com.smartgwt.client.docs

## Interface VelocityExpression

-     public interface VelocityExpression

  An expression in the Velocity Template Language (VTL). For more information on Smart GWT's Velocity support, see `Velocity support`.

  Note that a `VelocityExpression` must often evaluate to a particular type of value to be useful. For example, `DataSource.requires` must evaluate to true or false (Boolean objects or strings containing those two words), and `Mail.messageData` must evaluate to a Java `Map` object, or a Java `List` containing only `Map`s.