code: public static Expression getFieldExpression(DelegateTask task,
                                                  String fieldName) {
          if (task.getCurrentActivitiListener() != null) {
              List<FieldExtension> fieldExtensions = task.getCurrentActivitiListener().getFieldExtensions();
              if (fieldExtensions != null && fieldExtensions.size() > 0) {
                  for (FieldExtension fieldExtension : fieldExtensions) {
                      if (fieldName.equals(fieldExtension.getFieldName())) {
                          return createExpressionForField(fieldExtension);
                      }
                  }
              }
          }
          return null;
      }
docs: Similar to {@link #getFieldExpression(DelegateExecution, String)}, but for use within a {@link TaskListener}.