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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.xpath;
import net.sf.saxon.Configuration;
import net.sf.saxon.expr.*;
import net.sf.saxon.expr.instruct.Executable;
import net.sf.saxon.expr.instruct.SlotManager;
import net.sf.saxon.functions.Number_1;
import net.sf.saxon.om.*;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.wrapper.VirtualNode;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.DoubleValue;
import net.sf.saxon.value.NumericValue;
import org.xml.sax.InputSource;
import javax.xml.namespace.QName;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.sax.SAXSource;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
/**
* The JAXP XPathExpression interface represents a compiled XPath expression that can be repeatedly
* evaluated. This class is Saxon's implementation of that interface.
* The class also includes some methods retained from Saxon's original XPath API. When these methods
* are used, the object contains the context node and other state, so it is not thread-safe.
*
*/
public class XPathExpressionImpl implements XPathExpression {
private final Configuration config;
private final Executable executable;
private final Expression expression;
private Expression atomizer;
private SlotManager stackFrameMap;
/**
* The constructor is protected, to ensure that instances can only be
* created using the compile() method of XPathEvaluator
*
* @param exp the compiled expression
* @param exec the executable
*/
protected XPathExpressionImpl(Expression exp, /*@NotNull*/ Executable exec) {
expression = exp;
executable = exec;
config = exec.getConfiguration();
}
/**
* Define the number of slots needed for local variables within the expression.
* This method is for internal use only.
*
* @param map description of the stack frame
*/
protected void setStackFrameMap(SlotManager map) {
stackFrameMap = map;
}
/**
* Get the stack frame map. This holds information about the allocation of slots to variables.
* This is needed by applications using low-level interfaces for evaluating the expression
*
* @return a description of the stack frame
*/
public SlotManager getStackFrameMap() {
return stackFrameMap;
}
/**
* Get the Configuration under which this XPath expression was compiled
*
* @return the Saxon configuration
*/
public Configuration getConfiguration() {
return config;
}
/**
* JAXP 1.3 evaluate() method
*
* @param node The context node: generalized in Saxon to allow any XDM item to act as the context item.
* The types of values accepted, and the conversions applied, are described in the Saxon
* documentation.
*
Contrary to the interface specification, Saxon does not supply an empty
* document when the value is null. This is because XPath 2.0 allows the context
* item to be "absent" (null). So Saxon executes the XPath expression with the
* context item undefined.
* @param qName Indicates the type of result required. This must be one of the constants defined in
* the JAXP {@link XPathConstants} class.
* Saxon will attempt to convert the actual result of the expression to the required type using the
* XPath 1.0 conversion rules.
* @return the result of the evaluation, as a Java object of the appropriate type. Saxon interprets the
* rules as follows:
*
* Return value types
* QName Return Value BOOLEAN
* The effective boolean value of the actual result,
* as a Java Boolean object STRING
* The result of applying the string() function to the actual result,
* as a Java String object NUMBER
* The result of applying the number() function to the actual result,
* as a Java Double object NODE
* A single node, in the native data model supplied as input. If the
* expression returns more than one node, the first is returned. If
* the expression returns an empty sequence, null is returned. If the
* expression returns an atomic value, or if the first item in the
* result sequence is an atomic value, an exception is thrown. NODESET
* This is interpreted as allowing any sequence, of nodes or atomic values.
* If the first argument is a wrapper around a DOM Node, then the result is
* returned as a DOM NodeList, and an exception is then thrown if the result sequence
* contains a value that is not a DOM Node. In all other cases
* the result is returned as a Java List object, unless it is empty, in which
* case null is returned. The contents of the list may be node objects (in the
* native data model supplied as input), or Java objects representing the XPath
* atomic values in the actual result: String for an xs:string, Double for a xs:double,
* Long for an xs:integer, and so on. (For safety, cast the values to a type
* such as xs:string within the XPath expression).
* @throws XPathExpressionException if evaluation of the expression fails or if the
* result cannot be converted to the requested type.
*/
/*@Nullable*/
@Override
public Object evaluate(/*@Nullable*/ Object node, /*@NotNull*/ QName qName) throws XPathExpressionException {
Item contextItem;
JPConverter converter = JPConverter.allocate(node.getClass(), null, config);
GroundedValue val;
try {
val = converter.convert(node, new EarlyEvaluationContext(config));
} catch (XPathException e) {
throw new XPathExpressionException(
"Failure converting a node of class " + node.getClass().getName() +
": " + e.getMessage());
}
if (val.getLength() == 0) {
contextItem = null;
} else if (val.getLength() > 1) {
throw new XPathExpressionException(
"Supplied context item is a sequence of " + val.getLength() + " items");
} else {
val = val.head();
if (val instanceof NodeInfo) {
if (!((NodeInfo) val).getConfiguration().isCompatible(config)) {
throw new XPathExpressionException(
"Supplied node must be built using the same or a compatible Configuration");
}
if (((NodeInfo) val).getTreeInfo().isTyped() && !executable.isSchemaAware()) {
throw new XPathExpressionException(
"The expression was compiled to handled untyped data, but the input is typed");
}
}
contextItem = (Item)val;
}
XPathContextMajor context = new XPathContextMajor(contextItem, executable);
context.openStackFrame(stackFrameMap);
try {
if (qName.equals(XPathConstants.BOOLEAN)) {
return expression.makeElaborator().elaborateForBoolean().eval(context);
} else if (qName.equals(XPathConstants.STRING)) {
SequenceIterator iter = expression.iterate(context);
Item first = iter.next();
if (first == null) {
return "";
}
return first.getStringValue();
} else if (qName.equals(XPathConstants.NUMBER)) {
if (atomizer == null) {
atomizer = Atomizer.makeAtomizer(expression, null);
}
SequenceIterator iter = atomizer.iterate(context);
Item first = iter.next();
if (first == null) {
return Double.NaN;
}
if (first instanceof NumericValue) {
return ((NumericValue) first).getDoubleValue();
} else {
DoubleValue v = Number_1.convert((AtomicValue) first, getConfiguration());
return v.getDoubleValue();
}
} else if (qName.equals(XPathConstants.NODE)) {
SequenceIterator iter = expression.iterate(context);
Item first = iter.next();
if (first instanceof VirtualNode) {
return ((VirtualNode) first).getRealNode();
}
if (first == null || first instanceof NodeInfo) {
return first;
}
throw new XPathExpressionException("Expression result is not a node");
} else if (qName.equals(XPathConstants.NODESET)) {
context.openStackFrame(stackFrameMap);
SequenceIterator iter = expression.iterate(context);
GroundedValue extent = SequenceTool.toGroundedValue(iter);
PJConverter pj = PJConverter.allocateNodeListCreator(config, node);
return pj.convert(extent, Object.class, context);
} else {
throw new IllegalArgumentException("qName: Unknown type for expected result");
}
} catch (XPathException e) {
throw new XPathExpressionException(e);
}
}
/**
* Evaluate the expression to return a string value
*
* @param node The context node: generalized in Saxon to allow any XDM item to act as the context item.
* The types of values accepted, and the conversions applied, are described in the Saxon
* documentation.
* Contrary to the interface specification, Saxon does not supply an empty
* document when the value is null. This is because XPath 2.0 allows the context
* item to be "absent" (null). So Saxon executes the XPath expression with the
* context item undefined.
* @return the results of the expression, converted to a String
* @throws XPathExpressionException if evaluation fails
*/
/*@NotNull*/
@Override
public String evaluate(Object node) throws XPathExpressionException {
return (String) evaluate(node, XPathConstants.STRING);
}
/**
* Evaluate the XPath expression against an input source to obtain a result of a specified type
*
* @param inputSource The input source document against which the expression is evaluated.
* If any error occurs reading or parsing this document, the error is notified
* to the {@link ErrorListener} registered with the {@link Configuration},
* and also causes an exception to be thrown.
* (Note that there is no caching. This will be parsed, and
* the parsed result will be discarded.)
* If the supplied value is null then (contrary to the JAXP specifications), the XPath expression
* is evaluated with the context item undefined.
* @param qName The type required, identified by a constant in {@link XPathConstants}
* @return the result of the evaluation, as a Java object of the appropriate type:
* see {@link #evaluate(Object, javax.xml.namespace.QName)}
* @throws XPathExpressionException if an error is detected
*/
/*@Nullable*/
@Override
public Object evaluate(/*@Nullable*/ InputSource inputSource, /*@Nullable*/ QName qName) throws XPathExpressionException {
if (qName == null) {
throw new NullPointerException("qName");
}
try {
NodeInfo doc = null;
if (inputSource != null) {
doc = config.buildDocumentTree(new SAXSource(inputSource)).getRootNode();
}
return evaluate(doc, qName);
} catch (XPathException e) {
throw new XPathExpressionException(e);
}
}
/**
* Evaluate the XPath expression against an input source to obtain a string result.
*
* @param inputSource The input source document against which the expression is evaluated.
* If any error occurs reading or parsing this document, the error is notified
* to the {@link ErrorListener} registered with the {@link Configuration},
* and also causes an exception to be thrown.
* (Note that there is no caching. This will be parsed, and
* the parsed result will be discarded.)
* If the supplied value is null then (contrary to the JAXP specifications), the XPath expression
* is evaluated with the context item undefined.
* @return the result of the evaluation, converted to a String
* @throws XPathExpressionException in the event of an XPath dynamic error
* @throws NullPointerException If inputSource is null.
*/
/*@NotNull*/
@Override
public String evaluate(/*@Nullable*/ InputSource inputSource) throws XPathExpressionException {
if (inputSource == null) {
throw new NullPointerException("inputSource");
}
try {
NodeInfo doc = config.buildDocumentTree(new SAXSource(inputSource)).getRootNode();
return (String) evaluate(doc, XPathConstants.STRING);
} catch (XPathException e) {
throw new XPathExpressionException(e);
}
}
/**
* Low-level method to get the internal Saxon expression object. This exposes a wide range of
* internal methods that may be needed by specialized applications, and allows greater control
* over the dynamic context for evaluating the expression.
*
* @return the underlying Saxon expression object.
*/
public Expression getInternalExpression() {
return expression;
}
}