net.sf.saxon.query
Class XQueryExpression

java.lang.Object
  net.sf.saxon.query.XQueryExpression

All Implemented Interfaces:

SourceLocator, Container

public class XQueryExpression
extends Object
implements Container

XQueryExpression represents a compiled query. This object is immutable and thread-safe, the same compiled query may be executed many times in series or in parallel. The object can be created only by using the compileQuery method of the QueryProcessor class.

Various methods are provided for evaluating the query, with different options for delivery of the results.

Method Summary

List	evaluate(DynamicQueryContext env) Execute a the compiled Query, returning the results as a List.
Object	evaluateSingle(DynamicQueryContext env) Execute the compiled Query, returning the first item in the result.
void	explain(Configuration config, PrintStream out) Diagnostic method: display a representation of the compiled query on the selected output stream.
int	getColumnNumber() Return the character position where the current document event ends.
Controller	getController() Deprecated. since 8.5.1 - use newController()
Executable	getExecutable() Get the Executable (representing a complete stylesheet or query) of which this Container forms part
Expression	getExpression() Get the expression wrapped in this XQueryExpression object
int[]	getExternalVariableNames() Get a list containing the fingerprints of the names of the external variables in the query
int	getHostLanguage() Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
int	getLineNumber() Return the line number where the current document event ends.
LocationProvider	getLocationProvider() Get the LocationProvider allowing location identifiers to be resolved.
String	getPublicId() Return the public identifier for the current document event.
SlotManager	getStackFrameMap() Get the stack frame map used for the outermost level of this query
StaticQueryContext	getStaticContext() Get the static context in which this expression was compiled.
String	getSystemId() Return the system identifier for the current document event.
SequenceIterator	iterator(DynamicQueryContext env) Get an iterator over the results of the expression.
Controller	newController() Get a controller that can be used to execute functions in this compiled query.
void	pull(DynamicQueryContext dynamicEnv, Result destination, Properties outputProperties) Run the query in pull mode.
boolean	replaceSubExpression(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression.
void	run(DynamicQueryContext env, Result result, Properties outputProperties) Run the query, sending the results directly to a JAXP Result object.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getExpression

public Expression getExpression()

Get the expression wrapped in this XQueryExpression object

Returns:

the underlying expression

getStackFrameMap

public SlotManager getStackFrameMap()

Get the stack frame map used for the outermost level of this query

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)

Replace one subexpression by a replacement subexpression. For internal use only

Specified by:

replaceSubExpression in interface Container

Parameters:

original - the original subexpression

replacement - the replacement subexpression

Returns:

true if the original subexpression is found

getStaticContext

public StaticQueryContext getStaticContext()

Get the static context in which this expression was compiled. Note, this will be an internal copy of the original user-created StaticQueryContext object. The user-created object is not modified by Saxon, whereas the copy includes additional information found in the query prolog.

Returns:

the internal copy of the StaticQueryContext. This is available for inspection, but should not be modified or reused by the application.

getExternalVariableNames

public int[] getExternalVariableNames()

Get a list containing the fingerprints of the names of the external variables in the query

Returns:

an array of integers, being the integer fingerprints of external variables

evaluate

public List evaluate(DynamicQueryContext env)
              throws XPathException

Execute a the compiled Query, returning the results as a List.

Parameters:

env - Provides the dynamic query evaluation context

Returns:

The results of the expression, as a List. The List represents the sequence of items returned by the expression. Each item in the list will either be an object representing a node, or an object representing an atomic value. For the types of Java object that may be returned, see the description of the evaluate method of class XPathProcessor

Throws:

XPathException

evaluateSingle

public Object evaluateSingle(DynamicQueryContext env)
                      throws XPathException

Execute the compiled Query, returning the first item in the result. This is useful where it is known that the expression will only return a singleton value (for example, a single node, or a boolean).

Parameters:

env - Provides the dynamic query evaluation context

Returns:

The first item in the sequence returned by the expression. If the expression returns an empty sequence, this method returns null. Otherwise, it returns the first item in the result sequence, represented as a Java object using the same mapping as for the evaluate method

Throws:

XPathException

iterator

public SequenceIterator iterator(DynamicQueryContext env)
                          throws XPathException

Get an iterator over the results of the expression. This returns results without any conversion of the returned items to "native" Java classes. The iterator will deliver a sequence of Item objects, each item being either a NodeInfo (representing a node) or an AtomicValue (representing an atomic value).

To get the results of the query in the form of an XML document in which each item is wrapped by an element indicating its type, use:

QueryResult.wrap(iterator(env))

To serialize the results to a file, use the QueryResult.serialize() method.

Parameters:

env - Provides the dynamic query evaluation context

Returns:

an iterator over the results of the query. The class SequenceIterator is modeled on the standard Java Iterator class, but has extra functionality and can throw exceptions when errors occur.

Throws:

XPathException - if a dynamic error occurs in evaluating the query. Some dynamic errors will not be reported by this method, but will only be reported when the individual items of the result are accessed using the returned iterator.

run

public void run(DynamicQueryContext env,
                Result result,
                Properties outputProperties)
         throws XPathException

Run the query, sending the results directly to a JAXP Result object. This way of executing the query is most efficient in the case of queries that produce a single document (or parentless element) as their output, because it avoids constructing the result tree in memory: instead, it is piped straight to the serializer.

Parameters:

env - the dynamic query context

result - the destination for the results of the query. The query is effectively wrapped in a document{} constructor, so that the items in the result are concatenated to form a single document; this is then written to the requested Result destination, which may be (for example) a DOMResult, a SAXResult, or a StreamResult

outputProperties - Supplies serialization properties, in JAXP format, if the result is to be serialized. This parameter can be defaulted to null.

Throws:

XPathException - if the query fails.

pull

public void pull(DynamicQueryContext dynamicEnv,
                 Result destination,
                 Properties outputProperties)
          throws XPathException

Run the query in pull mode.

For maximum effect this method should be used when lazyConstructionMode has been set in the Configuration.

Throws:

XPathException

See Also:

Configuration.setLazyConstructionMode(boolean)

newController

public Controller newController()

Get a controller that can be used to execute functions in this compiled query. Functions in the query module can be found using StaticQueryContext.getUserDefinedFunction(java.lang.String, java.lang.String, int). They can then be called directly from the Java application using UserFunction.call(net.sf.saxon.om.ValueRepresentation[], net.sf.saxon.expr.XPathContextMajor) The same Controller can be used for a series of function calls.

getController

public Controller getController()

Deprecated. since 8.5.1 - use newController()

Deprecated synonym for newController()

explain

public void explain(Configuration config,
                    PrintStream out)

Diagnostic method: display a representation of the compiled query on the selected output stream.

getExecutable

public Executable getExecutable()

Get the Executable (representing a complete stylesheet or query) of which this Container forms part

Specified by:

getExecutable in interface Container

getLocationProvider

public LocationProvider getLocationProvider()

Get the LocationProvider allowing location identifiers to be resolved.

Specified by:

getLocationProvider in interface Container

getPublicId

public String getPublicId()

Return the public identifier for the current document event.

The return value is the public identifier of the document entity or of the external parsed entity in which the markup that triggered the event appears.

Specified by:

getPublicId in interface SourceLocator

Returns:

A string containing the public identifier, or null if none is available.

See Also:

getSystemId()

getSystemId

public String getSystemId()

Return the system identifier for the current document event.

The return value is the system identifier of the document entity or of the external parsed entity in which the markup that triggered the event appears.

If the system identifier is a URL, the parser must resolve it fully before passing it to the application.

Specified by:

getSystemId in interface SourceLocator

Returns:

A string containing the system identifier, or null if none is available.

See Also:

getPublicId()

getLineNumber

public int getLineNumber()

Return the line number where the current document event ends.

Warning: The return value from the method is intended only as an approximation for the sake of error reporting; it is not intended to provide sufficient information to edit the character content of the original XML document.

The return value is an approximation of the line number in the document entity or external parsed entity where the markup that triggered the event appears.

Specified by:

getLineNumber in interface SourceLocator

Returns:

The line number, or -1 if none is available.

See Also:

getColumnNumber()

getColumnNumber

public int getColumnNumber()

Return the character position where the current document event ends.

Warning: The return value from the method is intended only as an approximation for the sake of error reporting; it is not intended to provide sufficient information to edit the character content of the original XML document.

The return value is an approximation of the column number in the document entity or external parsed entity where the markup that triggered the event appears.

Specified by:

getColumnNumber in interface SourceLocator

Returns:

The column number, or -1 if none is available.

See Also:

getLineNumber()

getHostLanguage

public int getHostLanguage()

Get the host language (XSLT, XQuery, XPath) used to implement the code in this container

Specified by:

getHostLanguage in interface Container

Returns:

typically Configuration.XSLT or Configuration.XQUERY