An abstract class to act as a common parent for instructions that create element nodes
and document nodes.
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.
- addToPathMap in interface Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
- the PathMapNodeSet to which the paths embodied in this expression should be added
- 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.
checkContentSequence
protected abstract void checkContentSequence(StaticContext env)
throws XPathException
Check that the child instructions don't violate any obvious constraints for this kind of node
computeCardinality
public int computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction
- computeCardinality in interface Instruction
createsNewNodes
public final boolean createsNewNodes()
Determine whether this instruction creates new nodes.
This implementation returns true.
- createsNewNodes in interface Instruction
getBaseURI
public String getBaseURI()
Get the static base URI of the instruction
getCardinality
public int getCardinality()
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.
- getCardinality in interface Expression
- 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).
getContentExpression
public Expression getContentExpression()
Get the expression that constructs the content of the element
getSchemaType
public SchemaType getSchemaType()
Get the schema type chosen for validation; null if not defined
- the type to be used for validation. (For a document constructor, this is the required
type of the document element)
getValidationMode
public int getValidationMode()
Get the validation mode for this instruction
isLazyConstruction
public final boolean isLazyConstruction()
Establish whether lazy construction is to be used
- true if lazy construction is to be used
isNamespaceSensitive
public boolean isNamespaceSensitive()
Determine whether the schema type is namespace sensitive. The result is undefined if schemaType is null.
- true if the schema type is namespace sensitive
iterateSubExpressions
public Iterator iterateSubExpressions()
Get the immediate sub-expressions of this expression.
- iterateSubExpressions in interface Expression
- an iterator containing the sub-expressions of this expression
optimize
public Expression optimize(ExpressionVisitor visitor,
ItemType contextItemType)
throws XPathException
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.
- optimize in interface Expression
visitor
- an expression visitorcontextItemType
- 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
- the original expression, rewritten if appropriate to optimize execution
XPathException
- if an error is discovered during this phase
(typically a type error)
replaceSubExpression
public boolean replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression
- replaceSubExpression in interface Expression
original
- the original subexpressionreplacement
- the replacement subexpression
- true if the original subexpression is found
setBaseURI
public void setBaseURI(String uri)
Set the static base URI of the instruction
uri
- the static base URI
setContentExpression
public void setContentExpression(Expression content)
Set the expression that constructs the content of the element
content
- the content expression
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
lazy
- set to true if lazy construction should be used
setSchemaType
public void setSchemaType(SchemaType type)
Set the schema type to be used for validation
type
- the type to be used for validation. (For a document constructor, this is the required
type of the document element)
setValidationMode
public void setValidationMode(int mode)
Set the validation mode for the new document or element node
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.
- simplify in interface Instruction
visitor
- an expression visitor
- the simplified expression
XPathException
- if an error is discovered during expression rewriting
typeCheck
public Expression typeCheck(ExpressionVisitor visitor,
ItemType contextItemType)
throws XPathException
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.
- typeCheck in interface Expression
visitor
- an expression visitorcontextItemType
- 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
- the original expression, rewritten to perform necessary run-time type checks,
and to perform other type-related optimizations
XPathException
- if an error is discovered during this phase
(typically a type error)