net.sf.saxon.s9api

Class XQueryEvaluator

java.lang.Object

net.sf.saxon.s9api.XQueryEvaluator

All Implemented Interfaces:

Iterable<XdmItem>, Destination

public class XQueryEvaluator
extends Object
implements Iterable<XdmItem>, Destination

An XQueryEvaluator represents a compiled and loaded query ready for execution. The XQueryEvaluator holds details of the dynamic evaluation context for the query.

An XQueryEvaluator must not be used concurrently in multiple threads. It is safe, however, to reuse the object within a single thread to run the same query several times. Running the query does not change the context that has been established.

An XQueryEvaluator is always constructed by running the Load method of an XQueryExecutable.

An XQueryEvaluator is itself a Iterable. This makes it possible to evaluate the results in a for-each expression.

An XQueryEvaluator is itself a Destination. This means it is possible to use one XQueryEvaluator as the destination to receive the results of another transformation, this providing a simple way for transformations to be chained into a pipeline. When the query is executed this way, setDestination(Destination) must be called to provide a destination for the result of this query. Note however that a when the input to a query is supplied in this way, it will always be built as a tree in memory, rather than the transformation being streamed.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	XQueryEvaluator(Processor processor, XQueryExpression expression) Protected constructor

Method Summary

Methods

Modifier and Type	Method and Description
XdmValue	callFunction(QName function, XdmValue[] arguments) Call a global user-defined function in the compiled query.
void	close() Close this destination, allowing resources to be released.
XdmValue	evaluate() Perform the query, returning the results as an XdmValue.
XdmItem	evaluateSingle() Evaluate the XQuery expression, returning the result as an XdmItem (that is, a single node or atomic value).
XdmItem	getContextItem() Get the initial context item for the query, if one has been set
ErrorListener	getErrorListener() Get the error listener.
XdmValue	getExternalVariable(QName name) Get the value that has been set for an external variable
Receiver	getReceiver(Configuration config) Return a Receiver which can be used to supply the principal source document for the transformation.
ValidationMode	getSchemaValidationMode() Get the schema validation mode for the transformation.
PrintStream	getTraceFunctionDestination() Get the destination for output from the fn:trace() function.
TraceListener	getTraceListener() Get the registered TraceListener, if any
DynamicQueryContext	getUnderlyingQueryContext() Get the underlying dynamic context object.
Iterator<XdmNode>	getUpdatedDocuments() After executing an updating query using the run() method, iterate over the root nodes of the documents updated by the query.
URIResolver	getURIResolver() Get the URI resolver.
Iterator<XdmItem>	iterator() Evaluate the query, and return an iterator over its results.
void	run() Perform the query.
void	run(Destination destination) Perform the query, sending the results to a specified destination.
void	setContextItem(XdmItem item) Set the initial context item for the query
void	setDestination(Destination destination) Set the destination to be used for the query results
void	setErrorListener(ErrorListener listener) Set the error listener.
void	setExternalVariable(QName name, XdmValue value) Set the value of external variable defined in the query
void	setSchemaValidationMode(ValidationMode mode) Set the schema validation mode for the transformation.
void	setSource(Source source) Set the source document for the query.
void	setTraceFunctionDestination(PrintStream stream) Set the destination for output from the fn:trace() function.
void	setTraceListener(TraceListener listener) Set a TraceListener which will receive messages relating to the evaluation of all expressions.
void	setURIResolver(URIResolver resolver) Set an object that will be used to resolve URIs used in fn:doc() and related functions.

Methods inherited from class java.lang.Object

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

Constructor Detail

XQueryEvaluator

protected XQueryEvaluator(Processor processor,
               XQueryExpression expression)

Protected constructor

Parameters:

processor - the Saxon processor

expression - the XQuery expression

Method Detail

setSchemaValidationMode

public void setSchemaValidationMode(ValidationMode mode)

Set the schema validation mode for the transformation. This indicates how source documents loaded specifically for this transformation will be handled. This applies to the principal source document if supplied as a SAXSource or StreamSource, and to all documents loaded during the transformation using the doc(), document(), or collection() functions.

Parameters:

mode - the validation mode. Passing null causes no change to the existing value. Passing Validation.DEFAULT resets to the initial value, which determines the validation requirements from the Saxon Configuration.

getSchemaValidationMode

public ValidationMode getSchemaValidationMode()

Get the schema validation mode for the transformation. This indicates how source documents loaded specifically for this transformation will be handled. This applies to the principal source document if supplied as a SAXSource or StreamSource, and to all documents loaded during the transformation using the doc(), document(), or collection() functions.

Returns:

the validation mode.

setSource

public void setSource(Source source)
               throws SaxonApiException

Set the source document for the query.

If the source is an instance of NodeInfo, the supplied node is used directly as the context node of the query.

If the source is an instance of DOMSource, the DOM node identified by the DOMSource is wrapped as a Saxon node, and this is then used as the context item

In all other cases a new Saxon tree is built, by calling DocumentBuilder.build(javax.xml.transform.Source), and the document node of this tree is then used as the context item for the query.

Parameters:

source - the source document to act as the initial context item for the query.

Throws:

SaxonApiException

setContextItem

public void setContextItem(XdmItem item)

Set the initial context item for the query

Parameters:

item - the initial context item, or null if there is to be no initial context item

getContextItem

public XdmItem getContextItem()

Get the initial context item for the query, if one has been set

Returns:

the initial context item, or null if none has been set. This will not necessarily be the same object as was supplied, but it will be an XdmItem object that represents the same underlying node or atomic value.

setExternalVariable

public void setExternalVariable(QName name,
                       XdmValue value)

Set the value of external variable defined in the query

Parameters:

name - the name of the external variable, as a QName

value - the value of the external variable, or null to clear a previously set value

getExternalVariable

public XdmValue getExternalVariable(QName name)

Get the value that has been set for an external variable

Parameters:

name - the name of the external variable whose value is required

Returns:

the value that has been set for the external variable, or null if no value has been set

setURIResolver

public void setURIResolver(URIResolver resolver)

Set an object that will be used to resolve URIs used in fn:doc() and related functions.

Parameters:

resolver - An object that implements the URIResolver interface, or null.

getURIResolver

public URIResolver getURIResolver()

Get the URI resolver.

Returns:

the user-supplied URI resolver if there is one, or the system-defined one otherwise

setErrorListener

public void setErrorListener(ErrorListener listener)

Set the error listener. The error listener receives reports of all run-time errors and can decide how to report them.

Parameters:

listener - the ErrorListener to be used

getErrorListener

public ErrorListener getErrorListener()

Get the error listener.

Returns:

the ErrorListener in use

setTraceListener

public void setTraceListener(TraceListener listener)

Set a TraceListener which will receive messages relating to the evaluation of all expressions. This option has no effect unless the query was compiled to enable tracing.

Parameters:

listener - the TraceListener to use

getTraceListener

public TraceListener getTraceListener()

Get the registered TraceListener, if any

Returns:

listener the TraceListener in use, or null if none has been set

setTraceFunctionDestination

public void setTraceFunctionDestination(PrintStream stream)

Set the destination for output from the fn:trace() function. By default, the destination is System.err. If a TraceListener is in use, this is ignored, and the trace() output is sent to the TraceListener.

Parameters:

stream - the PrintStream to which trace output will be sent. If set to null, trace output is suppressed entirely. It is the caller's responsibility to close the stream after use.

Since:

9.1

getTraceFunctionDestination

public PrintStream getTraceFunctionDestination()

Get the destination for output from the fn:trace() function.

Returns:

the PrintStream to which trace output will be sent. If no explicitly destination has been set, returns System.err. If the destination has been set to null to suppress trace output, returns null.

Since:

9.1

setDestination

public void setDestination(Destination destination)

Set the destination to be used for the query results

Parameters:

destination - the destination to which the results of the query will be sent

run

public void run()
         throws SaxonApiException

Perform the query.

• In the case of a non-updating query, the results are sent to the registered Destination.
• In the case of an updating query, all updated documents will be available after query execution as the result of the getUpdatedDocuments() method.

Throws:

SaxonApiException - if any dynamic error occurs during the query

IllegalStateException - if this is a non-updating query and no Destination has been supplied for the query results

run

public void run(Destination destination)
         throws SaxonApiException

Perform the query, sending the results to a specified destination.

This method must not be used with an updating query.

This method is designed for use with a query that produces a single node (typically a document node or element node) as its result. If the query produces multiple nodes, the effect depends on the kind of destination. For example, if the result is an XdmDestination, only the last of the nodes will be accessible.

Parameters:

destination - The destination where the result document will be sent

Throws:

SaxonApiException - if any dynamic error occurs during the query

IllegalStateException - if this is an updating query

evaluate

public XdmValue evaluate()
                  throws SaxonApiException

Perform the query, returning the results as an XdmValue. This method must not be used with an updating query

Returns:

an XdmValue representing the results of the query

Throws:

SaxonApiException - if the query fails with a dynamic error

IllegalStateException - if this is an updating query

evaluateSingle

public XdmItem evaluateSingle()
                       throws SaxonApiException

Evaluate the XQuery expression, returning the result as an XdmItem (that is, a single node or atomic value).

Returns:

an XdmItem representing the result of the query, or null if the query returns an empty sequence. If the expression returns a sequence of more than one item, any items after the first are ignored.

Throws:

SaxonApiException - if a dynamic error occurs during the query evaluation.

Since:

9.2

iterator

public Iterator<XdmItem> iterator()
                           throws SaxonApiUncheckedException

Evaluate the query, and return an iterator over its results.

This method must not be used with an updating query.

Specified by:

iterator in interface Iterable<XdmItem>

Throws:

SaxonApiUncheckedException - if a dynamic error is detected while constructing the iterator. It is also possible for an SaxonApiUncheckedException to be thrown by the hasNext() method of the returned iterator if a dynamic error occurs while evaluating the result sequence.

IllegalStateException - if this is an updating query

getReceiver

public Receiver getReceiver(Configuration config)
                     throws SaxonApiException

Return a Receiver which can be used to supply the principal source document for the transformation. This method is intended primarily for internal use, though it can also be called by a user application that wishes to feed events into the query engine.

Saxon calls this method to obtain a Receiver, to which it then sends a sequence of events representing the content of an XML document. This method is provided so that XQueryEvaluator implements Destination, allowing one transformation to receive the results of another in a pipeline.

Note that when an XQueryEvaluator is used as a Destination, the initial context node set on that XQueryEvaluator (using setSource(javax.xml.transform.Source)) is ignored.

Specified by:

getReceiver in interface Destination

Parameters:

config - The Saxon configuration. This is supplied so that the destination can use information from the configuration (for example, a reference to the name pool) to construct or configure the returned Receiver.

Returns:

the Receiver to which events are to be sent.

Throws:

SaxonApiException - if the Receiver cannot be created

IllegalStateException - if no Destination has been supplied

close

public void close()
           throws SaxonApiException

Close this destination, allowing resources to be released. Used when this XQueryEvaluator is acting as the destination of another transformation or query. Saxon calls this method when it has finished writing to the destination.

Specified by:

close in interface Destination

Throws:

SaxonApiException - if any failure occurs

getUpdatedDocuments

public Iterator<XdmNode> getUpdatedDocuments()

After executing an updating query using the run() method, iterate over the root nodes of the documents updated by the query.

The results remain available until a new query is executed. This method returns the results of the most recently executed query. It does not consume the results.

Returns:

an iterator over the root nodes of documents (or other trees) that were updated by the query

Since:

9.1

callFunction

public XdmValue callFunction(QName function,
                    XdmValue[] arguments)
                      throws SaxonApiException

Call a global user-defined function in the compiled query.

If this is called more than once (to evaluate the same function repeatedly with different arguments, or to evaluate different functions) then the sequence of evaluations uses the same values of global variables including external variables (query parameters); the effect of any changes made to query parameters between calls is undefined.

Parameters:

function - The name of the function to be called

arguments - The values of the arguments to be supplied to the function. These must be of the correct type as defined in the function signature (there is no automatic conversion to the required type).

Throws:

SaxonApiException - if no function has been defined with the given name and arity; or if any of the arguments does not match its required type according to the function signature; or if a dynamic error occurs in evaluating the function.

Since:

9.3

getUnderlyingQueryContext

public DynamicQueryContext getUnderlyingQueryContext()

Get the underlying dynamic context object. This provides an escape hatch to the underlying implementation classes, which contain methods that may change from one release to another.

Returns:

the underlying object representing the dynamic context for query execution