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org.milyn.cdr.xpath.SelectorStep Maven / Gradle / Ivy
/*
Milyn - Copyright (C) 2006 - 2010
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License (version 2.1) as published by the Free Software
Foundation.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU Lesser General Public License for more details:
http://www.gnu.org/licenses/lgpl.txt
*/
package org.milyn.cdr.xpath;
import org.milyn.delivery.sax.SAXElement;
import org.milyn.assertion.AssertArgument;
import org.milyn.cdr.SmooksResourceConfiguration;
import org.milyn.cdr.xpath.evaluators.PassThruEvaluator;
import org.milyn.cdr.xpath.evaluators.PredicatesEvaluatorBuilder;
import org.milyn.cdr.xpath.evaluators.XPathExpressionEvaluator;
import org.milyn.cdr.xpath.evaluators.PredicatesEvaluator;
import org.milyn.cdr.xpath.evaluators.logical.AbstractLogicalEvaluator;
import org.milyn.cdr.xpath.evaluators.value.TextValue;
import org.milyn.cdr.xpath.evaluators.equality.AbstractEqualityEvaluator;
import org.milyn.cdr.xpath.evaluators.equality.IndexEvaluator;
import org.milyn.xml.DomUtils;
import org.w3c.dom.Element;
import org.jaxen.expr.Step;
import org.jaxen.expr.NameStep;
import org.jaxen.saxpath.Axis;
import org.jaxen.saxpath.SAXPathException;
import javax.xml.namespace.QName;
import javax.xml.XMLConstants;
import java.util.Properties;
import java.util.List;
import javassist.NotFoundException;
import javassist.CannotCompileException;
/**
* XPath Expression Evaluator.
*
* Implemenations evaluate a single step in an XPath expression.
*
* @author [email protected]
* Allows asssociation of an attribute step. XPath expressions can have the
* form "xxx/@abc", where the attribute "abc" is on the element "xxx".
*
* @param xpathExpression The XPath expression of which the {@link Step} is a
* part.
* @param step The XPath {@link Step}.
* @param attributeStep The Attribute Step.
* @throws SAXPathException Error constructing the selector step.
*/
public SelectorStep(String xpathExpression, Step step, Step attributeStep) throws SAXPathException {
this(xpathExpression, step);
AssertArgument.isNotNull(attributeStep, "attributeStep");
if(attributeStep.getAxis() != Axis.ATTRIBUTE) {
throw new IllegalArgumentException("Unexpected 'attributeStep' arg '" + attributeStep.getText() + "'. Must be an ATTRIBUTE Axis step.");
}
setAttributeStep(attributeStep);
initFlags();
}
/**
* Public constructor.
* @param xpathExpression The XPath expression of which the {@link Step} is a
* part.
* @param targetElementName The target element name associated with this selector step.
*/
public SelectorStep(String xpathExpression, String targetElementName) {
AssertArgument.isNotNull(xpathExpression, "xpathExpression");
AssertArgument.isNotNull(targetElementName, "targetElementName");
this.xpathExpression = xpathExpression;
targetElement = new QName(targetElementName);
initFlags();
}
/**
* Public constructor.
* @param xpathExpression The XPath expression of which the {@link Step} is a
* part.
* @param targetElementName The target element name associated with this selector step.
* @param targetAttributeName The target attribute name associated with this selector step.
*/
public SelectorStep(String xpathExpression, String targetElementName, String targetAttributeName) {
this(xpathExpression, targetElementName);
AssertArgument.isNotNull(targetAttributeName, "targetAttributeName");
targetAttribute = new QName(targetAttributeName);
}
public Step getAttributeStep() {
return attributeStep;
}
public void setAttributeStep(Step attributeStep) {
this.attributeStep = attributeStep;
try {
targetAttribute = toQName(attributeStep, null);
} catch (SAXPathException e) {
throw new IllegalStateException("Unexpected SAXPathException setting attribute SelectorStep.", e);
}
}
@Override
public SelectorStep clone() {
SelectorStep clone;
try {
clone = new SelectorStep(xpathExpression);
} catch (SAXPathException e) {
throw new IllegalStateException("Unexpected SAXPathException cloning SelectorStep.", e);
}
clone.xpathExpression = xpathExpression;
clone.step = step;
clone.attributeStep = attributeStep;
clone.isRooted = isRooted;
clone.isStar = isStar;
clone.isStarStar = isStarStar;
clone.targetElement = targetElement;
clone.targetAttribute = targetAttribute;
clone.predicatesEvaluator = predicatesEvaluator;
return clone;
}
/**
* Initialize the step flags.
*/
private void initFlags() {
isStar = targetElement.getLocalPart().equals("*");
isStarStar = targetElement.getLocalPart().equals("**");
setRooted(targetElement.getLocalPart().equals(SmooksResourceConfiguration.DOCUMENT_FRAGMENT_SELECTOR));
}
/**
* Get the XPath selector expression of which this SelectorStep instance is a part.
* @return The XPath selector expression of which this SelectorStep instance is a part.
*/
public String getXPathExpression() {
return xpathExpression;
}
public QName getTargetElement() {
return targetElement;
}
public QName getTargetAttribute() {
return targetAttribute;
}
public XPathExpressionEvaluator getPredicatesEvaluator() {
return predicatesEvaluator;
}
public boolean isRooted() {
return isRooted;
}
public void setRooted(boolean rooted) {
isRooted = rooted;
// Can't be rooted and **...
if(isStarStar) {
isRooted = false;
}
}
public boolean isStar() {
return isStar;
}
public boolean isStarStar() {
return isStarStar;
}
public void buildPredicatesEvaluator(Properties namespaces) throws SAXPathException, NotFoundException, CannotCompileException, IllegalAccessException, InstantiationException {
AssertArgument.isNotNull(namespaces, "namespaces");
if(predicatesEvaluator != null) {
return;
}
if(step != null) {
PredicatesEvaluatorBuilder builder = new PredicatesEvaluatorBuilder(step, attributeStep, this, namespaces);
try {
predicatesEvaluator = builder.build();
} catch (SAXPathException e) {
throw new SAXPathException("Error processing XPath selector expression '" + xpathExpression + "'.", e);
}
// And update the QNames again now that we have the namespaces...
targetElement = toQName(step, builder);
if(attributeStep != null) {
targetAttribute = toQName(attributeStep, builder);
}
} else {
predicatesEvaluator = PassThruEvaluator.INSTANCE;
}
}
public boolean isTargetedAtElement(SAXElement element) {
QName qname = element.getName();
if(isStar || isStarStar) {
return true;
}
if(!qname.getLocalPart().equalsIgnoreCase(targetElement.getLocalPart())) {
return false;
} else if (!isTargetedAtNamespace(qname.getNamespaceURI())) {
return false;
}
return true;
}
public boolean isTargetedAtElement(Element element) {
String elementName = DomUtils.getName(element);
if(isStar || isStarStar) {
return true;
}
if(!elementName.equalsIgnoreCase(targetElement.getLocalPart())) {
return false;
} else if (!isTargetedAtNamespace(element.getNamespaceURI())) {
return false;
}
return true;
}
/**
* Is this StepSelector instance targeted at the specified namespace.
*
* If the StepSelector namespace is null, it automatically matches and no
* comparison is made against the supplied namespace.
*
* @param namespace The namespace to be tested.
* @return True if the target namespace matches (or is null), otherwise false.
*/
public boolean isTargetedAtNamespace(String namespace) {
String targetNS = targetElement.getNamespaceURI();
// If the target NS is null, we match, no matter what the specified namespace...
if(targetNS == null || targetNS == XMLConstants.NULL_NS_URI) {
return true;
}
return targetNS.equals(namespace);
}
/**
* Does this step require access to the element text content.
*
* Does this step include a 'text()' predicate at any level.
*
* @return True if the step requires access to the element's text content, otherwise false.
*/
public boolean accessesText() {
XPathExpressionEvaluator evaluator = getPredicatesEvaluator();
if(evaluator == null) {
return false;
}
if(accessesText(evaluator)) {
return true;
}
return false;
}
/**
* Does the supplied {@link XPathExpressionEvaluator} access the element text content.
* @return True if the supplied {@link XPathExpressionEvaluator} accesses the element text content,
* otherwise false.
*/
private boolean accessesText(XPathExpressionEvaluator evaluator) {
if(evaluator instanceof AbstractEqualityEvaluator) {
if(((AbstractEqualityEvaluator)evaluator).getLhs() instanceof TextValue) {
return true;
} else if(((AbstractEqualityEvaluator)evaluator).getRhs() instanceof TextValue) {
return true;
}
} else if(evaluator instanceof AbstractLogicalEvaluator) {
if(accessesText(((AbstractLogicalEvaluator)evaluator).getLhs())) {
return true;
} else if(accessesText(((AbstractLogicalEvaluator)evaluator).getRhs())) {
return true;
}
} else if(evaluator instanceof PredicatesEvaluator) {
List evaluators = ((PredicatesEvaluator) evaluator).getEvaluators();
for(XPathExpressionEvaluator pEvaluator : evaluators) {
if(accessesText(pEvaluator)) {
return true;
}
}
}
return false;
}
public void getEvaluators(Class evaluatorClass, List evaluators) {
getEvaluators(getPredicatesEvaluator(), evaluatorClass, (List) evaluators);
}
private void getEvaluators(XPathExpressionEvaluator evaluator, Class evaluatorClass, List evaluators) {
if(evaluator.getClass() == evaluatorClass) {
evaluators.add(evaluator);
}
if(evaluator instanceof AbstractLogicalEvaluator) {
getEvaluators(((AbstractLogicalEvaluator)evaluator).getLhs(), evaluatorClass, evaluators);
getEvaluators(((AbstractLogicalEvaluator)evaluator).getRhs(), evaluatorClass, evaluators);
} else if(evaluator instanceof PredicatesEvaluator) {
List subEvaluators = ((PredicatesEvaluator) evaluator).getEvaluators();
for(XPathExpressionEvaluator pEvaluator : subEvaluators) {
getEvaluators(pEvaluator, evaluatorClass, evaluators);
}
}
}
private QName toQName(Step step, PredicatesEvaluatorBuilder evaluatorCompiler) throws SAXPathException {
String nsPrefix = ((NameStep) step).getPrefix();
String localPart = ((NameStep) step).getLocalName();
if(nsPrefix != null && !nsPrefix.trim().equals("")) {
if(evaluatorCompiler != null) {
return new QName(evaluatorCompiler.getNamespace(nsPrefix), localPart, nsPrefix);
} else {
// Will need to update the namespace later... when we have the
// namespace prefix-to-uri mappings...
return new QName(null, localPart, nsPrefix);
}
} else {
return new QName(localPart);
}
}
public String toString() {
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append(getTargetElement());
if(targetAttribute != null) {
stringBuilder.append("{@" + targetAttribute + "}");
}
XPathExpressionEvaluator evaluator = getPredicatesEvaluator();
if(evaluator != null) {
stringBuilder.append(evaluator);
}
return stringBuilder.toString();
}
/**
* Set the namespaces on the specified set of selector steps.
* @param steps The selector steps.
* @param namespaces The set of selector steps to be updated.
* @return The set of selector steps (as passed in the 'steps' argument).
* @throws org.jaxen.saxpath.SAXPathException Error setting namespaces
*/
public static SelectorStep[] setNamespaces(SelectorStep[] steps, Properties namespaces) throws SAXPathException {
AssertArgument.isNotNull(steps, "steps");
AssertArgument.isNotNull(namespaces, "namespaces");
for(int i = 0; i < steps.length; i++) {
SelectorStep step = steps[i];
try {
step.buildPredicatesEvaluator(namespaces);
} catch (SAXPathException e) {
throw e;
} catch (Exception e) {
throw new SAXPathException("Error compiling PredicatesEvaluator.", e);
}
//
if(i < steps.length - 1 && step.accessesText()) {
throw new SAXPathException("Unsupported XPath selector expression '" + step.getXPathExpression() + "'. XPath 'text()' tokens are only supported in the last step.");
}
}
return steps;
}
/**
* Is this selector step a hashed attribute selector step.
* @return True if the selector step is a hashed attribute selector, otherwise false.
*/
public boolean isHashedAttribute() {
return false;
}
}
