Class XQueryExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,Container
Various methods are provided for evaluating the query, with different options for delivery of the results.
- See Also:
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Constructor Summary
ConstructorsModifierConstructorDescriptionprotected
XQueryExpression
(Expression exp, Executable exec, QueryModule mainModule, Configuration config) The constructor is protected, to ensure that instances can only be created using the compileQuery() methods of StaticQueryContext -
Method Summary
Modifier and TypeMethodDescriptionExecute a the compiled Query, returning the results as a List.Execute the compiled Query, returning the first item in the result.void
Diagnostic method: display a representation of the compiled query on the selected output stream.int
Return the character position where the current document event ends.Deprecated.since 8.5.1 - use newController()Get the Executable (representing a complete stylesheet or query) of which this Container forms partGet the expression wrapped in this XQueryExpression objectGet a list containing the names of the external variables in the query.int
Get the host language (XSLT, XQuery, XPath) used to implement the code in this containerint
Return the line number where the current document event ends.Get the LocationProvider allowing location identifiers to be resolved.Get the path map for the query expressionReturn the public identifier for the current document event.Get the stack frame map used for the outermost level of this queryGet the static context in which this expression was compiled.Return the system identifier for the current document event.boolean
Ask whether document projection is allowedboolean
Ask whether this is an update queryiterateEvents
(Controller controller, DynamicQueryContext dynamicEnv) Run the query returning the results as an EventIteratorGet an iterator over the results of the expression.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.void
pullOLD
(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.runUpdate
(DynamicQueryContext dynamicEnv) Run an updating queryvoid
runUpdate
(DynamicQueryContext dynamicEnv, UpdateAgent agent) Run an updating query, writing back eligible updated node to persistent storage.void
setAllowDocumentProjection
(boolean allowed) Indicate that document projection is or is not allowedboolean
Ask whether this query uses the context item
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Constructor Details
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XQueryExpression
protected XQueryExpression(Expression exp, Executable exec, QueryModule mainModule, Configuration config) throws XPathException The constructor is protected, to ensure that instances can only be created using the compileQuery() methods of StaticQueryContext- Parameters:
exp
- an expression to be wrapped as an XQueryExpressionexec
- the executablemainModule
- the static context of the main moduleconfig
- the configuration- Throws:
XPathException
- if an error occurs
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Method Details
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getExpression
Get the expression wrapped in this XQueryExpression object- Returns:
- the underlying expression
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usesContextItem
public boolean usesContextItem()Ask whether this query uses the context item- Returns:
- true if the context item is referenced either in the query body or in the initializer of any global variable
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isUpdateQuery
public boolean isUpdateQuery()Ask whether this is an update query- Returns:
- true if the body of the query is an updating expression (as defined by the XQuery Update specification). Note that a query can use Update syntax (notably the copy-modify syntax) without being an updating expression.
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getStackFrameMap
Get the stack frame map used for the outermost level of this query- Returns:
- the stack frame map
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replaceSubExpression
Replace one subexpression by a replacement subexpression. For internal use only- Specified by:
replaceSubExpression
in interfaceContainer
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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getStaticContext
Get the static context in which this expression was compiled. This is essentially an internal copy of the original user-created StaticQueryContext object, augmented with information obtained from the query prolog of the main query module, and with information about functions and variables imported from other library modules. The user-created StaticQueryContext object is not modified by Saxon, whereas the QueryModule object includes additional information found in the query prolog.- Returns:
- the QueryModule object representing the static context of the main module of the query. This is available for inspection, but must not be modified or reused by the application.
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getExternalVariableNames
Get a list containing the names of the external variables in the query.Changed in Saxon 9.0 to return an array of StructuredQName objects rather than integer fingerprints.
- Returns:
- an array of StructuredQName objects, representing the names of external variables defined in the query
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evaluate
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
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evaluateSingle
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
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iterator
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.
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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 contextresult
- 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 StreamResultoutputProperties
- 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.
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pullOLD
public void pullOLD(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.
Note: this method usually has very similar performance to the
run(DynamicQueryContext,javax.xml.transform.Result,java.util.Properties)
method (which does the same thing), but sometimes it is significantly slower. Therefore, the run() method is preferred.- Parameters:
dynamicEnv
- the dynamic context for query evaluationdestination
- the destination of the query resultsoutputProperties
- the serialization parameters- Throws:
XPathException
- See Also:
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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.
Note: this method usually has very similar performance to the
run(DynamicQueryContext,javax.xml.transform.Result,java.util.Properties)
method (which does the same thing), but sometimes it is significantly slower. Therefore, the run() method is preferred.- Parameters:
dynamicEnv
- the dynamic context for query evaluationdestination
- the destination of the query resultsoutputProperties
- the serialization parameters- Throws:
XPathException
- See Also:
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iterateEvents
public EventIterator iterateEvents(Controller controller, DynamicQueryContext dynamicEnv) throws XPathException Run the query returning the results as an EventIterator- Parameters:
controller
- The Controller used to run the querydynamicEnv
- the XQuery dynamic context for evaluating the query- Returns:
- an EventIterator representing the results of the query as a sequence of events
- Throws:
XPathException
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runUpdate
Run an updating query- Parameters:
dynamicEnv
- the dynamic context for query execution- Returns:
- a set of nodes representing the roots of trees that have been modified as a result
of executing the update. Note that this method will never modify persistent data on disk; it returns
the root nodes of the affected documents (which will often be document nodes whose document-uri can
be ascertained), and it is the caller's responsibility to decide what to do with them.
On completion of this method it is generally unsafe to rely on the contents or relationships of NodeInfo objects that were obtained before the updating query was run. Such objects may or may not reflect the results of the update operations. This is especially true in the case of nodes that are part of a subtree that has been deleted (detached from its parent). Instead, the new updated tree should be accessed by navigation from the root nodes returned by this method.
- Throws:
XPathException
- if evaluation of the update query fails, or it this is not an updating query
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runUpdate
Run an updating query, writing back eligible updated node to persistent storage.A node is eligible to be written back to disk if it is present in the document pool, which generally means that it was originally read using the doc() or collection() function.
On completion of this method it is generally unsafe to rely on the contents or relationships of NodeInfo objects that were obtained before the updating query was run. Such objects may or may not reflect the results of the update operations. This is especially true in the case of nodes that are part of a subtree that has been deleted (detached from its parent). Instead, the new updated tree should be accessed by navigation from the root nodes returned by this method.
If one or more eligible updated nodes cannot be written back to disk, perhaps because the URI identifies a non-updatable location, then an exception is thrown. In this case it is undefined
- Parameters:
dynamicEnv
- the dynamic context for query execution- Throws:
XPathException
- if evaluation of the update query fails, or it this is not an updating query
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newController
Get a controller that can be used to execute functions in this compiled query. Functions in the query module can be found usingQueryModule.getUserDefinedFunction(java.lang.String, java.lang.String, int)
. They can then be called directly from the Java application usingUserFunction.call(net.sf.saxon.om.ValueRepresentation[], net.sf.saxon.expr.XPathContextMajor)
The same Controller can be used for a series of function calls. Note that the Controller should only be used in a single thread.- Returns:
- a newly constructed Controller
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getController
Deprecated.since 8.5.1 - use newController()Deprecated synonym fornewController()
- Returns:
- a newly constructed Controller
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explain
Diagnostic method: display a representation of the compiled query on the selected output stream.- Parameters:
out
- an ExpressionPresenter to which the XML representation of the compiled query will be sent
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getExecutable
Get the Executable (representing a complete stylesheet or query) of which this Container forms part- Specified by:
getExecutable
in interfaceContainer
- Returns:
- the executable
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getPathMap
Get the path map for the query expression- Returns:
- the path map (which is constructed if this has not already been done)
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getLocationProvider
Get the LocationProvider allowing location identifiers to be resolved.- Specified by:
getLocationProvider
in interfaceContainer
- Returns:
- the location provider
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setAllowDocumentProjection
public void setAllowDocumentProjection(boolean allowed) Indicate that document projection is or is not allowed- Parameters:
allowed
- true if projection is allowed
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isDocumentProjectionAllowed
public boolean isDocumentProjectionAllowed()Ask whether document projection is allowed- Returns:
- true if document projection is allowed
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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 interfaceSourceLocator
- Returns:
- A string containing the public identifier, or null if none is available.
- See Also:
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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 interfaceSourceLocator
- Returns:
- A string containing the system identifier, or null if none is available.
- See Also:
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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 interfaceSourceLocator
- Returns:
- The line number, or -1 if none is available.
- See Also:
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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 interfaceSourceLocator
- Returns:
- The column number, or -1 if none is available.
- See Also:
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getHostLanguage
public int getHostLanguage()Get the host language (XSLT, XQuery, XPath) used to implement the code in this container- Specified by:
getHostLanguage
in interfaceContainer
- Returns:
- typically
Configuration.XSLT
orConfiguration.XQUERY
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