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XPathExpressionImpl.javaAPI DocJava SE 5 API15920Fri Aug 26 14:56:10 BST 2005com.sun.org.apache.xpath.internal.jaxp

XPathExpressionImpl

public class XPathExpressionImpl extends Object implements XPathExpression
The XPathExpression interface encapsulates a (compiled) XPath expression.
version
$Revision: 1.8 $
author
Ramesh Mandava

Fields Summary
private XPathFunctionResolver
functionResolver
private XPathVariableResolver
variableResolver
private JAXPPrefixResolver
prefixResolver
private XPath
xpath
private boolean
featureSecureProcessing
static DocumentBuilderFactory
dbf
static DocumentBuilder
db
static Document
d
Constructors Summary
protected XPathExpressionImpl()
Protected constructor to prevent direct instantiation; use compile() from the context.
protected XPathExpressionImpl(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(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;
Methods Summary
public java.lang.Objecteval(java.lang.Object item, javax.xml.namespace.QName returnType)

        XObject resultObject = eval ( item );
        return getResultAsType( resultObject, returnType );
private com.sun.org.apache.xpath.internal.objects.XObjecteval(java.lang.Object contextItem)

        com.sun.org.apache.xpath.internal.XPathContext xpathSupport = null;
        if ( functionResolver != null ) {
            JAXPExtensionsProvider jep = new JAXPExtensionsProvider(
                    functionResolver, featureSecureProcessing );
            xpathSupport = new com.sun.org.apache.xpath.internal.XPathContext( jep );
        } else {
            xpathSupport = new com.sun.org.apache.xpath.internal.XPathContext();
        }

        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;
public java.lang.Stringevaluate(org.xml.sax.InputSource source)

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.

        return (String)this.evaluate( source, XPathConstants.STRING );
public java.lang.Objectevaluate(java.lang.Object item, javax.xml.namespace.QName returnType)

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.

        //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);
            }
        }
public java.lang.Stringevaluate(java.lang.Object item)

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.

        return (String)this.evaluate( item, XPathConstants.STRING );
public java.lang.Objectevaluate(org.xml.sax.InputSource source, javax.xml.namespace.QName returnType)

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.


                                                                                                                                                                             
         
          
        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 );
        }
private static org.w3c.dom.DocumentgetDummyDocument()

        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;
private java.lang.ObjectgetResultAsType(com.sun.org.apache.xpath.internal.objects.XObject resultObject, javax.xml.namespace.QName returnType)

        // 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 new Boolean( resultObject.bool());
        }
        // 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 booleanisSupported(javax.xml.namespace.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;
public voidsetXPath(com.sun.org.apache.xpath.internal.XPath xpath)

        this.xpath = xpath;