Package net.sf.saxon.expr
Class FirstItemExpression
- java.lang.Object
-
- net.sf.saxon.expr.Expression
-
- net.sf.saxon.expr.UnaryExpression
-
- net.sf.saxon.expr.SingleItemFilter
-
- net.sf.saxon.expr.FirstItemExpression
-
- All Implemented Interfaces:
ExportAgent,Locatable,IdentityComparable,Traceable
public final class FirstItemExpression extends SingleItemFilter
A FirstItemExpression returns the first item in the sequence returned by a given base expression
-
-
Field Summary
-
Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD
-
-
Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description Expressioncopy(RebindingMap rebindings)Copy an expression.ItemevaluateItem(XPathContext context)Evaluate the expressionjava.lang.StringgetExpressionName()Get a name identifying the kind of expression, in terms meaningful to a user.intgetImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().java.lang.StringgetStreamerName()Get the (partial) name of a class that supports streaming of this kind of expressionstatic ExpressionmakeFirstItemExpression(Expression base)Static factory methodPatterntoPattern(Configuration config)Convert this expression to an equivalent XSLT patternjava.lang.StringtoShortString()Produce a short string identifying the expression for use in error messages-
Methods inherited from class net.sf.saxon.expr.SingleItemFilter
computeCardinality, getOperandRole, optimize
-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeHashCode, computeSpecialProperties, displayOperator, emitExtraAttributes, equals, export, getBaseExpression, getItemType, getOperand, operands, setBaseExpression, toString, typeCheck
-
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, typeCheckChildren, typeError, unordered, verifyParentPointers
-
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
-
Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
-
-
-
-
Method Detail
-
makeFirstItemExpression
public static Expression makeFirstItemExpression(Expression base)
Static factory method- Parameters:
base- A sequence expression denoting sequence whose first item is to be returned- Returns:
- the FirstItemExpression, or an equivalent
-
copy
public Expression copy(RebindingMap rebindings)
Copy an expression. This makes a deep copy.- Specified by:
copyin classExpression- Parameters:
rebindings-- Returns:
- the copy of the original expression
-
toPattern
public Pattern toPattern(Configuration config) throws XPathException
Convert this expression to an equivalent XSLT pattern- Overrides:
toPatternin classExpression- Parameters:
config- the Saxon configuration- Returns:
- the equivalent pattern
- Throws:
XPathException- if conversion is not possible
-
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 provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.- Specified by:
getImplementationMethodin classExpression- Returns:
- the implementation method, for example
Expression.ITERATE_METHODorExpression.EVALUATE_METHODorExpression.PROCESS_METHOD
-
evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate the expression- Overrides:
evaluateItemin classExpression- 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
-
getExpressionName
public java.lang.String getExpressionName()
Description copied from class:ExpressionGet a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionNamein classExpression- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the expression.
-
toShortString
public java.lang.String toShortString()
Description copied from class:ExpressionProduce a short string identifying the expression for use in error messages- Overrides:
toShortStringin classUnaryExpression- Returns:
- a short string, sufficient to identify the expression
-
getStreamerName
public java.lang.String getStreamerName()
Get the (partial) name of a class that supports streaming of this kind of expression- Overrides:
getStreamerNamein classExpression- Returns:
- the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class
-
-