ConstantFunction
shibboleth.Functions.Constant constructs a Function that returns its input argument. It adapts a fixed configuration value into a Function object.
shibboleth.BiFunctions.Constant constructs a BiFunction that returns its input argument. It adapts a fixed configuration value into a BiFunction object.
They are abstract beans so require a single constructor argument, which will always be returned when the function is called.
Because of Spring's byzantine type conversion behavior, it's usually best to supply a bean of a specific type as an argument to ensure that the function returns exactly what's intended.
Example
<bean parent="shibboleth.Functions.Constant">
<constructor-arg>
<!-- Fully define the bean to return from the function here. -->
<bean class="...." />
</constructor-arg>
</bean>