org.milyn.cdr.xpath.SelectorStepBuilder 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.jaxen.expr.*;
import org.jaxen.saxpath.SAXPathException;
import org.jaxen.saxpath.XPathReader;
import org.jaxen.saxpath.Axis;
import org.jaxen.saxpath.helpers.XPathReaderFactory;
import org.jaxen.JaxenHandler;
import org.milyn.assertion.AssertArgument;
import org.milyn.cdr.SmooksResourceConfiguration;
import javax.xml.namespace.QName;
import java.util.List;
import java.util.ArrayList;
import java.util.Properties;
/**
* {@link SelectorStep} Builder class.
*
* @author [email protected]
*/
public class SelectorStepBuilder {
private static SelectorStep[] SELECTOR_NONE_STEP;
static {
try {
SELECTOR_NONE_STEP = _buildSteps(SmooksResourceConfiguration.SELECTOR_NONE);
} catch (SAXPathException e) {
throw new IllegalStateException("Unexpected exception while constructing the 'none' SelectorStep array.");
}
}
/**
* Construct a set of selector steps from the specified selector (ala XPath expresssion steps).
*
* This process does not configure the namespaces on the steps. The {@link SelectorStep#setNamespaces(SelectorStep[],java.util.Properties)}
* method needs to be called to configure the namespaces.
*
* @param selectorExpression The selector expression.
* @return The set of selector steps.
* @throws SAXPathException Error parsing expression.
*/
public static SelectorStep[] buildSteps(String selectorExpression) throws SAXPathException {
if(selectorExpression == SmooksResourceConfiguration.SELECTOR_NONE) {
return SELECTOR_NONE_STEP;
}
return _buildSteps(selectorExpression);
}
/**
* Construct a set of selector steps from the specified selector (ala XPath expresssion steps).
*
* This process does not configure the namespaces on the steps. The {@link SelectorStep#setNamespaces(SelectorStep[],java.util.Properties)}
* method needs to be called to configure the namespaces.
*
* @param selectorExpression The selector expression.
* @return The set of selector steps.
* @throws SAXPathException Error parsing expression.
*/
private static SelectorStep[] _buildSteps(String selectorExpression) throws SAXPathException {
AssertArgument.isNotNull(selectorExpression, "selectorExpression");
String xpathExpression = toXPathExpression(selectorExpression);
XPathReader reader = XPathReaderFactory.createReader();
JaxenHandler handler = new JaxenHandler();
List selectorSteps = new ArrayList();
boolean isRooted = false;
boolean endsStarStar = false;
if(xpathExpression.startsWith("/")) {
isRooted = true;
}
if(xpathExpression.endsWith("//")) {
endsStarStar = true;
xpathExpression = xpathExpression.substring(0, xpathExpression.length() - 2);
}
if(xpathExpression.trim().length() > 0) {
reader.setXPathHandler(handler);
reader.parse(xpathExpression);
XPathExpr xpath = handler.getXPathExpr();
Expr expr = xpath.getRootExpr();
if (!(expr instanceof LocationPath)) {
throw new SAXPathException("Invalid XPath expression '" + xpathExpression + "'. Selector must be a LocationPath expression. Is '" + expr.getText() + "'.");
}
LocationPath path = (LocationPath) expr;
List steps = path.getSteps();
for (int i = 0; i < steps.size(); i++) {
Step step = steps.get(i);
try {
if(step.getAxis() == Axis.ATTRIBUTE && i < steps.size() - 1) {
// Attribute steps are only supported as the last step...
throw new SAXPathException("Attribute axis steps are only supported at the end of the expression. '" + step.getText() + "' is not at the end.");
} else if(step.getAxis() == Axis.DESCENDANT_OR_SELF) {
selectorSteps.add(new SelectorStep(xpathExpression, "**"));
} else if(step.getAxis() != Axis.CHILD && step.getAxis() != Axis.ATTRIBUTE) {
throw new SAXPathException("XPath step '" + step.getText() + "' not supported.");
} else {
if(i == steps.size() - 2) {
Step nextStep = steps.get(i + 1);
if(nextStep.getAxis() == Axis.ATTRIBUTE) {
selectorSteps.add(new SelectorStep(xpathExpression, step, nextStep));
// We end here. The next step is the last step and we've merged it into
// the last evaluator...
break;
} else {
selectorSteps.add(new SelectorStep(xpathExpression, step));
}
} else {
selectorSteps.add(new SelectorStep(xpathExpression, step));
}
}
} catch (SAXPathException e) {
throw new SAXPathException("Error processing XPath selector expression '" + xpathExpression + "'.", e);
} catch (Exception e) {
throw new SAXPathException("Error building step evaluator.", e);
}
}
}
if(isRooted) {
if(selectorSteps.isEmpty()) {
selectorSteps.add(new SelectorStep(xpathExpression, SmooksResourceConfiguration.DOCUMENT_FRAGMENT_SELECTOR));
} else {
selectorSteps.get(0).setRooted(true);
}
}
if(endsStarStar) {
selectorSteps.add(new SelectorStep(xpathExpression, "**"));
}
return selectorSteps.toArray(new SelectorStep[selectorSteps.size()]);
}
/**
* Construct a set of selector steps from the specified selector (ala XPath expresssion steps).
*
* @param selectorExpression The selector expression.
* @param namespaces The namespace prefix-to-uri mappings.
* @return The set of selector steps.
* @throws SAXPathException Error parsing expression.
*/
public static SelectorStep[] buildSteps(String selectorExpression, Properties namespaces) throws SAXPathException {
SelectorStep[] steps = buildSteps(selectorExpression);
return SelectorStep.setNamespaces(steps, namespaces);
}
/**
* Create a print friendly representation of the set of selector steps.
* @param steps The selector steps.
* @return A print friendly representation of the set of selector steps.
*/
public static String toString(SelectorStep[] steps) {
AssertArgument.isNotNull(steps, "steps");
StringBuilder stringBuilder = new StringBuilder();
for(int i = 0; i < steps.length; i++) {
if(steps[i].isRooted()) {
stringBuilder.append("/");
} else if(i > 0) {
stringBuilder.append("/");
}
stringBuilder.append(steps[i]);
}
return stringBuilder.toString();
}
/**
* Normalize the selector expression to an XPath expression.
*
* Historically, the Smooks selectors support some tokens not supported by the XPath spec.
* This method normalizes a selector expression to be a valid XPath expression.
*
* @param selectorExpression A selector expression.
* @return An XPath expression.
*/
private static String toXPathExpression(final String selectorExpression) {
// Need to remove all space characters where they don't
// exist inside squaere brackets...
StringBuilder xpathExpressionBuilder = new StringBuilder();
boolean normalize = true;
for(int i = 0; i < selectorExpression.length(); i++) {
char character = selectorExpression.charAt(i);
if(character == '[') {
normalize = false;
} else if(character == ']') {
normalize = true;
} else if(character == ' ' && normalize) {
if(xpathExpressionBuilder.charAt(xpathExpressionBuilder.length() - 1) != '/') {
xpathExpressionBuilder.append('/');
}
continue;
}
xpathExpressionBuilder.append(character);
}
String xpathExpression = xpathExpressionBuilder.toString();
// Handle the #document token. Just replace it with a leading slash..
xpathExpression = xpathExpression.replace(SmooksResourceConfiguration.LEGACY_DOCUMENT_FRAGMENT_SELECTOR, SmooksResourceConfiguration.DOCUMENT_FRAGMENT_SELECTOR);
if(xpathExpression.equals(SmooksResourceConfiguration.DOCUMENT_FRAGMENT_SELECTOR)) {
xpathExpression = "/";
} if(xpathExpression.startsWith(SmooksResourceConfiguration.DOCUMENT_FRAGMENT_SELECTOR + "/")) {
xpathExpression = xpathExpression.substring(SmooksResourceConfiguration.DOCUMENT_FRAGMENT_SELECTOR.length());
}
// Replace the legacy ** token with the XPath descendant-or-self axis token...
xpathExpression = xpathExpression.replace("/**/", "//");
xpathExpression = xpathExpression.replace("/**", "//");
xpathExpression = xpathExpression.replace("**/", "//");
return xpathExpression;
}
public static String[] toContextualSelector(SelectorStep[] selectorSteps) {
String targetAttribute = extractTargetAttribute(selectorSteps);
String[] contextualSelector;
if(targetAttribute != null) {
contextualSelector = new String[selectorSteps.length + 1];
contextualSelector[contextualSelector.length - 1] = "@" + targetAttribute;
} else {
contextualSelector = new String[selectorSteps.length];
}
for(int i = 0; i < selectorSteps.length; i++) {
contextualSelector[i] = selectorSteps[i].getTargetElement().getLocalPart();
}
return contextualSelector;
}
public static String extractTargetElement(SelectorStep[] selectorSteps) {
return selectorSteps[selectorSteps.length - 1].getTargetElement().getLocalPart();
}
public static String extractTargetAttribute(SelectorStep[] selectorSteps) {
QName targetAttribute = selectorSteps[selectorSteps.length - 1].getTargetAttribute();
if(targetAttribute == null) {
return null;
}
return targetAttribute.getLocalPart();
}
}