Class ForEachGroup
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.instruct.Instruction
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- net.sf.saxon.instruct.ForEachGroup
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,ContextMappingFunction
,EvaluableItem
,SequenceIterable
,TailCallReturner
,SortKeyEvaluator
,InstructionInfo
,org.xml.sax.Locator
public class ForEachGroup extends Instruction implements ContextMappingFunction, SortKeyEvaluator
Handler for xsl:for-each-group elements in stylesheet. This is a new instruction defined in XSLT 2.0- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description static int
GROUP_ADJACENT
static int
GROUP_BY
static int
GROUP_ENDING
static int
GROUP_STARTING
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Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description ForEachGroup(Expression select, Expression action, byte algorithm, Expression key, StringCollator collator, Expression collationNameExpression, java.lang.String baseURI, SortKeyDefinition[] sortKeys)
Create a for-each-group instruction
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description PathMap.PathMapNodeSet
addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap.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
computeDependencies()
Compute the dependencies of an expression, as the union of the dependencies of its subexpressions.Expression
copy()
Copy an expression.boolean
createsNewNodes()
Determine whether this instruction creates new nodes.Item
evaluateSortKey(int n, XPathContext c)
Callback for evaluating the sort keysvoid
explain(ExpressionPresenter out)
Diagnostic print of expression structure.Expression
getActionExpression()
Get the action expression (the content of the for-each-group)Expression
getGroupingKey()
Get the grouping key expression expression (the group-by or group-adjacent expression, or a PatternSponsor containing the group-starting-with or group-ending-with expression)int
getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposesItemType
getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instructionboolean
hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedlySequenceIterator
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence.java.util.Iterator
iterateSubExpressions()
Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)SequenceIterator
map(XPathContext context)
Map one item to a sequence.Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.TailCall
processLeavingTail(XPathContext context)
ProcessLeavingTail: called to do the real work of this instruction.protected void
promoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionExpression
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
assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getConstructType, getImplementationMethod, getSourceLocator, isXSLT, process, promote
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Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
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Field Detail
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GROUP_BY
public static final int GROUP_BY
- See Also:
- Constant Field Values
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GROUP_ADJACENT
public static final int GROUP_ADJACENT
- See Also:
- Constant Field Values
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GROUP_STARTING
public static final int GROUP_STARTING
- See Also:
- Constant Field Values
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GROUP_ENDING
public static final int GROUP_ENDING
- See Also:
- Constant Field Values
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Constructor Detail
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ForEachGroup
public ForEachGroup(Expression select, Expression action, byte algorithm, Expression key, StringCollator collator, Expression collationNameExpression, java.lang.String baseURI, SortKeyDefinition[] sortKeys)
Create a for-each-group instruction- Parameters:
select
- the select expression (selects the population to be grouped)action
- the body of the for-each-group (applied to each group in turn)algorithm
- one of group-by, group-adjacent, group-starting-with, group-ending-withkey
- expression to evaluate the grouping keycollator
- user for comparing stringscollationNameExpression
- expression that yields the name of the collation to be usedbaseURI
- static base URI of the expressionsortKeys
- list of xsl:sort keys for sorting the groups
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Method Detail
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getInstructionNameCode
public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes- Overrides:
getInstructionNameCode
in classInstruction
- Returns:
- the name of the instruction
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getActionExpression
public Expression getActionExpression()
Get the action expression (the content of the for-each-group)- Returns:
- the body of the xsl:for-each-group instruction
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getGroupingKey
public Expression getGroupingKey()
Get the grouping key expression expression (the group-by or group-adjacent expression, or a PatternSponsor containing the group-starting-with or group-ending-with expression)- Returns:
- the expression used to calculate grouping keys
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).- Specified by:
simplify
in classInstruction
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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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 classExpression
- Parameters:
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 toType.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)
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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 classExpression
- Parameters:
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 toType.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)
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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction- Overrides:
getItemType
in classInstruction
- Parameters:
th
- the type hierarchy cache- Returns:
- the static item type of the instruction
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computeDependencies
public int computeDependencies()
Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. (This is overridden for path expressions and filter expressions, where the dependencies of a subexpression are not all propogated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.- Overrides:
computeDependencies
in classExpression
- Returns:
- the depencies, as a bit-mask
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createsNewNodes
public final boolean createsNewNodes()
Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).- Overrides:
createsNewNodes
in classInstruction
- Returns:
- true if the instruction creates new nodes (or if it can't be proved that it doesn't)
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promoteInst
protected void promoteInst(PromotionOffer offer) throws XPathException
Handle promotion offers, that is, non-local tree rewrites.- Overrides:
promoteInst
in classInstruction
- Parameters:
offer
- The type of rewrite being offered- Throws:
XPathException
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iterateSubExpressions
public java.util.Iterator iterateSubExpressions()
Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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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 classExpression
- Parameters:
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
-- Returns:
- the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter 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.
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hasLoopingSubexpression
public boolean hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly- Overrides:
hasLoopingSubexpression
in classExpression
- Parameters:
child
- the immediate subexpression- Returns:
- true if the child expression is evaluated repeatedly
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Overrides:
replaceSubExpression
in classExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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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 classExpression
- Parameters:
parentType
- the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this typeenv
- the static contextwhole
- if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content- Throws:
XPathException
- if the value delivered by this expression cannot be part of the content model of the given type
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processLeavingTail
public TailCall processLeavingTail(XPathContext context) throws XPathException
Description copied from class:Instruction
ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.- Specified by:
processLeavingTail
in interfaceTailCallReturner
- Specified by:
processLeavingTail
in classInstruction
- Parameters:
context
- The dynamic context of the transformation, giving access to the current node, the current variables, etc.- Returns:
- null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
- Throws:
XPathException
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
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 relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence. In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.- Specified by:
iterate
in interfaceSequenceIterable
- Overrides:
iterate
in classInstruction
- 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
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map
public SequenceIterator map(XPathContext context) throws XPathException
Map one item to a sequence.- Specified by:
map
in interfaceContextMappingFunction
- Parameters:
context
- The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.- Returns:
- either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.
- Throws:
XPathException
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evaluateSortKey
public Item evaluateSortKey(int n, XPathContext c) throws XPathException
Callback for evaluating the sort keys- Specified by:
evaluateSortKey
in interfaceSortKeyEvaluator
- Throws:
XPathException
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explain
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
explain
in classExpression
- Parameters:
out
- the expression presenter used to display the structure
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