Using CA AppLogic › Appliance Developer Guide › Appliance Overview › Configure Appliance › Set Class Boundary › Properties

Properties

Properties are configuration parameters used to specialize the behavior of an appliance in a specific application role. Properties work in conjunction with interface connections to specialize an individual instance.

You can define all the configuration properties that you want to be modifiable as well as fine-tune parameters, timeouts, file locations, appliance volumes, and mode of operation of the appliance. You should expose property configuration parameters that can be used by the user and cannot be fixed by the class itself.

Note: Dependencies or binding to outside services should be expressed as output terminals, not properties.

Appliances typically contain 3 to 12 properties with most having default values. You should define the most frequently changed values first.

Follow these steps:

1. On the Properties tab, define the properties by selecting the row and entering the information, as needed.
   • Name - defines the name of the configuration as it is visible on the appliance. Select a meaningful name that is intuitive in the appliance class.
   • Type - defines the type of value. The most common are string and integer.
   • Default - indicates the value that property assumes, if not explicitly configured. You cannot use a default value for a property marked as mandatory. Setting a property to an empty value is not the same as not setting a value. In empty value, the property value is set to empty. Not setting the value, sets the value to no value.
2. Set the following optional parameters, as needed.
   • Mandatory - indicates the attribute must be configured for the appliance to function. This is a design constraint. If configured and not set, the appliance fails to start. Mandatory should only be used in cases where no default can be defined. For example, the target host name in output gateways.
   • Constraints - limits the value of a property. The three types are:
     • Minimum or maximum range - allows a minimum and maximum value for integer properties. To limit only one value on the range, leave the other value empty. For example, limit the minimum value and leave the maximum value blank
     • FIlter - allows a regular expression for validating the property value. Regular expressions are very error-prone. Use this caution with this constraint or simply use the values constraint instead. The syntax of the filter is the same as the Perl regular expression pattern matching. The entire property value is validated. For example, it is as if /^filter$/ was used in a Perl statement to check for a match where filter is the value of the filter attribute. You can use the filter constraint with any property type.
     • Allowed Values - defines an enumerated set of values, such as yes|no or high|low. The syntax is literal values separated with |. Using the values constraint with the lowercase property attribute removes case sensitivity from the value set.
   • Lower Case - automatically converts the property value to lower case. This is typically used for host names.
   • Hidden - protects the value of properties that contain sensitive data, such as passwords. When you remove the hidden attribute from a property, it clears the previously set value of that property. This only applies to strings.
   • Info - displays the name, type, and protocol.
3. To add an Input Terminal, Output Terminal, or Raw Interface, click the corresponding button. .

   When adding properties, selecting the correct property type allows for IP validation. In addition, CA AppLogic can provide a set of enumerated values for a property using the linear attributes of a string or integer.

   Use string properties for general text values, integers for numerical values, and IP address-type properties to represent IP addresses of external entities, such as a DNS server. Whenever possible, use an output terminal instead of using an IP address.

4. To add an external interface, select the External Interface check box.

   An IP address can also be used in conjunction with the legacy external interface to provide unconstrained IP address selection for an appliance. In addition, the IP_owned property is used to hold the IP address for the legacy external interface. Both are supported for backward compatibility only and may be discontinued in future releases.

5. To continue, select the Resources tab.