Package net.sf.saxon.query

Class XQueryExpression

  • All Implemented Interfaces:
    javax.xml.transform.SourceLocator, ExpressionOwner, Locatable, Location, Traceable, TraceableComponent, org.xml.sax.Locator
    Direct Known Subclasses:
    XQueryExpressionEE
    public class XQueryExpression
extends java.lang.Object
implements Location, ExpressionOwner, TraceableComponent
    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 is intended to 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.

    • Constructor Detail

      • XQueryExpression

        public XQueryExpression​(Expression exp,
                        QueryModule mainModule,
                        boolean streaming)
                 throws XPathException
        The constructor should only be called using the compileQuery() methods of StaticQueryContext
        Parameters:
        exp - an expression to be wrapped as an XQueryExpression
        mainModule - the static context of the main module
        streaming - true if streamed execution is requested
        Throws:
        XPathException - if an error occurs

    • Method Detail

      • getExpression

        public Expression getExpression()
        Get the expression wrapped in this XQueryExpression object
        Returns:
        the underlying expression

      • getBody

        public Expression getBody()
        Description copied from interface: TraceableComponent
        Get the expression at the root of the expression tree used to evaluate this construct
        Specified by:
        getBody in interface TraceableComponent
        Returns:
        the root expression

      • setBody

        public void setBody​(Expression expression)
        Description copied from interface: TraceableComponent
        Set the expression to be used to evaluate this construct
        Specified by:
        setBody in interface TraceableComponent
        Parameters:
        expression - the evaluation expression

      • getObjectName

        public StructuredQName getObjectName()
        Get a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc. This is used only where the name is known statically.
        Specified by:
        getObjectName in interface Traceable
        Returns:
        the QName of the object declared or manipulated by this instruction or expression

      • getTracingTag

        public java.lang.String getTracingTag()
        Description copied from interface: TraceableComponent
        Get a string to identify the type of component
        Specified by:
        getTracingTag in interface TraceableComponent
        Returns:
        an identifying string

      • getLocation

        public Location getLocation()
        Description copied from interface: Locatable
        Get the location of the construct
        Specified by:
        getLocation in interface Locatable
        Returns:
        the location. If no location information is available, the method should return Loc.NONE rather than returning null. However, callers would be well advised to check for the result being null.

      • getPackageData

        public PackageData getPackageData()
        Get data about the unit of compilation (XQuery module, XSLT package) to which this container belongs

      • getConfiguration

        public Configuration getConfiguration()
        Get the Configuration to which this Container belongs
        Returns:
        the Configuration

      • 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

      • 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.

      • getStackFrameMap

        public SlotManager getStackFrameMap()
        Get the stack frame map used for the outermost level of this query
        Returns:
        the stack frame map

      • explainPathMap

        public void explainPathMap()
        Output the path map of the query for diagnostics

      • getMainModule

        public QueryModule getMainModule()
        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.

      • getExternalVariableNames

        public StructuredQName[] 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

      • evaluate

        public java.util.List<java.lang.Object> evaluate​(DynamicQueryContext env)
                                          throws XPathException
        Execute a the compiled Query, returning the results as a List of objects obtained by converting the items in the query result to the nearest appropriate Java type
        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 XPathEvaluator.evaluate(java.lang.String, java.lang.Object, javax.xml.namespace.QName) method of class XPathProcessor
        Throws:
        XPathException - if a dynamic error occurs during query evaluation

      • evaluateSingle

        public java.lang.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(net.sf.saxon.query.DynamicQueryContext) method
        Throws:
        XPathException - if evaluation fails with a dynamic error

      • 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,
                javax.xml.transform.Result result,
                java.util.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.

        If the output method specified in the outputProperties, or declared in the query itself, is one of XML, HTML, XHTML, or TEXT, or if it is defaulted to XML, then the query is implicitly wrapped in a document node constructor to implement the "sequence normalization" phase described in the Serialization specification. If the output method is JSON or ADAPTIVE then this phase is skipped and the items produced by the query are piped straight into 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.

      • closeStreamIfNecessary

        protected void closeStreamIfNecessary​(javax.xml.transform.stream.StreamResult result,
                                      boolean mustClose)
                               throws XPathException
        Throws:
        XPathException

      • runStreamed

        public void runStreamed​(DynamicQueryContext dynamicEnv,
                        javax.xml.transform.Source source,
                        javax.xml.transform.Result result,
                        java.util.Properties outputProperties)
                 throws XPathException
        Run the query in streaming mode, assuming it has been compiled for streaming. This requires Saxon-EE.
        Parameters:
        dynamicEnv - the dynamic execution context
        source - the input document, as a SAXSource or StreamSource
        result - the destination for the query results
        outputProperties - serialization options for the query result
        Throws:
        XPathException - if streamed evaluation of the query fails

      • validateOutputProperties

        protected java.util.Properties validateOutputProperties​(Controller controller,
                                                        java.util.Properties outputProperties)
        Validate the serialization properties requested; any problems result in warnings being output
        Parameters:
        controller - The query controller
        outputProperties - the requested serialization properties (may be null)
        Returns:
        the properties after validation and normalization

      • runUpdate

        public java.util.Set<MutableNodeInfo> runUpdate​(DynamicQueryContext dynamicEnv)
                                         throws XPathException
        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

      • runUpdate

        public void runUpdate​(DynamicQueryContext dynamicEnv,
                      UpdateAgent agent)
               throws XPathException
        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
        agent - a callback class that is called to process each document updated by the query
        Throws:
        XPathException - if evaluation of the update query fails, or it this is not an updating query

      • explain

        public void explain​(ExpressionPresenter out)
             throws XPathException
        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
        Throws:
        XPathException

      • getExecutable

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

      • setAllowDocumentProjection

        public void setAllowDocumentProjection​(boolean allowed)
        Indicate that document projection is or is not allowed
        Parameters:
        allowed - true if projection is allowed

      • isDocumentProjectionAllowed

        public boolean isDocumentProjectionAllowed()
        Ask whether document projection is allowed
        Returns:
        true if document projection is allowed

      • getPublicId

        public java.lang.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 Location
        Specified by:
        getPublicId in interface org.xml.sax.Locator
        Specified by:
        getPublicId in interface javax.xml.transform.SourceLocator
        Returns:
        A string containing the public identifier, or null if none is available.
        See Also:
        getSystemId()

      • getSystemId

        public java.lang.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 Location
        Specified by:
        getSystemId in interface org.xml.sax.Locator
        Specified by:
        getSystemId in interface javax.xml.transform.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 Location
        Specified by:
        getLineNumber in interface org.xml.sax.Locator
        Specified by:
        getLineNumber in interface javax.xml.transform.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 Location
        Specified by:
        getColumnNumber in interface org.xml.sax.Locator
        Specified by:
        getColumnNumber in interface javax.xml.transform.SourceLocator
        Returns:
        The column number, or -1 if none is available.
        See Also:
        getLineNumber()

      • saveLocation

        public Location saveLocation()
        Get an immutable copy of this Location object. By default Location objects may be mutable, so they should not be saved for later use. The result of this operation holds the same location information, but in an immutable form.
        Specified by:
        saveLocation in interface Location
        Returns:
        an immutable copy (which may be the original object, if it is already immutable)

      • getHostLanguage

        public HostLanguage getHostLanguage()
        Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
        Returns:
        HostLanguage.XQUERY