http://xml.apache.org/xalan-j/: Serializer to write out XML, HTML etc. as a stream of characters from an input DOM or from input SAX events. (The Apache Software Foundation) 
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 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * 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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// $Id: XPathImpl.java 1225280 2011-12-28 18:52:55Z mrglavas $

package org.apache.xpath.jaxp;

import javax.xml.namespace.QName;
import javax.xml.namespace.NamespaceContext;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFunctionResolver;
import javax.xml.xpath.XPathVariableResolver;
import javax.xml.xpath.XPathExpression;

import org.apache.xml.dtm.DTM;
import org.apache.xpath.*;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
import org.apache.xalan.res.XSLMessages;

import org.w3c.dom.Node;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.traversal.NodeIterator;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.parsers.*;

import java.io.IOException;


The XPathImpl class provides implementation for the methods defined  in
javax.xml.xpath.XPath interface. This provide simple access to the results
of an XPath expression.

Author: Ramesh Mandava
Version:$Revision: 1225280 $
/**
 * The XPathImpl class provides implementation for the methods defined  in
 * javax.xml.xpath.XPath interface. This provide simple access to the results
 * of an XPath expression.
 *
 *
 * @version $Revision: 1225280 $
 * @author  Ramesh Mandava
 */
public class XPathImpl implements javax.xml.xpath.XPath {

    // Private variables
    private XPathVariableResolver variableResolver;
    private XPathFunctionResolver functionResolver;
    private XPathVariableResolver origVariableResolver;
    private XPathFunctionResolver origFunctionResolver;
    private NamespaceContext namespaceContext=null;
    private JAXPPrefixResolver prefixResolver;
    // 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; 

    XPathImpl( XPathVariableResolver vr, XPathFunctionResolver fr ) {
        this.origVariableResolver = this.variableResolver = vr;
        this.origFunctionResolver = this.functionResolver = fr;
    }

    XPathImpl( XPathVariableResolver vr, XPathFunctionResolver fr, 
            boolean featureSecureProcessing ) {
        this.origVariableResolver = this.variableResolver = vr;
        this.origFunctionResolver = this.functionResolver = fr;
        this.featureSecureProcessing = featureSecureProcessing;
    }

    
Establishes a variable resolver.


Params:
  • resolver – Variable Resolver
/**
     * <p>Establishes a variable resolver.</p>
     *
     * @param resolver Variable Resolver
     */
    public void setXPathVariableResolver(XPathVariableResolver resolver) {
        if ( resolver == null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"XPathVariableResolver"} );
            throw new NullPointerException( fmsg );
        }
        this.variableResolver = resolver;
    }

    
Returns the current variable resolver.


Returns:Current variable resolver
/**
     * <p>Returns the current variable resolver.</p>
     *
     * @return Current variable resolver
     */
    public XPathVariableResolver getXPathVariableResolver() {
        return variableResolver;
    }

    
Establishes a function resolver.


Params:
  • resolver – XPath function resolver
/**
     * <p>Establishes a function resolver.</p>
     *
     * @param resolver XPath function resolver
     */
    public void setXPathFunctionResolver(XPathFunctionResolver resolver) {
        if ( resolver == null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"XPathFunctionResolver"} );
            throw new NullPointerException( fmsg );
        }
        this.functionResolver = resolver;
    }

    
Returns the current function resolver.


Returns:Current function resolver
/**
     * <p>Returns the current function resolver.</p>
     *
     * @return Current function resolver
     */
    public XPathFunctionResolver getXPathFunctionResolver() {
        return functionResolver;
    }

    
Establishes a namespace context.


Params:
  • nsContext – Namespace context to use
/**
     * <p>Establishes a namespace context.</p>
     *
     * @param nsContext Namespace context to use
     */
    public void setNamespaceContext(NamespaceContext nsContext) {
        if ( nsContext == null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"NamespaceContext"} );
            throw new NullPointerException( fmsg ); 
        }
        this.namespaceContext = nsContext;
        this.prefixResolver = new JAXPPrefixResolver ( nsContext );
    }

    
Returns the current namespace context.


Returns:Current Namespace context
/**
     * <p>Returns the current namespace context.</p>
     *
     * @return Current Namespace context
     */
    public NamespaceContext getNamespaceContext() {
        return namespaceContext;
    }

    private static Document d = null;
    
    private static DocumentBuilder getParser() {
        try {
            // we'd really like to cache those DocumentBuilders, but we can't because:
            // 1. thread safety. parsers are not thread-safe, so at least
            //    we need one instance per a thread.
            // 2. parsers are non-reentrant, so now we are looking at having a
            // pool of parsers.
            // 3. then the class loading issue. The look-up procedure of
            //    DocumentBuilderFactory.newInstance() depends on context class loader
            //    and system properties, which may change during the execution of JVM.
            //
            // so we really have to create a fresh DocumentBuilder every time we need one
            // - KK
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            dbf.setNamespaceAware( true );
            dbf.setValidating( false );
            return dbf.newDocumentBuilder();
        } catch (ParserConfigurationException e) {
            // this should never happen with a well-behaving JAXP implementation. 
            throw new Error(e.toString());
        }
    }

    private static Document getDummyDocument( ) {
        // we don't need synchronization here; even if two threads
        // enter this code at the same time, we just waste a little time
        if(d==null) {
            DOMImplementation dim = getParser().getDOMImplementation();
            d = dim.createDocument("http://java.sun.com/jaxp/xpath",
                "dummyroot", null);
        }
        return d;
    }

    
    private XObject eval(String expression, Object contextItem)
        throws javax.xml.transform.TransformerException {
        org.apache.xpath.XPath xpath = new org.apache.xpath.XPath( expression,
            null, prefixResolver, org.apache.xpath.XPath.SELECT ); 
        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);
        }

        XObject xobj = null;
        
        xpathSupport.setVarStack(new JAXPVariableStack(variableResolver));
        
        // If item is null, then we will create a a Dummy contextNode
        if ( contextItem instanceof Node ) {
            xobj = xpath.execute (xpathSupport, (Node)contextItem,
                    prefixResolver );
        } else {
            xobj = xpath.execute ( xpathSupport, DTM.NULL, prefixResolver );
        }
 
        return xobj;
    }
        
    
Evaluate an 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 XPathConstants ( NUMBER, STRING, BOOLEAN, NODE or NODESET) then an IllegalArgumentException is thrown.


If a null value is provided for
item, an empty document will be used for the
context.
If expression or returnType is null, then a
NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • item – The starting context (node or node list, for example).
  • returnType – The desired return type.
Throws:
Returns:Result of evaluating an XPath expression as an Object of returnType.
/**
     * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as the specified type.</p>
     *
     * <p>See "Evaluation of XPath Expressions" section of JAXP 1.3 spec
     * for context item evaluation,
     * variable, function and <code>QName</code> resolution and return type conversion.</p>
     *
     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (
     * {@link XPathConstants#NUMBER NUMBER},
     * {@link XPathConstants#STRING STRING},
     * {@link XPathConstants#BOOLEAN BOOLEAN},
     * {@link XPathConstants#NODE NODE} or
     * {@link XPathConstants#NODESET NODESET})
     * then an <code>IllegalArgumentException</code> is thrown.</p>
     *
     * <p>If a <code>null</code> value is provided for
     * <code>item</code>, an empty document will be used for the
     * context.
     * If <code>expression</code> or <code>returnType</code> is <code>null</code>, then a
     * <code>NullPointerException</code> is thrown.</p>
     *
     * @param expression The XPath expression.
     * @param item The starting context (node or node list, for example).
     * @param returnType The desired return type.
     *
     * @return Result of evaluating an XPath expression as an <code>Object</code> of <code>returnType</code>.
     *
     * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
     * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is <code>null</code>.
     */
    public Object evaluate(String expression, Object item, QName returnType)
            throws XPathExpressionException {
        if ( expression == null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"XPath expression"} );
            throw new NullPointerException ( fmsg );
        }
        if ( returnType == null ) {
            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 {
 
            XObject resultObject = eval( expression, item );
            return getResultAsType( resultObject, 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 );
            }
        } 
        
    }

    private boolean isSupported( QName returnType ) {
        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();
        }
        String fmsg = XSLMessages.createXPATHMessage(
                XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
                new Object[] { returnType.toString()});
        throw new IllegalArgumentException( fmsg );
    }
         
            
        
    
Evaluate an XPath expression in the specified context and return the result as a String.


This method calls evaluate(String expression, Object item, QName returnType) with a returnType of XPathConstants.STRING.


See "Evaluation of XPath Expressions" 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.
If expression is null, then a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • item – The starting context (node or node list, for example).
Throws:
Returns:The String that is the result of evaluating the expression and
  converting the result to a String.
/**
     * <p>Evaluate an XPath expression in the specified context and return the result as a <code>String</code>.</p>
     *
     * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a <code>returnType</code> of
     * {@link XPathConstants#STRING}.</p>
     *
     * <p>See "Evaluation of XPath Expressions" of JAXP 1.3 spec 
     * for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     *
     * <p>If a <code>null</code> value is provided for
     * <code>item</code>, an empty document will be used for the
     * context.
     * If <code>expression</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
     *
     * @param expression The XPath expression.
     * @param item The starting context (node or node list, for example).
     *
     * @return The <code>String</code> that is the result of evaluating the expression and
     *   converting the result to a <code>String</code>.
     *
     * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
     * @throws NullPointerException If <code>expression</code> is <code>null</code>.
     */
    public String evaluate(String expression, Object item)
        throws XPathExpressionException {
        return (String)this.evaluate( expression, item, XPathConstants.STRING );
    }

    
Compile an XPath expression for later evaluation.


If expression contains any XPathFunctions, they must be available via the XPathFunctionResolver. An XPathExpressionException will be thrown if the XPathFunction
cannot be resovled with the XPathFunctionResolver.


If expression is null, a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
Throws:
Returns:Compiled XPath expression.
/**
     * <p>Compile an XPath expression for later evaluation.</p>
     *
     * <p>If <code>expression</code> contains any {@link XPathFunction}s,
     * they must be available via the {@link XPathFunctionResolver}.
     * An {@link XPathExpressionException} will be thrown if the <code>XPathFunction</code>
     * cannot be resovled with the <code>XPathFunctionResolver</code>.</p>
     * 
     * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is thrown.</p>
     *
     * @param expression The XPath expression.
     *
     * @return Compiled XPath expression.

     * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
     * @throws NullPointerException If <code>expression</code> is <code>null</code>.
     */
    public XPathExpression compile(String expression)
        throws XPathExpressionException {
        if ( expression == null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"XPath expression"} );
            throw new NullPointerException ( fmsg );
        }
        try {
            org.apache.xpath.XPath xpath = new XPath (expression, null,
                    prefixResolver, org.apache.xpath.XPath.SELECT );
            // Can have errorListener
            XPathExpressionImpl ximpl = new XPathExpressionImpl (xpath,
                    prefixResolver, functionResolver, variableResolver,
                    featureSecureProcessing );
            return ximpl;
        } catch ( javax.xml.transform.TransformerException te ) {
            throw new XPathExpressionException ( te ) ;
        }
    }


    
Evaluate an 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 InputSource and calls evaluate(String expression, 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 XPathConstants, then an IllegalArgumentException is thrown.


If expression, source or returnType is null,
then a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • source – The input source of the document to evaluate over.
  • returnType – The desired return type.
Throws:
Returns:The Object that encapsulates the result of evaluating the expression.
/**
     * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
     * and return the result as the specified type.</p>
     *
     * <p>This method builds a data model for the {@link InputSource} and calls
     * {@link #evaluate(String expression, Object item, QName returnType)} on the resulting document object.</p>
     *
     * <p>See "Evaluation of XPath Expressions" section of JAXP 1.3 spec 
     * for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     *
     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
     * then an <code>IllegalArgumentException</code> is thrown.</p>
     *
     * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is <code>null</code>,
     * then a <code>NullPointerException</code> is thrown.</p>
     *
     * @param expression The XPath expression.
     * @param source The input source of the document to evaluate over.
     * @param returnType The desired return type.
     *
     * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
     *
     * @throws XPathExpressionException If expression cannot be evaluated.
     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
     * @throws NullPointerException If <code>expression</code>, <code>source</code> or <code>returnType</code>
     *   is <code>null</code>.
     */
    public Object evaluate(String expression, InputSource source, 
            QName returnType) throws XPathExpressionException {
        // Checking validity of different parameters
        if( source== null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"source"} );
            throw new NullPointerException ( fmsg );
        }
        if ( expression == null ) {
            String fmsg = XSLMessages.createXPATHMessage( 
                    XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                    new Object[] {"XPath expression"} );
            throw new NullPointerException ( fmsg );
        }
        if ( returnType == null ) {
            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 {

            Document document = getParser().parse( source );

            XObject resultObject = eval( expression, document );
            return getResultAsType( resultObject, returnType );
        } catch ( SAXException e ) {
            throw new XPathExpressionException ( e );
        } catch( IOException e ) {
            throw new XPathExpressionException ( e );            
        } catch ( javax.xml.transform.TransformerException te ) {
            Throwable nestedException = te.getException();
            if ( nestedException instanceof javax.xml.xpath.XPathFunctionException ) {
                throw (javax.xml.xpath.XPathFunctionException)nestedException;
            } else {
                throw new XPathExpressionException ( te );
            }
        }

    } 
 



    
Evaluate an XPath expression in the context of the specified InputSource
and return the result as a String.


This method calls evaluate(String expression, InputSource source, QName returnType) with a returnType of 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 expression or source is null,
then a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • source – The InputSource of the document to evaluate over.
Throws:
Returns:The String that is the result of evaluating the expression and
  converting the result to a String.
/**
     * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
     * and return the result as a <code>String</code>.</p>
     *
     * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)} with a
     * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
     *
     * <p>See "Evaluation of XPath Expressions" section of JAXP 1.3 spec
     * for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     *
     * <p>If <code>expression</code> or <code>source</code> is <code>null</code>,
     * then a <code>NullPointerException</code> is thrown.</p>
     *
     * @param expression The XPath expression.
     * @param source The <code>InputSource</code> of the document to evaluate over.
     *
     * @return The <code>String</code> that is the result of evaluating the expression and
     *   converting the result to a <code>String</code>.
     *
     * @throws XPathExpressionException If expression cannot be evaluated.
     * @throws NullPointerException If <code>expression</code> or <code>source</code> is <code>null</code>.
     */
    public String evaluate(String expression, InputSource source)
        throws XPathExpressionException {
        return (String)this.evaluate( expression, source, XPathConstants.STRING );
    }

    
Reset this XPath to its original configuration.


XPath is reset to the same state as when it was created with XPathFactory.newXPath(). reset() is designed to allow the reuse of existing XPaths
thus saving resources associated with the creation of new XPaths.


The reset XPath is not guaranteed to have the same XPathFunctionResolver, XPathVariableResolver or NamespaceContext Objects, e.g. Object.equals(Object obj). It is guaranteed to have a functionally equal XPathFunctionResolver,
XPathVariableResolver
and NamespaceContext.


/**
     * <p>Reset this <code>XPath</code> to its original configuration.</p>
     *
     * <p><code>XPath</code> is reset to the same state as when it was created with
     * {@link XPathFactory#newXPath()}.
     * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s
     * thus saving resources associated with the creation of new <code>XPath</code>s.</p>
     *
     * <p>The reset <code>XPath</code> is not guaranteed to have the same
     * {@link XPathFunctionResolver}, {@link XPathVariableResolver}
     * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.
     * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>,
     * <code>XPathVariableResolver</code>
     * and <code>NamespaceContext</code>.</p>
     */
    public void reset() {
        this.variableResolver = this.origVariableResolver;
        this.functionResolver = this.origFunctionResolver;
        this.namespaceContext = null;
    }
 
}