Camunda BPM supports template engines which are implemented as script engines compatible with JSR-223. As a result, templates can be used everywhere where scripts can be used.

In community distributions of Camunda BPM, the following template engine is provided out of the box:

• FreeMarker

The following template engine is provided as optional add-on:

• Apache Velocity

The script engine wrapper implementations can be found in the camunda-template-engines repository.

Additionally, the following template engine is supported as enterprise extension:

• XSLT

Install a Template Engine

Install a Template Engine for an Embedded Process Engine

A template engine must be installed in the same way as a script engine. This means that the template engine must be added to the process engine classpath.

When using an embedded process engine, the template engine libraries must be added to the application deployment. When using the process engine in a maven war project, the template engine dependencies must be added as dependencies to the maven pom.xml file:

<dependencies>

  <!-- freemarker -->
  <dependency>
    <groupId>org.camunda.template-engines</groupId>
    <artifactId>camunda-template-engines-freemarker</artifactId>
  </dependency>

  <!-- apache velocity -->
  <dependency>
    <groupId>org.camunda.template-engines</groupId>
    <artifactId>camunda-template-engines-velocity</artifactId>
  </dependency>

</dependencies>

Install a Template Engine for a Shared Process Engine

When using a shared process engine, the template engine must be added to the shared process engine classpath. The procedure for this depends on the application server. In Apache Tomcat, the libraries have to be added to the shared lib/ folder.

Use a Template Engine

If the template engine library is in the classpath, you can use templates everywhere in the BPMN process where you can use scripts, for example as a script task or inputOutput mapping. The FreeMarker template engine is part of the Camunda BPM distribution.

Inside the template, all process variables of the BPMN element scope are available. The template can also be loaded from an external resource as described in the script source section.

The following example shows a FreeMarker template, of which the result is saved in the process variable text.

<scriptTask id="templateScript" scriptFormat="freemarker" camunda:resultVariable="text">
  <script>
    Dear ${customer},

    thank you for working with Camunda BPM ${version}.

    Greetings,
    Camunda Developers
  </script>
</scriptTask>

In an inputOutput mapping it can be very useful to use an external template to generate the payload of a camunda:connector.

<bpmn2:serviceTask id="soapTask" name="Send SOAP request">
  <bpmn2:extensionElements>
    <camunda:connector>
      <camunda:connectorId>soap-http-connector</camunda:connectorId>
      <camunda:inputOutput>

        <camunda:inputParameter name="soapEnvelope">
          <camunda:script scriptFormat="freemarker" resource="soapEnvelope.ftl" />
        </camunda:inputParameter>

        <!-- ... remaining connector config omitted -->

      </camunda:inputOutput>
    </camunda:connector>
  </bpmn2:extensionElements>
</bpmn2:serviceTask>

Use XSLT as Template Engine

Install the XSLT Template Engine

The XSLT Template Engine can be downloaded from the Enterprise Edition Download page.

Instructions on how to install the template engine can be found inside the downloaded distribution.

Use XSLT Template Engine with an embedded process engine

When using an embedded process engine, the XSLT template engine library must be added to the application deployment. When using the process engine in a maven war project, the template engine dependency must be added as dependencies to the maven pom.xml file:

<dependencies>

  <!-- XSLT -->
  <dependency>
    <groupId>org.camunda.bpm.extension.xslt</groupId>
    <artifactId>camunda-bpm-xslt</artifactId>
  </dependency>

</dependencies>

Use XSLT Templates

The following is an example of a BPMN ScriptTask used to execute an XSLT Template:

<bpmn2:scriptTask id="ScriptTask_1" name="convert input"
                  scriptFormat="xslt"
                  camunda:resource="org/camunda/bpm/example/xsltexample/example.xsl"
                  camunda:resultVariable="xmlOutput">

  <bpmn2:extensionElements>
    <camunda:inputOutput>
      <camunda:inputParameter name="camunda_source">${customers}</camunda:inputParameter>
    </camunda:inputOutput>
  </bpmn2:extensionElements>

</bpmn2:scriptTask>

As shown in the example above, the XSL source file can be referenced using the camunda:resource attribute. It may be loaded from the classpath or the deployment (database) in the same way as described for script tasks.

The result of the transformation can be mapped to a variable using the camunda:resultVariable attribute.

Finally, the input of the transformation must be mapped using the special variable camunda_source using a <camunda:inputParameter ... /> mapping.

A full example of the XSLT Template Engine in Camunda BPM can be found in the examples repository..