net.sf.saxon.instruct
Class ParentNodeConstructor

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.instruct.Instruction
          extended by net.sf.saxon.instruct.ParentNodeConstructor
All Implemented Interfaces:
Serializable, SourceLocator, EvaluableItem, SequenceIterable, TailCallReturner, InstructionInfoProvider
Direct Known Subclasses:
DocumentInstr, ElementCreator

public abstract class ParentNodeConstructor
extends Instruction

An abstract class to act as a common parent for instructions that create element nodes and document nodes.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
ParentNodeConstructor()
          Create a document or element node constructor instruction
 
Method Summary
 PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
          Add a representation of this expression to a PathMap.
 int computeCardinality()
          Get the cardinality of the sequence returned by evaluating this instruction
 boolean createsNewNodes()
          Determine whether this instruction creates new nodes.
 String getBaseURI()
          Get the static base URI of the instruction
 int getCardinality()
          Determine the static cardinality of the expression.
 Expression getContentExpression()
          Get the expression that constructs the content of the element
 SchemaType getSchemaType()
          Get the schema type chosen for validation; null if not defined
 int getValidationMode()
          Get the validation mode for this instruction
 boolean isLazyConstruction()
          Establish whether lazy construction is to be used
 boolean isNamespaceSensitive()
          Determine whether the schema type is namespace sensitive.
 Iterator iterateSubExpressions()
          Get the immediate sub-expressions of this expression.
 Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
          Perform optimisation of an expression and its subexpressions.
 boolean replaceSubExpression(Expression original, Expression replacement)
          Replace one subexpression by a replacement subexpression
 void setBaseURI(String uri)
          Set the static base URI of the instruction
 void setContentExpression(Expression content)
          Set the expression that constructs the content of the element
 void setLazyConstruction(boolean lazy)
          Indicate that lazy construction should (or should not) be used.
 void setSchemaType(SchemaType type)
          Set the schema type to be used for validation
 void setValidationMode(int mode)
          Set the validation mode for the new document or element node
 Expression simplify(ExpressionVisitor visitor)
          Simplify an expression.
 Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
          Perform type checking of an expression and its subexpressions.
 
Methods inherited from class net.sf.saxon.instruct.Instruction
computeSpecialProperties, evaluateAsString, evaluateItem, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, iterate, process, processLeavingTail, promote
 
Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, copy, display, doPromotion, effectiveBooleanValue, explain, explain, findParentOf, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterateEvents, markTailFunctionCalls, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface javax.xml.transform.SourceLocator
getColumnNumber, getLineNumber, getPublicId, getSystemId
 

Constructor Detail

ParentNodeConstructor

public ParentNodeConstructor()
Create a document or element node constructor instruction

Method Detail

setBaseURI

public void setBaseURI(String uri)
Set the static base URI of the instruction

Parameters:
uri - the static base URI

getBaseURI

public String getBaseURI()
Get the static base URI of the instruction

Returns:
the static base URI

setLazyConstruction

public void setLazyConstruction(boolean lazy)
Indicate that lazy construction should (or should not) be used. Note that this request will be ignored if validation is required

Parameters:
lazy - set to true if lazy construction should be used

isLazyConstruction

public final boolean isLazyConstruction()
Establish whether lazy construction is to be used

Returns:
true if lazy construction is to be used

setSchemaType

public void setSchemaType(SchemaType type)
Set the schema type to be used for validation

Parameters:
type - the type to be used for validation. (For a document constructor, this is the required type of the document element)

getSchemaType

public SchemaType getSchemaType()
Get the schema type chosen for validation; null if not defined

Returns:
the type to be used for validation. (For a document constructor, this is the required type of the document element)

isNamespaceSensitive

public boolean isNamespaceSensitive()
Determine whether the schema type is namespace sensitive. The result is undefined if schemaType is null.

Returns:
true if the schema type is namespace sensitive

setValidationMode

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

Parameters:
mode - the validation mode, for example Validation.STRICT

getValidationMode

public int getValidationMode()
Get the validation mode for this instruction

Returns:
the validation mode, for example Validation.STRICT or Validation.PRESERVE

setContentExpression

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

Parameters:
content - the content expression

getContentExpression

public Expression getContentExpression()
Get the expression that constructs the content of the element

Returns:
the content expression

computeCardinality

public int computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction

Overrides:
computeCardinality in class Instruction
Returns:
the static cardinality

simplify

public Expression simplify(ExpressionVisitor visitor)
                    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 class Instruction
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
Description copied from class: Expression
Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

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 may not be accurately known if they have not been explicitly declared.

If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:
typeCheck in class Expression
Parameters:
visitor - an expression visitor
contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
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)

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
                    throws XPathException
Description copied from class: Expression
Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:
optimize in class Expression
Parameters:
visitor - an expression visitor
contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
Returns:
the original expression, rewritten if appropriate to optimize execution
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

iterateSubExpressions

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

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

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace one subexpression by a replacement subexpression

Overrides:
replaceSubExpression in class Expression
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

createsNewNodes

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

Overrides:
createsNewNodes in class Instruction
Returns:
true if the instruction creates new nodes (or if it can't be proved that it doesn't)

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).

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Overrides:
addToPathMap in class Expression
Parameters:
pathMap - the PathMap to which the expression should be added
pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
Returns:
the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.


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