## net.sf.saxon.style
Class UseWhenFilter

    java.lang.Object
      net.sf.saxon.event.SequenceReceiver
          net.sf.saxon.event.ProxyReceiver
              net.sf.saxon.style.UseWhenFilter

All Implemented Interfaces:
  Result, Receiver

    public class UseWhenFilter

extends ProxyReceiver

This is a filter inserted into the input pipeline for processing stylesheet modules, whose task is to evaluate use-when expressions and discard those parts of the stylesheet module for which the use-when attribute evaluates to false.

Field Summary

Fields inherited from class net.sf.saxon.event.ProxyReceiver
`nextReceiver`

Fields inherited from class net.sf.saxon.event.SequenceReceiver
`pipelineConfiguration, previousAtomic, systemId`

Fields inherited from interface javax.xml.transform.Result
`PI_DISABLE_OUTPUT_ESCAPING, PI_ENABLE_OUTPUT_ESCAPING`

Constructor Summary
`UseWhenFilter(StartTagBuffer startTag)` Create a UseWhenFilter

Method Summary
`void` `attribute(int nameCode, int typeCode, CharSequence value, int locationId, int properties)` Notify an attribute.
`void` `characters(CharSequence chars, int locationId, int properties)` Character data
`void` `comment(CharSequence chars, int locationId, int properties)` Output a comment
`void` `endElement()` End of element
`boolean` `evaluateUseWhen(String expression, int locationId)` Evaluate a use-when attribute
`void` `namespace(int namespaceCode, int properties)` Notify a namespace.
`void` `open()` Start of document
`void` `processingInstruction(String target, CharSequence data, int locationId, int properties)` Processing Instruction
`void` `startContent()` Notify the start of the content, that is, the completion of all attributes and namespaces.
`void` `startElement(int nameCode, int typeCode, int locationId, int properties)` Notify the start of an element.

Methods inherited from class net.sf.saxon.event.ProxyReceiver
`append, close, endDocument, getConfiguration, getDocumentLocator, getNamePool, getUnderlyingReceiver, setPipelineConfiguration, setSystemId, setUnderlyingReceiver, setUnparsedEntity, startDocument, usesTypeAnnotations`

Methods inherited from class net.sf.saxon.event.SequenceReceiver
`append, getPipelineConfiguration, getSystemId`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### UseWhenFilter

    public UseWhenFilter(StartTagBuffer startTag)

  Create a UseWhenFilter

  Parameters:
    `startTag` - a preceding filter on the pipeline that buffers the attributes of a start tag

Method Detail

### open

    public void open()
              throws XPathException

  Start of document

  Specified by:
    `open` in interface `Receiver`
  Overrides:
    `open` in class `ProxyReceiver`
  Throws:
    `XPathException`

### startElement

    public void startElement(int nameCode,
                             int typeCode,
                             int locationId,
                             int properties)
                      throws XPathException

  Notify the start of an element.

  Specified by:
    `startElement` in interface `Receiver`
  Overrides:
    `startElement` in class `ProxyReceiver`
  Parameters:
    `nameCode` - integer code identifying the name of the element within the name pool.
    `typeCode` - integer code identifying the element's type within the name pool.
    `properties` - bit-significant properties of the element node
    `locationId` - an integer which can be interpreted using a `LocationProvider` to return information such as line number and system ID. If no location information is available, the value zero is supplied.
  Throws:
    `XPathException`

### namespace

    public void namespace(int namespaceCode,
                          int properties)
                   throws XPathException

  Notify a namespace. Namespaces are notified after the startElement event, and before any children for the element. The namespaces that are reported are only required to include those that are different from the parent element; however, duplicates may be reported. A namespace must not conflict with any namespaces already used for element or attribute names.

  Specified by:
    `namespace` in interface `Receiver`
  Overrides:
    `namespace` in class `ProxyReceiver`
  Parameters:
    `namespaceCode` - an integer: the top half is a prefix code, the bottom half a URI code. These may be translated into an actual prefix and URI using the name pool. A prefix code of zero represents the empty prefix (that is, the default namespace). A URI code of zero represents a URI of "", that is, a namespace undeclaration.
    `properties` - The most important property is REJECT_DUPLICATES. If this property is set, the namespace declaration will be rejected if it conflicts with a previous declaration of the same prefix. If the property is not set, the namespace declaration will be ignored if it conflicts with a previous declaration. This reflects the fact that when copying a tree, namespaces for child elements are emitted before the namespaces of their parent element. Unfortunately this conflicts with the XSLT rule for complex content construction, where the recovery action in the event of conflicts is to take the namespace that comes last. XSLT therefore doesn't recover from this error: it sets the REJECT_DUPLICATES flag, and this is treated as a hard error.
  Throws:
    `IllegalStateException:` - attempt to output a namespace when there is no open element start tag
    `XPathException`

### attribute

    public void attribute(int nameCode,
                          int typeCode,
                          CharSequence value,
                          int locationId,
                          int properties)
                   throws XPathException

  Notify an attribute. Attributes are notified after the startElement event, and before any children. Namespaces and attributes may be intermingled.

  Specified by:
    `attribute` in interface `Receiver`
  Overrides:
    `attribute` in class `ProxyReceiver`
  Parameters:
    `nameCode` - The name of the attribute, as held in the name pool
    `typeCode` - The type of the attribute, as held in the name pool
    `properties` - Bit significant value. The following bits are defined:
    DISABLE_ESCAPING
  Disable escaping for this attribute
    NO_SPECIAL_CHARACTERS
  Attribute value contains no special characters
    `value` - the string value of the attribute
    `locationId` - an integer which can be interpreted using a `LocationProvider` to return information such as line number and system ID. If no location information is available, the value zero is supplied.
  Throws:
    `IllegalStateException:` - attempt to output an attribute when there is no open element start tag
    `XPathException`

### startContent

    public void startContent()
                      throws XPathException

  Notify the start of the content, that is, the completion of all attributes and namespaces. Note that the initial receiver of output from XSLT instructions will not receive this event, it has to detect it itself. Note that this event is reported for every element even if it has no attributes, no namespaces, and no content.

  Specified by:
    `startContent` in interface `Receiver`
  Overrides:
    `startContent` in class `ProxyReceiver`
  Throws:
    `XPathException`

### endElement

    public void endElement()
                    throws XPathException

  End of element

  Specified by:
    `endElement` in interface `Receiver`
  Overrides:
    `endElement` in class `ProxyReceiver`
  Throws:
    `XPathException`

### characters

    public void characters(CharSequence chars,
                           int locationId,
                           int properties)
                    throws XPathException

  Character data

  Specified by:
    `characters` in interface `Receiver`
  Overrides:
    `characters` in class `ProxyReceiver`
  Parameters:
    `chars` - The characters
    `locationId` - an integer which can be interpreted using a `LocationProvider` to return information such as line number and system ID. If no location information is available, the value zero is supplied.
    `properties` - Bit significant value. The following bits are defined:
  DISABLE_ESCAPING
    Disable escaping for this text node
  USE_CDATA
    Output as a CDATA section
  Throws:
    `XPathException`

### processingInstruction

    public void processingInstruction(String target,
                                      CharSequence data,
                                      int locationId,
                                      int properties)

  Processing Instruction

  Specified by:
    `processingInstruction` in interface `Receiver`
  Overrides:
    `processingInstruction` in class `ProxyReceiver`
  Parameters:
    `target` - The PI name. This must be a legal name (it will not be checked).
    `data` - The data portion of the processing instruction
    `locationId` - an integer which can be interpreted using a `LocationProvider` to return information such as line number and system ID. If no location information is available, the value zero is supplied.
    `properties` - Additional information about the PI.

### comment

    public void comment(CharSequence chars,
                        int locationId,
                        int properties)
                 throws XPathException

  Output a comment

  Specified by:
    `comment` in interface `Receiver`
  Overrides:
    `comment` in class `ProxyReceiver`
  Parameters:
    `chars` - The content of the comment
    `locationId` - an integer which can be interpreted using a `LocationProvider` to return information such as line number and system ID. If no location information is available, the value zero is supplied.
    `properties` - Additional information about the comment.
  Throws:
    `XPathException`

### evaluateUseWhen

    public boolean evaluateUseWhen(String expression,
                                   int locationId)
                            throws XPathException

  Evaluate a use-when attribute

  Parameters:
    `expression` - the expression to be evaluated
    `locationId` - identifies the location of the expression in case error need to be reported
  Returns:
    the effective boolean value of the result of evaluating the expression
  Throws:
    `XPathException`

Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.