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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.om.Item;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.sxpath.XPathDynamicContext;
import net.sf.saxon.sxpath.XPathExpression;
import net.sf.saxon.sxpath.XPathVariable;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.SequenceExtent;
import javax.xml.transform.URIResolver;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
* An XPathSelector represents a compiled and loaded XPath expression ready for execution.
* The XPathSelector holds details of the dynamic evaluation context for the XPath expression.
*/
@SuppressWarnings({"ForeachStatement"})
public class XPathSelector implements Iterable {
private XPathExpression exp;
private XPathDynamicContext dynamicContext;
private List declaredVariables;
// protected constructor
protected XPathSelector(XPathExpression exp,
ArrayList declaredVariables) {
this.exp = exp;
this.declaredVariables = declaredVariables;
dynamicContext = exp.createDynamicContext();
}
/**
* Set the context item for evaluating the XPath expression.
* This may be either a node or an atomic value. Most commonly it will be a document node,
* which might be constructed using the {@link DocumentBuilder#build} method.
*
* @param item The context item for evaluating the expression. Must not be null.
* @throws SaxonApiException if an error occurs, for example because the type
* of item supplied does not match the required item type
*
*/
public void setContextItem(XdmItem item) throws SaxonApiException {
if (item == null) {
throw new NullPointerException("contextItem");
}
try {
dynamicContext.setContextItem((Item)item.getUnderlyingValue());
} catch (XPathException e) {
throw new SaxonApiException(e);
}
}
/**
* Get the context item used for evaluating the XPath expression.
* This may be either a node or an atomic value. Most commonly it will be a document node,
* which might be constructed using the Build method of the DocumentBuilder object.
*
* @return The context item for evaluating the expression, or null if no context item
* has been set.
*/
public XdmItem getContextItem() {
return XdmItem.wrapItem(dynamicContext.getContextItem());
}
/**
* Set the value of a variable
*
* @param name The name of the variable. This must match the name of a variable
* that was declared to the XPathCompiler. No error occurs if the expression does not
* actually reference a variable with this name.
* @param value The value to be given to the variable.
* @throws SaxonApiException if the variable has not been declared or if the type of the value
* supplied does not conform to the required type that was specified when the variable was declared
*/
public void setVariable(QName name, XdmValue value) throws SaxonApiException {
XPathVariable var = null;
StructuredQName qn = name.getStructuredQName();
for (XPathVariable v : declaredVariables) {
if (v.getVariableQName().equals(qn)) {
var = v;
break;
}
}
if (var == null) {
throw new SaxonApiException(
new XPathException("Variable has not been declared: " + name));
}
try {
dynamicContext.setVariable(var, value.getUnderlyingValue());
} catch (XPathException e) {
throw new SaxonApiException(e);
}
}
/**
* Set an object that will be used to resolve URIs used in
* fn:doc() and related functions.
*
* @param resolver An object that implements the URIResolver interface, or null.
* @since 9.4
*/
public void setURIResolver(URIResolver resolver) {
dynamicContext.setURIResolver(resolver);
}
/**
* Get the URI resolver.
*
* @return the user-supplied URI resolver if there is one, or the
* system-defined one otherwise
* @since 9.4
*/
public URIResolver getURIResolver() {
return dynamicContext.getURIResolver();
}
/**
* Evaluate the expression, returning the result as an XdmValue (that is,
* a sequence of nodes and/or atomic values).
*
* Note: Although a singleton result may be represented as an XdmItem, there is
* no guarantee that this will always be the case. If you know that the expression will return at
* most one node or atomic value, it is best to use the evaluateSingle method, which
* does guarantee that an XdmItem (or null) will be returned.
*
* @return An XdmValue representing the results of the expression.
* @throws SaxonApiException if a dynamic error occurs during the expression evaluation.
*/
public XdmValue evaluate() throws SaxonApiException {
Sequence value;
try {
value = SequenceExtent.makeSequenceExtent(exp.iterate(dynamicContext));
} catch (XPathException e) {
throw new SaxonApiException(e);
}
return XdmValue.wrap(value);
}
/**
* Evaluate the XPath expression, returning the result as an XdmItem (that is,
* a single node or atomic value).
*
* @return an XdmItem representing the result of the expression, or null if the expression
* returns an empty sequence. If the expression returns a sequence of more than one item,
* any items after the first are ignored.
* @throws SaxonApiException if a dynamic error occurs during the expression evaluation.
*/
public XdmItem evaluateSingle() throws SaxonApiException {
try {
Item i = exp.evaluateSingle(dynamicContext);
if (i == null) {
return null;
}
return (XdmItem) XdmValue.wrap(i);
} catch (XPathException e) {
throw new SaxonApiException(e);
}
}
/**
* Evaluate the expression, returning the result as an Iterator (that is,
* an iterator over a sequence of nodes and/or atomic values).
*
* Because an XPathSelector is an {@link Iterable}, it is possible to
* iterate over the result using a Java 5 "for each" expression, for example:
*
*
* XPathCompiler compiler = processor.newXPathCompiler();
* XPathSelector seq = compiler.compile("1 to 20").load();
* for (XdmItem item : seq) {
* System.err.println(item);
* }
*
*
* @return An iterator over the sequence that represents the results of the expression.
* Each object in this sequence will be an instance of XdmItem. Note
* that the expression may be evaluated lazily, which means that a successful response
* from this method does not imply that the expression has executed successfully: failures
* may be reported later while retrieving items from the iterator.
* @throws SaxonApiUncheckedException
* if a dynamic error occurs during XPath evaluation that
* can be detected at this point. It is also possible that an SaxonApiUncheckedException will
* be thrown by the hasNext() method of the returned iterator.
*/
public Iterator iterator() throws SaxonApiUncheckedException {
try {
return new XdmSequenceIterator(exp.iterate(dynamicContext));
} catch (XPathException e) {
throw new SaxonApiUncheckedException(e);
}
}
/**
* Evaluate the XPath expression, returning the effective boolean value of the result.
*
* @return a boolean representing the effective boolean value of the result of evaluating
* the expression, as defined by the rules for the fn:boolean() function.
* @throws SaxonApiException if a dynamic error occurs during the expression evaluation, or if the result
* of the expression is a value whose effective boolean value is not defined (for example, a date or a
* sequence of three integers)
* @since 9.1
*/
public boolean effectiveBooleanValue() throws SaxonApiException {
try {
return exp.effectiveBooleanValue(dynamicContext);
} catch (XPathException e) {
throw new SaxonApiException(e);
}
}
/**
* Get the underlying dynamic context object. This provides an escape hatch to the underlying
* implementation classes, which contain methods that may change from one release to another.
*
* @return the underlying object representing the dynamic context for query execution
*/
public XPathDynamicContext getUnderlyingXPathContext() {
return dynamicContext;
}
}