Using Module Parameters

Declare a parameter for a module. We will refer to this as module B. See Declaring Module Parameters.

Reference the parameter with the syntax ${param-name} in one or more expressions in an operator or adapter in module B.

In the EventFlow canvas for a different module, A, use a Module Reference operator to call module B. See Properties: Parameters Tab.

Set the value for the parameter to use when calling B from A using the Module Reference operator's Parameters tab (or using one of the other methods described in Setting Values for Module Parameters).

Add a row for each parameter you want to declare.

Optionally specify a default value. If you do not specify a default value, the module receives a typechecking error. Depending on how the application uses the parameter, it may be necessary to specify a default value to get the application to typecheck without errors.

In the absence of a default value, you must specify a value for the parameter when you call the containing module, as described in the next section.

In the Parameters tab of the Properties view for Module References.

This is the primary method for setting module parameter values when calling modules. You can use an expression to set the value. To set a value that depends on an environment variable, use the systemenv() function.

For details about using the Parameters tab, see Properties: Parameters Tab. In particular, you may find it useful to use the Show parameter definitions link to see what parameters are defined, and the Fill All Rows button to create rows for the parameters.

In the <module-parameters> child element of the <application> element in the server configuration file.

Use this method to define values for module parameters for a module in a container. The values you specify are set when the server is started and the configuration file is loaded. The values are passed to the module when the container holding the module is started. Values specified in a <module-parameters> element can be enciphered to preserve the privacy of the information. See Enciphering Passwords and Parameter Values for details.

In the Main tab of the Run/Debug Configuration dialog when editing a Studio launch configuration, for setting parameter values for the top-level module.

In the Containers tab of the Run/Debug Configuration dialog when editing a Studio launch configuration, for setting parameter values for modules in containers.

You can use this method in Studio when starting application modules in containers.

With the sbadmin addContainer --parameter command.

With the sbargen --parameter command.

When writing your own administrative client utility with the StreamBaseAdminClient class, using the --parameter option of the addContainer() method.

Declare the same module parameter name in all modules of interest. For example, we might declare parameter param-name in modules B, C, and D.

In module A, use the Parameters tab of the Properties view of the Module Reference component that calls module B. Set a value for param-name, such as param-name=100.0.

In module B, in the Module Reference component that calls module C, use the Parameters tab to set the value of C's parameter to the same as B's: param-name=${param-name}.

In module C, in the Module Reference component that calls module D, use the same setting: param-name=${param-name}.

Declare the same module parameter name in all modules, including the top-level module. For our example, declare param-name in modules A, B, C, and D.

Set the value of param-name for A, the top-level module, when you start the container holding all four modules. Use one of methods 2 through 6 in Setting Values for Module Parameters.

Use the param-name=${param-name} syntax in the Module References for modules A, B, and C when calling modules B, C, and D, respectively.

Module parameters with values set in Module Reference operators.

Module parameters with values set with the <module-parameters> element in the configuration file.

Module parameter default values.

Global parameters with values set with the <operator-parameters> element in the configuration file.

Define module parameters in the application module.

In the following figure, we have selected the Parameters tab and defined two parameters in the GatherAlarms application:

Notice that we have set a default value for only one of the parameters. We will see later how this affects our use of the parameters.

Use the module parameters in the application module.

Let us change the volume and price expressions shown previously, as follows:

Reference the module in another application.

The following figure shows an application named UseAlarms, which simply references the GatherAlarms module twice:

Bind the parameters to values in the module reference.

Our example has two module references, and we will set the parameters differently in each one:

Define a module parameter using the CREATE PARAMETERS statement, optionally including a default value. For example:

CREATE PARAMETERS (table_name DEFAULT "TABLE1");

Reference the parameter in an expression in the application module, using the following syntax:

${table_name}

Reference the module using an APPLY MODULE statement. Within the statement, you must specify any undefined parameter values. You do not need to bind a parameter that has a default value, except when you want to override the default value. For example:

APPLY MODULE "GatherAlarms.sbapp"
  (MinVolume=4000000, MinPrice=500)
FROM Input1 = Input1
INTO Output1 = Output1;