Class XQueryExpression

java.lang.Object
net.sf.saxon.query.XQueryExpression
All Implemented Interfaces:
Serializable, 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.

See Also:
  • Constructor Details

    • 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 XQueryExpression
      exec - the executable
      mainModule - the static context of the main module
      config - the configuration
      Throws:
      XPathException - if an error occurs
  • Method Details

    • getExpression

      public Expression getExpression()
      Get the expression wrapped in this XQueryExpression object
      Returns:
      the underlying expression
    • 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
    • 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 QueryModule 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.
    • 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 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.
    • 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 evaluation
      destination - the destination of the query results
      outputProperties - the serialization parameters
      Throws:
      XPathException
      See Also:
    • 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 evaluation
      destination - the destination of the query results
      outputProperties - the serialization parameters
      Throws:
      XPathException
      See Also:
    • 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 query
      dynamicEnv - the XQuery dynamic context for evaluating the query
      Returns:
      an EventIterator representing the results of the query as a sequence of events
      Throws:
      XPathException
    • runUpdate

      public Set 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
      Throws:
      XPathException - if evaluation of the update query fails, or it this is not an updating query
    • 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 QueryModule.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. Note that the Controller should only be used in a single thread.
      Returns:
      a newly constructed Controller
    • getController

      public Controller getController()
      Deprecated.
      since 8.5.1 - use newController()
      Deprecated synonym for newController()
      Returns:
      a newly constructed Controller
    • explain

      public void explain(ExpressionPresenter out)
      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
    • 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
      Returns:
      the executable
    • getPathMap

      public PathMap getPathMap()
      Get the path map for the query expression
      Returns:
      the path map (which is constructed if this has not already been done)
    • getLocationProvider

      public LocationProvider getLocationProvider()
      Get the LocationProvider allowing location identifiers to be resolved.
      Specified by:
      getLocationProvider in interface Container
      Returns:
      the location provider
    • 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 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

      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:
    • 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

      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:
    • 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