MyProcessEnginePlugin.java

import org.camunda.bpm.dmn.engine.DmnEngine;

public class MyProcessEnginePlugin extends AbstractProcessEnginePlugin {

  public void postInit(ProcessEngineConfigurationImpl processEngineConfiguration) {
    DmnEngine dmnEngine = processEngineConfiguration.getDmnEngineConfiguration()
      .feelEngineFactory(new CustomFeelEngineFactory())
      .buildEngine();

    processEngineConfiguration.setDmnEngine(dmnEngine);
  }

}