Expression (org.ow2.authzforce:authzforce-ce-core-pdp-api 18.0.1 API)

Type Parameters:

V - type of result from evaluating the expression

All Known Subinterfaces:

AttributeDesignatorExpression<AV>, AttributeSelectorExpression<AV>, VariableReference<V>

All Known Implementing Classes:

ConstantExpression, ConstantPrimitiveAttributeValueExpression, FunctionExpression, GenericAttributeProviderBasedAttributeDesignatorExpression
```
public interface Expression<V extends Value>
```
Super interface of any kinds of expression in a policy that the PDP evaluation engine may evaluate in a given authorization request context:
- AttributeValue
- Apply
- AttributeSelector
- VariableReference
- AttributeDesignator
- Function

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`V`	`evaluate(EvaluationContext context)`	Evaluates the expression using the given context.
`Datatype<V>`	`getReturnType()`	Gets the expected return type of the expression if evaluated.
`Optional<V>`	`getValue()`	Get the constant value of this expression if it has a constant value, i.e.

- Method Detail
  - getReturnType
```
Datatype<V> getReturnType()
```
    Gets the expected return type of the expression if evaluated.
    
    Returns:
    
    expression evaluation's return type
  - evaluate
```
V evaluate(EvaluationContext context)
    throws IndeterminateEvaluationException
```
    Evaluates the expression using the given context.
    
    Parameters:
    
    context - the representation of the request
    
    Returns:
    
    the result of evaluation that may be a single value T (e.g. function result, AttributeValue, Condition, Match...) or bag of values (e.g. AttributeDesignator, AttributeSelector)
    
    Throws:
    
    IndeterminateEvaluationException - if evaluation is "Indeterminate" (see XACML core specification)
  - getValue
```
Optional<V> getValue()
```
    Get the constant value of this expression if it has a constant value, i.e. independent from the evaluation context (e.g. AttributeValue, VariableReference to AttributeValue...). This is equivalent to call evaluate(EvaluationContext) with context == null. This enables expression consumers to do optimizations, e.g. functions may pre-compile/pre-evaluate parts of their inputs knowing some are constant values.
    
    Returns:
    
    the constant value iff the expression has a static/fixed/constant value, else no present value. NB: Null is not considered/possible as a constant value for expressions.