASEE Flow Variable Type</th> </tr>
  <tr> <td><code>null</code></td> <td><code>null</code></td> <td>null</td> </tr>
  <tr> <td><code>"foo"</code></td> <td><code>java.lang.String</code></td> <td>string</td> </tr>
  <tr> <td><code>3.1415</code></td> <td><code>java.lang.Double</code></td> <td>double</td> </tr>
  <tr> <td><code>3</code></td> <td><code>java.lang.Long</code></td> <td>long</td> </tr>
  <tr> <td><code>true</code></td> <td><code>java.lang.Boolean</code></td> <td>boolean</td> </tr>
  <tr> <td><code>time("11:45:30")</code></td> <td><code>java.time.LocalTime</code></td> <td>object</td> </tr>
  <tr> <td> <code>time("11:45:30+02:00")</code><br /> <code>time("10:31:10\@Europe/Paris")</code> </td> <td><code>org.camunda.feel.syntaxtree.ZonedTime</code></td> <td>object</td> </tr>
  <tr> <td><code>date("2017-03-10")</code></td> <td><code>java.time.LocalDate</code></td> <td>object</td> </tr>
  <tr> <td><code>date and time("2019-08-12T22:22:22")</code></td> <td><code>java.time.LocalDateTime</code></td> <td>object</td> </tr>
  <tr> <td> <code>date and time("2019-08-12T22:22:22+02:00")</code><br /> <code>date and time("2019-08-12T22:22:22\@Europe/Berlin")</code> </td> <td><code>java.time.ZonedDateTime</code></td> <td>object</td> </tr>
  <tr> <td><code>duration("P4D")</code></td> <td><code>java.time.Duration</code></td> <td>object</td> </tr>
  <tr> <td><code>duration("P1Y6M")</code></td> <td><code>java.time.Period</code></td> <td>object</td> </tr>
  <tr> <td><code>\{ "foo": "bar" }</code></td> <td><code>java.util.Map</code> \*</td> <td>object</td> </tr>
  <tr> <td><code>\[ "foo", "bar", "baz" ]</code></td> <td><code>java.util.List</code> \*</td> <td>object</td> </tr>
</table>

\* Since the FEEL Engine is based on the [Scala Library], a Scala-specific implementation type for
`Map` and `List` is used

[Supported Data Types in DMN]: /user-guide/dmn-engine/data-types#supported-data-types

[FEEL Engine Spin Integration]: /user-guide/dmn-engine/feel/spin-integration

[Scala Library]: https://www.scala-lang.org/