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## net.sf.saxon.instruct
Class ComputedAttribute

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.instruct.Instruction
              net.sf.saxon.instruct.SimpleNodeConstructor
                  net.sf.saxon.instruct.ComputedAttribute

All Implemented Interfaces:
  Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, TailCallReturner, InstructionInfoProvider

    public final class ComputedAttribute

extends SimpleNodeConstructor

An instruction derived from an xsl:attribute element in stylesheet, or from an attribute constructor in XQuery, in cases where the attribute name is not known statically

See Also:
  Serialized Form

Field Summary

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

Constructor Summary
`ComputedAttribute(Expression attributeName, Expression namespace, NamespaceResolver nsContext, int validationAction, SimpleType schemaType, int annotation, boolean allowNameAsQName)` Construct an Attribute instruction

Method Summary
`void` | `checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole)` Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
`int` | `computeSpecialProperties()` Get the static properties of this expression (other than its type).
`void` | `display(int level, PrintStream out, Configuration config)` Display this instruction as an expression, for diagnostics
`int` | `evaluateNameCode(XPathContext context)` Determine the name to be used for the attribute, as an integer name code
`int` | `getCardinality()` Determine the static cardinality of the expression.
`int` | `getInstructionNameCode()` Get the name of this instruction
`ItemType` | `getItemType(TypeHierarchy th)` Get the item type of the items returned by evaluating this instruction
`Expression` | `getNameExpression()`
`Expression` | `getNamespaceExpression()`
`NamespaceResolver` | `getNamespaceResolver()`
`Iterator` | `iterateSubExpressions()` Get the subexpressions of this expression
`void` | `localTypeCheck(StaticContext env, ItemType contextItemType)` Method to perform type-checking specific to the kind of instruction
`TailCall` | `processLeavingTail(XPathContext context)` Process this instruction
`boolean` | `replaceSubExpression(Expression original, Expression replacement)` Replace one subexpression by a replacement subexpression
`void` | `setRejectDuplicates()` Indicate that two attributes with the same name are not acceptable.
`Expression` | `simplify(StaticContext env)` Simplify an expression.

Methods inherited from class net.sf.saxon.instruct.SimpleNodeConstructor
`computeCardinality, createsNewNodes, evaluateItem, expandChildren, getSelect, iterate, optimize, setSelect, typeCheck`

Methods inherited from class net.sf.saxon.instruct.Instruction
`appendItem, evaluateAsString, getImplementationMethod, getInstructionInfo, getSourceLocator, isXSLT, process, promote`

Methods inherited from class net.sf.saxon.expr.Expression
`adoptChildExpression, computeDependencies, computeStaticProperties, doPromotion, effectiveBooleanValue, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation`

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

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

Constructor Detail

### ComputedAttribute

    public ComputedAttribute(Expression attributeName,
                             Expression namespace,
                             NamespaceResolver nsContext,
                             int validationAction,
                             SimpleType schemaType,
                             int annotation,
                             boolean allowNameAsQName)

  Construct an Attribute instruction

  Parameters:
    `attributeName` - An expression to calculate the attribute name
    `namespace` - An expression to calculate the attribute namespace
    `nsContext` - a NamespaceContext object containing the static namespace context of the stylesheet instruction
    `validationAction` - e.g. validation=strict, lax, strip, preserve
    `schemaType` - Type against which the attribute must be validated. This must not be a namespace-sensitive type; it is the caller's responsibility to check this.
    `annotation` - Integer code identifying the type named in the `type` attribute
    `allowNameAsQName` -

Method Detail

### setRejectDuplicates

    public void setRejectDuplicates()

  Indicate that two attributes with the same name are not acceptable. (This option is set in XQuery, but not in XSLT)

### getInstructionNameCode

    public int getInstructionNameCode()

  Get the name of this instruction

  Overrides:
    `getInstructionNameCode` in class `Instruction`

### getNameExpression

    public Expression getNameExpression()

### getNamespaceExpression

    public Expression getNamespaceExpression()

### getNamespaceResolver

    public NamespaceResolver getNamespaceResolver()

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Description copied from class: `Instruction`
  Get the item type of the items returned by evaluating this instruction

  Overrides:
    `getItemType` in class `Instruction`
  Returns:
    the static item type of the instruction

### getCardinality

    public int getCardinality()

  Description copied from class: `Expression`
  Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.

  Overrides:
    `getCardinality` in class `Expression`
  Returns:
    one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

### 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 `SimpleNodeConstructor`
  Returns:
    a set of flags indicating static properties of this expression

### 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.

  Overrides:
    `simplify` in class `SimpleNodeConstructor`
  Returns:
    the simplified expression
  Throws:
    `XPathException` - if an error is discovered during expression rewriting

### localTypeCheck

    public void localTypeCheck(StaticContext env,
                               ItemType contextItemType)
                        throws XPathException

  Description copied from class: `SimpleNodeConstructor`
  Method to perform type-checking specific to the kind of instruction

  Specified by:
    `localTypeCheck` in class `SimpleNodeConstructor`
  Throws:
    `XPathException`

### iterateSubExpressions

    public Iterator iterateSubExpressions()

  Get the subexpressions of this expression

  Overrides:
    `iterateSubExpressions` in class `SimpleNodeConstructor`
  Returns:
    an iterator over the subexpressions

### replaceSubExpression

    public boolean replaceSubExpression(Expression original,
                                        Expression replacement)

  Replace one subexpression by a replacement subexpression

  Specified by:
    `replaceSubExpression` in interface `Container`
  Overrides:
    `replaceSubExpression` in class `SimpleNodeConstructor`
  Parameters:
    `original` - the original subexpression
    `replacement` - the replacement subexpression
  Returns:
    true if the original subexpression is found

### checkPermittedContents

    public void checkPermittedContents(SchemaType parentType,
                                       StaticContext env,
                                       boolean whole)
                                throws XPathException

  Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.

  Overrides:
    `checkPermittedContents` in class `Expression`
  Throws:
    `XPathException`

### processLeavingTail

    public TailCall processLeavingTail(XPathContext context)
                                throws XPathException

  Process this instruction

  Specified by:
    `processLeavingTail` in interface `TailCallReturner`
  Specified by:
    `processLeavingTail` in class `Instruction`
  Parameters:
    `context` - the dynamic context of the transformation
  Returns:
    a TailCall to be executed by the caller, always null for this instruction
  Throws:
    `XPathException`

### evaluateNameCode

    public int evaluateNameCode(XPathContext context)
                         throws XPathException

  Determine the name to be used for the attribute, as an integer name code

  Overrides:
    `evaluateNameCode` in class `SimpleNodeConstructor`
  Parameters:
    `context` - Dynamic evaluation context
  Returns:
    the integer name code for the attribute name
  Throws:
    `XPathException`

### display

    public void display(int level,
                        PrintStream out,
                        Configuration config)

  Display this instruction as an expression, for diagnostics

  Overrides:
    `display` in class `SimpleNodeConstructor`
  Parameters:
    `level` - indentation level for this expression
    `out` - Output destination

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Copyright (C) Michael H. Kay. All rights reserved.