org.opendaylight.yangtools.yang.xpath.api

Interface YangXPathExpression

All Superinterfaces:

Immutable, MutationBehaviour<Immutable>

All Known Subinterfaces:

YangXPathExpression.QualifiedBound, YangXPathExpression.UnqualifiedBound

@Beta
public interface YangXPathExpression
extends Immutable

An XPath expression. This interface defines a parsed representation of an XPath defined in a YANG context, as specified in RFC7950, Section 6.4.

The specification along with rules for path statement evaluation rules end up defining four incremental levels to which an XPath expression can be bound:

• Unbound Expressions, which is a essentially a parse tree. No namespace binding has been performed, i.e. all node identifiers are in QualifiedQName or UnqualifiedQName form. This level is typically not used when dealing with YANG models directly, but can be useful for validating a String conforms to XPath syntax.
• Qualified-bound Expressions, where all QualifiedQNames are resolved and bound to QNames, but UnqualifiedQNames are still present. This level corresponds to how far a YANG parser can interpret XPath expressions defined in typedef statements and statements which are not fully instantiated, i.e. are descendants of a grouping statement.
• Namespace-bound Expressions, where all node identifier references are resolved to QNames. This level corresponds to how far a YANG parser can interpret XPath expressions at their place of instantiation, either in the data tree or an action/@{code rpc}/notification or similar context.
• Context-bound Expressions, where the expression is bound to a {code context node}, i.e. current() function result is know. This API does not handle this state, as it is inherently bound to a particular data object model.

Author:

Robert Varga

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	YangXPathExpression.QualifiedBound A Qualified-bound expression.
static interface	YangXPathExpression.UnqualifiedBound

Method Summary

Modifier and Type	Method and Description
YangXPathMathMode	getMathMode() Return the YangXPathMathMode used in this expression.
YangExpr	getRootExpr() Return the root YangExpr.
YangLocationPath	interpretAsInstanceIdentifier(YangLiteralExpr expr)
YangQNameExpr	interpretAsQName(YangLiteralExpr expr) Attempt to interpret a YangLiteralExpr referenced by this expression as a QName.

Method Detail

getRootExpr

YangExpr getRootExpr()

Return the root YangExpr.

Returns:

Root expression.

getMathMode

YangXPathMathMode getMathMode()

Return the YangXPathMathMode used in this expression. All YangNumberExpr objects used by this expression are expected to be handled by this mode's YangXPathMathSupport.

Returns:

YangXPathMathMode

interpretAsQName

YangQNameExpr interpretAsQName(YangLiteralExpr expr)
                        throws XPathExpressionException

Attempt to interpret a YangLiteralExpr referenced by this expression as a QName. This method is required to perform late value binding of the expression when the literal needs to be interpreted as a reference to an identity.

The syntax of expr is required to conform to XML QName format, as further restricted by YANG identityref Lexical Representation.

Unfortunately we do not know when a literal will need to be interpreted in this way, as that can only be known at evaluation.

Parameters:

expr - Literal to be reinterpreted

Returns:

YangQNameExpr result of interpretation

Throws:

XPathExpressionException - when the literal cannot be interpreted as a QName

interpretAsInstanceIdentifier

YangLocationPath interpretAsInstanceIdentifier(YangLiteralExpr expr)
                                        throws XPathExpressionException

Throws:

XPathExpressionException