net.sf.saxon.instruct
Class ElementCreator

java.lang.Object
  extended bynet.sf.saxon.expr.ComputedExpression
      extended bynet.sf.saxon.instruct.Instruction
          extended bynet.sf.saxon.instruct.ElementCreator
All Implemented Interfaces:
Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator
Direct Known Subclasses:
Copy, Element, FixedElement

public abstract class ElementCreator
extends Instruction

An instruction that creates an element node. There are two subtypes, FixedElement for use where the name is known statically, and Element where it is computed dynamically. To allow use in both XSLT and XQuery, the class acts both as an Instruction and as an Expression.

See Also:
Serialized Form

Field Summary
protected  Expression content
           
protected  boolean inheritNamespaces
          The inheritNamespaces flag indicates that the namespace nodes on the element created by this instruction are to be inherited (copied) on the children of this element.
protected  SchemaType schemaType
           
protected  AttributeSet[] useAttributeSets
           
protected  int validation
           
 
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
ElementCreator()
           
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Perform static analysis of an expression and its subexpressions.
 int computeSpecialProperties()
          Get the static properties of this expression (other than its type).
 boolean createsNewNodes()
          Determine whether this instruction creates new nodes.
 Item evaluateItem(XPathContext context)
          Evaluate as an expression.
 int getCardinality()
          Determine the static cardinality of the expression.
 int getImplementationMethod()
          An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
 ItemType getItemType()
          Get the item type of the value returned by this instruction
protected abstract  int getNameCode(XPathContext context)
           
 int getValidationMode()
          Get the validation mode for the constructed element
 java.util.Iterator iterateSubExpressions()
          Get the immediate sub-expressions of this expression.
protected abstract  void outputNamespaceNodes(XPathContext context, Receiver receiver)
          Callback to output namespace nodes for the new element.
 TailCall processLeavingTail(XPathContext context)
          Evaluate the instruction to produce a new element node
protected  void promoteInst(PromotionOffer offer)
          Handle promotion offers, that is, non-local tree rewrites.
 void setContent(Expression content)
          Set the expression that constructs the content of the element
 void setValidationMode(int mode)
          Set the validation mode for the new element
 Expression simplify(StaticContext env)
          Simplify an expression.
 
Methods inherited from class net.sf.saxon.instruct.Instruction
appendItem, assembleParams, assembleTunnelParams, computeCardinality, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getInstructionInfo, getInstructionNameCode, getSourceLocator, isXSLT, iterate, process, promote
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, dynamicError, 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
 
Methods inherited from interface net.sf.saxon.expr.Expression
display
 

Field Detail

content

protected Expression content

useAttributeSets

protected AttributeSet[] useAttributeSets

schemaType

protected SchemaType schemaType

validation

protected int validation

inheritNamespaces

protected boolean inheritNamespaces
The inheritNamespaces flag indicates that the namespace nodes on the element created by this instruction are to be inherited (copied) on the children of this element. That is, if this flag is false, the child elements must carry a namespace undeclaration for all the namespaces on the parent, unless they are redeclared in some way.

Constructor Detail

ElementCreator

public ElementCreator()
Method Detail

setContent

public void setContent(Expression content)
Set the expression that constructs the content of the element


simplify

public Expression simplify(StaticContext env)
                    throws XPathException
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

analyze

public Expression analyze(StaticContext env,
                          ItemType contextItemType)
                   throws XPathException
Perform static analysis of an expression and its subexpressions.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables will only be accurately known if they have been explicitly declared.

Specified by:
analyze in interface Expression
Specified by:
analyze in class Instruction
Parameters:
env - the static context of the expression
Returns:
the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

promoteInst

protected void promoteInst(PromotionOffer offer)
                    throws XPathException
Handle promotion offers, that is, non-local tree rewrites.

Overrides:
promoteInst in class Instruction
Parameters:
offer - The type of rewrite being offered
Throws:
XPathException

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()
Get the immediate sub-expressions of this expression.

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

createsNewNodes

public final boolean createsNewNodes()
Determine whether this instruction creates new nodes. This implementation returns true.

Overrides:
createsNewNodes in class Instruction

getItemType

public ItemType getItemType()
Get the item type of the value returned by this instruction

Specified by:
getItemType in interface Expression
Overrides:
getItemType in class Instruction
Returns:
the item type

getCardinality

public int getCardinality()
Description copied from class: ComputedExpression
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.

Specified by:
getCardinality in interface Expression
Overrides:
getCardinality in class ComputedExpression
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 Instruction
Returns:
a set of flags indicating static properties of this expression

setValidationMode

public void setValidationMode(int mode)
Set the validation mode for the new element


getValidationMode

public int getValidationMode()
Get the validation mode for the constructed element


getNameCode

protected abstract int getNameCode(XPathContext context)
                            throws XPathException
Throws:
XPathException

outputNamespaceNodes

protected abstract void outputNamespaceNodes(XPathContext context,
                                             Receiver receiver)
                                      throws XPathException
Callback to output namespace nodes for the new element.

Parameters:
context - The execution context
receiver - the Receiver where the namespace nodes are to be written
Throws:
XPathException

getImplementationMethod

public int getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered. For instructions this is the process() method.

Specified by:
getImplementationMethod in interface Expression
Overrides:
getImplementationMethod in class Instruction

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException
Evaluate the instruction to produce a new element node

Specified by:
processLeavingTail in class Instruction
Parameters:
context -
Returns:
null (this instruction never returns a tail call)
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