## net.sf.saxon.instruct
Class SimpleNodeConstructor

    java.lang.Object
      net.sf.saxon.expr.ComputedExpression
          net.sf.saxon.instruct.Instruction
              net.sf.saxon.instruct.SimpleNodeConstructor

All Implemented Interfaces:
  Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

Direct Known Subclasses:
  Attribute, Comment, FixedAttribute, Namespace, ProcessingInstruction, ValueOf

public abstract class SimpleNodeConstructor
extends Instruction

Common superclass for XSLT instructions whose content template produces a text value: xsl:attribute, xsl:comment, xsl:processing-instruction, xsl:namespace, and xsl:text

See Also:
  Serialized Form

Field Summary
`protected Expression` `select`

Fields inherited from class net.sf.saxon.expr.ComputedExpression
`locationId, staticProperties`

Fields inherited from interface net.sf.saxon.expr.Expression
`EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD`

Constructor Summary
`SimpleNodeConstructor()`

Method Summary
`Expression` `analyze(StaticContext env, ItemType contextItemType)` The analyze() method is called in XQuery, where node constructors are implemented as Expressions.
`protected java.lang.String` `checkContent(java.lang.String data, XPathContext context)` Check the content of the node, and adjust it if necessary.
`int` `computeSpecialProperties()` Get the static properties of this expression (other than its type).
`boolean` `createsNewNodes()` Determine whether this instruction creates new nodes.
`void` `display(int level, NamePool pool, java.io.PrintStream out)` Display this instruction as an expression, for diagnostics
`Item` `evaluateItem(XPathContext context)` Evaluate as an expression.
`protected int` `evaluateNameCode(XPathContext context)`
`java.lang.CharSequence` `expandChildren(XPathContext context)` Expand the stylesheet elements subordinate to this one, returning the result as a string.
`SequenceIterator` `iterate(XPathContext context)` Return an Iterator to iterate over the values of a sequence.
`java.util.Iterator` `iterateSubExpressions()` Get the immediate sub-expressions of this expression.
`protected void` `promoteInst(PromotionOffer offer)` Offer promotion for subexpressions.
`void` `setSelect(Expression select)`
`Expression` `simplify(StaticContext env)` Simplify an expression.
`abstract void` `typeCheck(StaticContext env, ItemType contextItemType)`

Methods inherited from class net.sf.saxon.instruct.Instruction
`appendItem, assembleParams, assembleTunnelParams, computeCardinality, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, process, processLeavingTail, promote`

Methods inherited from class net.sf.saxon.expr.ComputedExpression

`adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, dynamicError, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, typeError, typeError`

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

Methods inherited from interface javax.xml.transform.SourceLocator
`getColumnNumber, getLineNumber, getPublicId, getSystemId`

Field Detail

### select

    protected Expression select

Constructor Detail

### SimpleNodeConstructor

    public SimpleNodeConstructor()

Method Detail

### setSelect

    public void setSelect(Expression select)
                   throws StaticError

  Throws:
    `StaticError`

### createsNewNodes

    public final boolean createsNewNodes()

  Determine whether this instruction creates new nodes. This implementation returns true.

  Overrides:
    `createsNewNodes` in class `Instruction`

### simplify

    public Expression simplify(StaticContext env)
                        throws XPathException

  Description copied from class: `Instruction`
  Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.

  Specified by:
    `simplify` in interface `Expression`
  Specified by:
    `simplify` in class `Instruction`
  Returns:
    the simplified expression
  Throws:
    `XPathException` - if an error is discovered during expression rewriting

### computeSpecialProperties

    public int computeSpecialProperties()

  Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

  Overrides:
    `computeSpecialProperties` in class `Instruction`
  Returns:
    a set of flags indicating static properties of this expression

### typeCheck

    public abstract void typeCheck(StaticContext env,
                                   ItemType contextItemType)
                            throws XPathException

  Throws:
    `XPathException`

### analyze

    public Expression analyze(StaticContext env,
                              ItemType contextItemType)
                       throws XPathException

  The analyze() method is called in XQuery, where node constructors are implemented as Expressions. In this case the required type for the select expression is a single string.

  Specified by:
    `analyze` in interface `Expression`
  Specified by:
    `analyze` in class `Instruction`
  Parameters:
    `env` - The static context for the query
  Returns:
    the rewritten expression
  Throws:
    `XPathException` - if any static errors are found in this expression or any of its children

### iterateSubExpressions

    public java.util.Iterator iterateSubExpressions()

  Description copied from class: `ComputedExpression`
  Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

  Specified by:
    `iterateSubExpressions` in interface `Expression`
  Overrides:
    `iterateSubExpressions` in class `ComputedExpression`
  Returns:
    an iterator containing the sub-expressions of this expression

### expandChildren

    public java.lang.CharSequence expandChildren(XPathContext context)
                                          throws XPathException

  Expand the stylesheet elements subordinate to this one, returning the result as a string. The expansion must not generate any element or attribute nodes.

  Parameters:
    `context` - The dynamic context for the transformation
  Throws:
    `XPathException`

### evaluateItem

    public Item evaluateItem(XPathContext context)
                      throws XPathException

  Evaluate as an expression. We rely on the fact that when these instructions are generated by XQuery, there will always be a valueExpression to evaluate the content

  Specified by:
    `evaluateItem` in interface `Expression`
  Overrides:
    `evaluateItem` in class `Instruction`
  Parameters:
    `context` - The context in which the expression is to be evaluated
  Returns:
    the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
  Throws:
    `XPathException` - if any dynamic error occurs evaluating the expression

### checkContent

    protected java.lang.String checkContent(java.lang.String data,
                                            XPathContext context)
                                     throws DynamicError

  Check the content of the node, and adjust it if necessary. The checks depend on the node kind.

  Parameters:
    `data` - the supplied content
    `context` - the dynamic context
  Returns:
    the original content, unless adjustments are needed
  Throws:
    `DynamicError` - if the content is invalid

### evaluateNameCode

    protected int evaluateNameCode(XPathContext context)
                            throws XPathException,
                                   XPathException

  Throws:
    `XPathException`

### iterate

    public SequenceIterator iterate(XPathContext context)
                             throws XPathException

  Description copied from class: `Instruction`
  Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

  Specified by:
    `iterate` in interface `Expression`
  Overrides:
    `iterate` in class `Instruction`
  Parameters:
    `context` - supplies the context for evaluation
  Returns:
    a SequenceIterator that can be used to iterate over the result of the expression
  Throws:
    `XPathException` - if any dynamic error occurs evaluating the expression

### display

    public void display(int level,
                        NamePool pool,
                        java.io.PrintStream out)

  Display this instruction as an expression, for diagnostics

  Parameters:
    `level` - indentation level for this expression
    `pool` - NamePool used to expand any names appearing in the expression
    `out` - Output destination

### promoteInst

    protected void promoteInst(PromotionOffer offer)
                        throws XPathException

  Offer promotion for subexpressions. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

  Overrides:
    `promoteInst` in class `Instruction`
  Parameters:
    `offer` - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
  Throws:
    `XPathException` - if any error is detected