org.apache.xpath.jaxp.XPathExpressionImpl Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
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*
* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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* limitations under the License.
*/
// $Id: XPathExpressionImpl.java 1225277 2011-12-28 18:50:56Z mrglavas $
package org.apache.xpath.jaxp;
import javax.xml.namespace.QName;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFunctionResolver;
import javax.xml.xpath.XPathVariableResolver;
import org.apache.xalan.res.XSLMessages;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.traversal.NodeIterator;
import org.xml.sax.InputSource;
/**
* The XPathExpression interface encapsulates a (compiled) XPath expression.
*
* @version $Revision: 1225277 $
* @author Ramesh Mandava
*/
public class XPathExpressionImpl implements javax.xml.xpath.XPathExpression{
private XPathFunctionResolver functionResolver;
private XPathVariableResolver variableResolver;
private JAXPPrefixResolver prefixResolver;
private org.apache.xpath.XPath xpath;
// By default Extension Functions are allowed in XPath Expressions. If
// Secure Processing Feature is set on XPathFactory then the invocation of
// extensions function need to throw XPathFunctionException
private boolean featureSecureProcessing = false;
/** Protected constructor to prevent direct instantiation; use compile()
* from the context.
*/
protected XPathExpressionImpl() { };
protected XPathExpressionImpl(org.apache.xpath.XPath xpath,
JAXPPrefixResolver prefixResolver,
XPathFunctionResolver functionResolver,
XPathVariableResolver variableResolver ) {
this.xpath = xpath;
this.prefixResolver = prefixResolver;
this.functionResolver = functionResolver;
this.variableResolver = variableResolver;
this.featureSecureProcessing = false;
};
protected XPathExpressionImpl(org.apache.xpath.XPath xpath,
JAXPPrefixResolver prefixResolver,
XPathFunctionResolver functionResolver,
XPathVariableResolver variableResolver,
boolean featureSecureProcessing ) {
this.xpath = xpath;
this.prefixResolver = prefixResolver;
this.functionResolver = functionResolver;
this.variableResolver = variableResolver;
this.featureSecureProcessing = featureSecureProcessing;
};
public void setXPath (org.apache.xpath.XPath xpath ) {
this.xpath = xpath;
}
public Object eval(Object item, QName returnType)
throws javax.xml.transform.TransformerException {
XObject resultObject = eval ( item );
return getResultAsType( resultObject, returnType );
}
private XObject eval ( Object contextItem )
throws javax.xml.transform.TransformerException {
org.apache.xpath.XPathContext xpathSupport = null;
// Create an XPathContext that doesn't support pushing and popping of
// variable resolution scopes. Sufficient for simple XPath 1.0
// expressions.
if ( functionResolver != null ) {
JAXPExtensionsProvider jep = new JAXPExtensionsProvider(
functionResolver, featureSecureProcessing );
xpathSupport = new org.apache.xpath.XPathContext(jep, false);
} else {
xpathSupport = new org.apache.xpath.XPathContext(false);
}
xpathSupport.setVarStack(new JAXPVariableStack(variableResolver));
XObject xobj = null;
Node contextNode = (Node)contextItem;
// We always need to have a ContextNode with Xalan XPath implementation
// To allow simple expression evaluation like 1+1 we are setting
// dummy Document as Context Node
if ( contextNode == null ) {
contextNode = getDummyDocument();
}
xobj = xpath.execute(xpathSupport, contextNode, prefixResolver );
return xobj;
}
/**
* Evaluate the compiled XPath expression in the specified context and
* return the result as the specified type.
*
* See "Evaluation of XPath Expressions" section of JAXP 1.3 spec
* for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* If returnType is not one of the types defined
* in {@link XPathConstants},
* then an IllegalArgumentException is thrown.
*
* If a null value is provided for
* item, an empty document will be used for the
* context.
* If returnType is null, then a
* NullPointerException is thrown.
*
* @param item The starting context (node or node list, for example).
* @param returnType The desired return type.
*
* @return The Object that is the result of evaluating the
* expression and converting the result to
* returnType.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If returnType is not one
* of the types defined in {@link XPathConstants}.
* @throws NullPointerException If returnType is
* null.
*/
public Object evaluate(Object item, QName returnType)
throws XPathExpressionException {
//Validating parameters to enforce constraints defined by JAXP spec
if ( returnType == null ) {
//Throwing NullPointerException as defined in spec
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
new Object[] {"returnType"} );
throw new NullPointerException( fmsg );
}
// Checking if requested returnType is supported. returnType need to be
// defined in XPathConstants
if ( !isSupported ( returnType ) ) {
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
new Object[] { returnType.toString() } );
throw new IllegalArgumentException ( fmsg );
}
try {
return eval( item, returnType);
} catch ( java.lang.NullPointerException npe ) {
// If VariableResolver returns null Or if we get
// NullPointerException at this stage for some other reason
// then we have to reurn XPathException
throw new XPathExpressionException ( npe );
} catch ( javax.xml.transform.TransformerException te ) {
Throwable nestedException = te.getException();
if ( nestedException instanceof javax.xml.xpath.XPathFunctionException ) {
throw (javax.xml.xpath.XPathFunctionException)nestedException;
} else {
// For any other exceptions we need to throw
// XPathExpressionException ( as per spec )
throw new XPathExpressionException( te);
}
}
}
/**
* Evaluate the compiled XPath expression in the specified context and
* return the result as a String.
*
* This method calls {@link #evaluate(Object item, QName returnType)}
* with a returnType of
* {@link XPathConstants#STRING}.
*
* See "Evaluation of XPath Expressions" section of JAXP 1.3 spec
* for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* If a null value is provided for
* item, an empty document will be used for the
* context.
*
* @param item The starting context (node or node list, for example).
*
* @return The String that is the result of evaluating the
* expression and converting the result to a
* String.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
*/
public String evaluate(Object item)
throws XPathExpressionException {
return (String)this.evaluate( item, XPathConstants.STRING );
}
static DocumentBuilderFactory dbf = null;
static DocumentBuilder db = null;
static Document d = null;
/**
*
Evaluate the compiled XPath expression in the context of the
* specified InputSource and return the result as the
* specified type.
*
* This method builds a data model for the {@link InputSource} and calls
* {@link #evaluate(Object item, QName returnType)} on the resulting
* document object.
*
* See "Evaluation of XPath Expressions" section of JAXP 1.3 spec
* for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* If returnType is not one of the types defined in
* {@link XPathConstants},
* then an IllegalArgumentException is thrown.
*
*If source or returnType is null,
* then a NullPointerException is thrown.
*
* @param source The InputSource of the document to evaluate
* over.
* @param returnType The desired return type.
*
* @return The Object that is the result of evaluating the
* expression and converting the result to
* returnType.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If returnType is not one
* of the types defined in {@link XPathConstants}.
* @throws NullPointerException If source or
* returnType is null.
*/
public Object evaluate(InputSource source, QName returnType)
throws XPathExpressionException {
if ( ( source == null ) || ( returnType == null ) ) {
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_SOURCE_RETURN_TYPE_CANNOT_BE_NULL,
null );
throw new NullPointerException ( fmsg );
}
// Checking if requested returnType is supported. returnType need to be
// defined in XPathConstants
if ( !isSupported ( returnType ) ) {
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
new Object[] { returnType.toString() } );
throw new IllegalArgumentException ( fmsg );
}
try {
if ( dbf == null ) {
dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware( true );
dbf.setValidating( false );
}
db = dbf.newDocumentBuilder();
Document document = db.parse( source );
return eval( document, returnType );
} catch ( Exception e ) {
throw new XPathExpressionException ( e );
}
}
/**
* Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as a
* String.
*
* This method calls {@link #evaluate(InputSource source, QName returnType)} with a returnType of
* {@link XPathConstants#STRING}.
*
* See "Evaluation of XPath Expressions" section of JAXP 1.3 spec
* for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* If source is null, then a NullPointerException is thrown.
*
* @param source The InputSource of the document to evaluate over.
*
* @return The String that is the result of evaluating the expression and converting the result to a
* String.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws NullPointerException If source is null.
*/
public String evaluate(InputSource source)
throws XPathExpressionException {
return (String)this.evaluate( source, XPathConstants.STRING );
}
private boolean isSupported( QName returnType ) {
// XPathConstants.STRING
if ( ( returnType.equals( XPathConstants.STRING ) ) ||
( returnType.equals( XPathConstants.NUMBER ) ) ||
( returnType.equals( XPathConstants.BOOLEAN ) ) ||
( returnType.equals( XPathConstants.NODE ) ) ||
( returnType.equals( XPathConstants.NODESET ) ) ) {
return true;
}
return false;
}
private Object getResultAsType( XObject resultObject, QName returnType )
throws javax.xml.transform.TransformerException {
// XPathConstants.STRING
if ( returnType.equals( XPathConstants.STRING ) ) {
return resultObject.str();
}
// XPathConstants.NUMBER
if ( returnType.equals( XPathConstants.NUMBER ) ) {
return new Double ( resultObject.num());
}
// XPathConstants.BOOLEAN
if ( returnType.equals( XPathConstants.BOOLEAN ) ) {
return resultObject.bool() ? Boolean.TRUE : Boolean.FALSE;
}
// XPathConstants.NODESET ---ORdered, UNOrdered???
if ( returnType.equals( XPathConstants.NODESET ) ) {
return resultObject.nodelist();
}
// XPathConstants.NODE
if ( returnType.equals( XPathConstants.NODE ) ) {
NodeIterator ni = resultObject.nodeset();
//Return the first node, or null
return ni.nextNode();
}
// If isSupported check is already done then the execution path
// shouldn't come here. Being defensive
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
new Object[] { returnType.toString()});
throw new IllegalArgumentException ( fmsg );
}
private static Document getDummyDocument( ) {
try {
if ( dbf == null ) {
dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware( true );
dbf.setValidating( false );
}
db = dbf.newDocumentBuilder();
DOMImplementation dim = db.getDOMImplementation();
d = dim.createDocument("http://java.sun.com/jaxp/xpath",
"dummyroot", null);
return d;
} catch ( Exception e ) {
e.printStackTrace();
}
return null;
}
}