com.orchestranetworks.schema

Interface ValueFunction

public interface ValueFunction

Computes a value when this value is not persisted by EBX® repository.

Examples of uses

• to retrieve data persisted in a third-party database;
• to compute a value (the computation may depend on other values in the same dataset or record).

Definition in the data model

The specific function must be declared under the element xs:annotation/xs:appinfo (see Computed Values):

 <osd:function class="com.foo.MyFunction"/>
 

where com.foo.MyFunction is the fully qualified name of the class implementing this interface. It is also possible to set additional JavaBean properties:

 <osd:function class="com.foo.MyFunction">
          <param1>...</param1>
          <param2>...</param2>
 </osd:function>
 

where param1 and param2 are JavaBean properties of the class specified.

For more information, see the JavaBean specification.

Life cycle

1. When the data model is loaded:
   1. the class specified is instantiated through its default constructor and the setters of the JavaBean properties are called (in the example above, setParam1(...) and setParam2(...));
   2. the method setup(ValueFunctionContext) is called on the new instance.
2. During the operational phase: the method getValue(Adaptation) is called each time this is needed (for example when the record is displayed or exported).

Performance warning

See getValue(Adaptation).

Method Summary

Modifier and Type	Method and Description
Object	getValue(Adaptation aDataSetOrRecord) Returns the value in the context of the specified record or dataset.
void	setup(ValueFunctionContext aContext) This method is called when the data model is loaded, for checking that this function is consistent with the data model that defines it.

Method Detail

getValue

Object getValue(Adaptation aDataSetOrRecord)

Returns the value in the context of the specified record or dataset.

The value returned must conform to the associated data model declaration (that is, the type, cardinality, facets).

Performance warning

If the function is attached to a table with N records, some operations will call this method N times. This is the case for:

• an external export (but the method ExportSpec.setIncludesComputedValues(boolean) will deactivate the call to the function);
• a filter, when the filter depends on this node;
• full dataset validation, when the node is used by some dynamic constraints. It is however possible to avoid this call if the validation is disabled on the associated node by specifying in the data model the attribute osd:disableValidation = "true".

Thus, for a table with large volumes of records, it may be necessary to optimize the implementation (for example, by caching). See also performance guidelines chapter.

Multi-threading

For a single instance of this interface, this method may be called concurrently by several threads.

See Also:

ValueAccessException

setup

void setup(ValueFunctionContext aContext)

This method is called when the data model is loaded, for checking that this function is consistent with the data model that defines it.