iaik.ixsil.algorithms

Class TransformImplXPath

java.lang.Object

iaik.ixsil.algorithms.Algorithm

iaik.ixsil.algorithms.Transform

iaik.ixsil.algorithms.TransformImplXPath

public class TransformImplXPath
extends Transform

Provides an transform implementation of the XPath Filtering algorithm, as it has been specified in XML Signature, XPath Filtering .

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	TransformImplXPath.NSDeclaration Auxilary class representing a XML namespace declaration structure.

Field Summary

Fields

Modifier and Type	Field and Description
protected static java.lang.String	DEFAULT_ALGORITHM_URI_ The default algorithm URI for this algorithm implementation.
protected java.lang.String	xPath_ The XPath expression to be processed by this algorithm.
protected java.util.ArrayList	xPathNSDeclarations_ The namespace declarations to be added to the XPath parameter element.
protected org.w3c.dom.Element	xPathParamDOMElem_ The XPath parameter element which will act as the namespace context node for the XPath transform.

Fields inherited from class iaik.ixsil.algorithms.Transform

inputNodeSet_, inputOctetStream_, inputURI_

Fields inherited from class iaik.ixsil.algorithms.Algorithm

uri_

Constructor Summary

Constructors

Constructor and Description
TransformImplXPath() Standard constructor.

Method Summary

Modifier and Type	Method and Description
void	addNSDeclaration(java.lang.String nSPrefix, URI nSURI) Adds a namespace declaration to the list of namespace declarations, which will be used as the namespace context at evaluation of the XPath expression of this transform.
protected void	checkBackingDOM() In case that the XPath expression contains the here() function, checks if the input node set is backed by the same DOM instance as the DOM representation of the XPath parameter element.
java.lang.String	getXPath() Gets the XPath expression to be processed by this transform.
org.w3c.dom.Element	getXPathElement() Gets the XPath DOM element of this transform.
void	setParameters(org.w3c.dom.Element transformElement) Sets the parameters for this XPath transform implementation.
void	setXPath(java.lang.String xPath) Sets the XPath expression to be processed by this transform.
org.w3c.dom.Element	toElement(org.w3c.dom.Document signatureDOMDoc) Returns the DOM element representation of the transform.
java.lang.Object	transform() Computes the transform result for the previously specified input.

Methods inherited from class iaik.ixsil.algorithms.Transform

distributeNSDeclarations, setInput, setInput, skipStylesheetElem, withdrawDistributedNSDeclarations

Methods inherited from class iaik.ixsil.algorithms.Algorithm

getURI, setURI

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_ALGORITHM_URI_

protected static final java.lang.String DEFAULT_ALGORITHM_URI_

The default algorithm URI for this algorithm implementation.

See Also:

Constant Field Values

xPath_

protected java.lang.String xPath_

The XPath expression to be processed by this algorithm.

xPathParamDOMElem_

protected org.w3c.dom.Element xPathParamDOMElem_

The XPath parameter element which will act as the namespace context node for the XPath transform.

xPathNSDeclarations_

protected java.util.ArrayList xPathNSDeclarations_

The namespace declarations to be added to the XPath parameter element.

Constructor Detail

TransformImplXPath

public TransformImplXPath()

Standard constructor. Sets the default value for the algorithm URI to http://www.w3.org/TR/1999/REC-xpath-19991116.

Method Detail

setParameters

public void setParameters(org.w3c.dom.Element transformElement)
                   throws AlgorithmException

Sets the parameters for this XPath transform implementation. A XPath transform has one explicit para- meter element named "XPath", which contains the XPath expression to be processed, as a text value. The namespace attributes in scope for this XPath parameter element will be usedas the namespace context at evaluation of the XPath expression.

Overrides:

setParameters in class Algorithm

Parameters:

transformElement - The DOM element representation of the transform, as it will be found by IXSIL in the XML signature.

Throws:

AlgorithmException - if the XPath parameter element cannot be found, or if the Xpath meter element does not contain any text value, or if setting the parameter fails for any other reason.

getXPathElement

public org.w3c.dom.Element getXPathElement()

Gets the XPath DOM element of this transform.

Returns:

The XPath DOM element of this transform.

setXPath

public void setXPath(java.lang.String xPath)

Sets the XPath expression to be processed by this transform.

Parameters:

xPath - The XPath expression to be processed by this transform.

getXPath

public java.lang.String getXPath()

Gets the XPath expression to be processed by this transform.

Returns:

The XPath expression to be processed by this transform.

addNSDeclaration

public void addNSDeclaration(java.lang.String nSPrefix,
                             URI nSURI)

Adds a namespace declaration to the list of namespace declarations, which will be used as the namespace context at evaluation of the XPath expression of this transform. If namespace prefixes are used in the XPath expression, which are not in scope for the XPath transform parameter element ("XPath"), these prefixes must be declared with this method.

Parameters:

nSPrefix - The namespace prefix to be declared. Must not be null and must not be the empty string.

nSURI - The namespace URI for the namespace prefix to be declared. Must not be null and must not be the empty string.

toElement

public org.w3c.dom.Element toElement(org.w3c.dom.Document signatureDOMDoc)
                              throws AlgorithmException

Returns the DOM element representation of the transform. Used by IXSIL to incorporate the transform into the XML representation of the signature.

Specified by:

toElement in class Algorithm

Parameters:

signatureDOMDoc - The DOM document which should be used to create necessary DOM nodes.

Returns:

the DOM element representation of the transform.

Throws:

AlgorithmException - if no identifying URI has been specified for this transform, or if no XPath expression has been specified for this transform.

transform

public java.lang.Object transform()
                           throws AlgorithmException

Computes the transform result for the previously specified input. If the input has been specified as a octet stream, the octet stream is interpreted as physical representation of a well-formed XML document, parsed and converted to a XPath node set which contains all nodes of the document. The XPath node set is transformed into the result according to the XPath Filtering specification (see description of this class), evaluating the XPath expression previously set as paramater of this transform.

Specified by:

transform in class Transform

Returns:

the result of the transformation process as XPath node set.

Throws:

AlgorithmException - if no input has been set previously, or if no XPath expression has been set previously, or if converting a input octet stream into a XPath node set input fails, or if performing the transform fails for any reason.

checkBackingDOM

protected void checkBackingDOM()
                        throws AlgorithmException

In case that the XPath expression contains the here() function, checks if the input node set is backed by the same DOM instance as the DOM representation of the XPath parameter element. If not, throws an exception to inform the user that this is a malformed transform configuration.

Throws:

AlgorithmException - if the condition specified above is not met.