net.sf.saxon.s9api.XPathExecutable Maven / Gradle / Ivy
Show all versions of Saxon-HE Show documentation
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.s9api;
import net.sf.saxon.expr.StaticContext;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.s9api.streams.Step;
import net.sf.saxon.sxpath.IndependentContext;
import net.sf.saxon.sxpath.XPathExpression;
import net.sf.saxon.sxpath.XPathVariable;
import net.sf.saxon.transpile.CSharpModifiers;
import java.util.*;
import java.util.stream.Stream;
/**
* An XPathExecutable represents the compiled form of an XPath expression.
* To evaluate the expression, it must first be loaded to form an {@link XPathSelector}.
* An XPathExecutable is immutable, and therefore thread-safe. It is simplest to load
* a new XPathSelector each time the expression is to be evaluated. However, the XPathSelector
* is serially reusable within a single thread.
* An XPathExecutable is created by using the {@link XPathCompiler#compile} method
* on the {@link XPathCompiler} class.
*/
@CSharpModifiers(code = {"internal"})
public class XPathExecutable {
private final XPathExpression exp;
private final Processor processor;
private final IndependentContext env;
// protected constructor
protected XPathExecutable(XPathExpression exp, Processor processor, IndependentContext env) {
this.exp = exp;
this.processor = processor;
this.env = env;
//this.declaredVariables = declaredVariables;
}
/**
* Load the compiled XPath expression to prepare it for execution.
*
* @return An XPathSelector. The returned XPathSelector can be used to set up the
* dynamic context, and then to evaluate the expression.
*/
public XPathSelector load() {
Map declaredVariables = new LinkedHashMap();
for (XPathVariable var :env.getExternalVariables()) {
declaredVariables.put(var.getVariableQName(), var);
}
return new XPathSelector(exp, declaredVariables);
}
/**
* Treat the compiled XPath expression as a {@link Step}, so that it can be used in a call on
* {@link XdmValue#select}.
*
* Example usage: node.select(c.compile(".//x[a=b+2]").asStep()).asXdmValue()
* @return a Step, whose effect is to evaluate the XPath expression (with the origin item as the
* initial context item)
*/
public Step asStep() {
return new Step() {
@Override
public Stream apply(XdmItem item) {
try {
XPathSelector selector = load();
selector.setContextItem(item);
XdmSequenceIterator result = selector.iterator();
return result.stream();
} catch (SaxonApiException e) {
throw new SaxonApiUncheckedException(e);
}
}
};
}
/**
* Get the ItemType of the items in the result of the expression, as determined by static analysis. This
* is the most precise ItemType that the processor is able to determine from static examination of the
* expression; the actual items in the expression result are guaranteed to belong to this ItemType or to a subtype
* of this ItemType.
*
* @return the statically-determined ItemType of the result of the expression
* @since 9.1
*/
public ItemType getResultItemType() {
net.sf.saxon.type.ItemType it = exp.getInternalExpression().getItemType();
return new ConstructedItemType(it, processor.getUnderlyingConfiguration());
}
/**
* Get the statically-determined cardinality of the result of the expression. This is the most precise cardinality
* that the processor is able to determine from static examination of the expression.
*
* @return the statically-determined cardinality of the result of the expression
* @since 9.1
*/
public OccurrenceIndicator getResultCardinality() {
int card = exp.getInternalExpression().getCardinality();
return OccurrenceIndicator.getOccurrenceIndicator(card);
}
/**
* Get an iterator over the names of all the external variables. This includes both variables that have
* been explicitly declared using a call to declareVariable(), and variables that are implicitly
* declared by reference in the case where the allowUndeclaredVariables option is set. It does
* not include range variables bound in a for, some, or every expression.
* If the allowUndeclaredVariables option is set, this method allows discovery of the variable
* references that appear in the compiled expression.
*
* @return an iterator over the names of the external variables defined in the XPath expression
* @since 9.2
*/
public Iterator iterateExternalVariables() {
List list = new ArrayList<>();
for (XPathVariable var : env.getExternalVariables()) {
list.add(new QName(var.getVariableQName()));
}
return list.iterator();
}
/**
* Get the required item type of a declared variable in the static context of the expression.
*
* @param variableName the name of a declared variable
* @return the required item type.
* If the variable was explicitly declared, this will be the item type that was set when the
* variable was declared. If no item type was set, it will be {@link ItemType#ANY_ITEM}.
* If the variable was implicitly declared by reference (which can happen only when the
* allowUndeclaredVariables option is set), the returned type will be {@link ItemType#ANY_ITEM}.
* If no variable with the specified QName has been declared either explicitly or implicitly,
* the method returns null.
* @since 9.2
*/
/*@Nullable*/
public ItemType getRequiredItemTypeForVariable(QName variableName) {
XPathVariable var = env.getExternalVariable(variableName.getStructuredQName());
if (var == null) {
return null;
} else {
return new ConstructedItemType(var.getRequiredType().getPrimaryType(), processor.getUnderlyingConfiguration());
}
}
/**
* Get the required cardinality of a declared variable in the static context of the expression.
*
* @param variableName the name of a declared variable
* @return the required cardinality.
* If the variable was explicitly declared, this will be the occurrence indicator that was set when the
* variable was declared. If no item type was set, it will be {@link OccurrenceIndicator#ZERO_OR_MORE}.
* If the variable was implicitly declared by reference (which can happen only when the
* allowUndeclaredVariables option is set), the returned type will be
* {@link OccurrenceIndicator#ZERO_OR_MORE}.
* If no variable with the specified QName has been declared either explicitly or implicitly,
* the method returns null.
* @since 9.2
*/
public OccurrenceIndicator getRequiredCardinalityForVariable(QName variableName) {
XPathVariable var = env.getExternalVariable(variableName.getStructuredQName());
if (var == null) {
return null;
} else {
return OccurrenceIndicator.getOccurrenceIndicator(var.getRequiredType().getCardinality());
}
}
/**
* Get the underlying implementation object representing the compiled XPath expression.
* This method provides access to lower-level Saxon classes and methods which may be subject to change
* from one release to the next.
*
* @return the underlying compiled XPath expression.
*/
public XPathExpression getUnderlyingExpression() {
return exp;
}
/**
* Get the underlying implementation object representing the static context of the compiled
* XPath expression. This method provides access to lower-level Saxon classes and methods which may be
* subject to change from one release to the next.
*
* @return the underlying static context.
*/
public StaticContext getUnderlyingStaticContext() {
return env;
}
}