com.saxonica.deploy
Class CompiledQueryServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          com.saxonica.deploy.CompiledQueryServlet

All Implemented Interfaces:

Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public abstract class CompiledQueryServlet
extends javax.servlet.http.HttpServlet

This abstract class acts as a superclass for every query generated by the Saxon code generator in servlet mode. In this mode the generated code is thread-safe: it is possible to have a single instance of the class running in multiple threads concurrently.

It is possible to define a user-defined subclass of this class that specializes the behaviour of the init() and service() methods. When a query is compiled, the -superclass option on the command line determines the immediate superclass of the compiled code. Such a class will be needed, for example, if different queries are to share access to the same in-memory documents.

During servlet initialization, the init() method attempts to determine whether the servlet context includes an attribute named com.saxonica.servlet.applicationdata that is an instance of the interface SharedApplicationDataHandler. If this object exists, it is called on each servlet request, at which point it has the opportunity to configure the Controller for the query execution, for example by supplying parameter values, setting a URIResolver, or otherwise.

If no SharedApplicationDataHandler object is available, external variables for the query can be specified as query parameters in the request URL. The names of query parameters are taken as local names of no-namespace variables, and the values are treated as UntypedAtomic strings (which will be converted to the declared type of the variable if necessary). Any query parameters that do not correspond to declared external variables in the query will be ignored.

See Also:

Serialized Form

Field Summary

protected Configuration	config
protected Executable	exec
protected NamePool	namePool
protected SharedApplicationDataHandler	sharedData
protected TypeHierarchy	th

Constructor Summary

CompiledQueryServlet()

Method Summary

void	doGet(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse res) Run the query as a servlet
protected void	dynamicError(String message, String code, XPathContext context) Signal a dynamic error.
protected boolean	generalCompare(SequenceIterator iter1, SequenceIterator iter2, SimpleAtomicComparer comparer, XPathContext context) Helper method to implement a general comparison.
Configuration	getConfiguration() Get the Configuration.
protected NodeInfo	getContextNode(Item item) Helper method to get the context node, throwing appropriate exceptions if there isn't one.
Executable	getExecutable() Get the Executable.
protected abstract int	getNumberOfGlobalVariables() Get a StackFrameMap for the first local stackframe (that is, for the main query body).
void	init() Servlet initialization method
abstract void	initializeGlobals() Run the query-specific initialization code.
abstract void	process(XPathContext context) Run the query, sending the results to the current output destination.
protected void	runQuery(Controller controller, Result result, Properties outputProperties) Run the query, sending the results directly to a JAXP Result object.
void	setConfiguration(Configuration config) Supply the configuration in which the query will be executed.
protected abstract void	setExternalVariable(String clarkName, ValueRepresentation value, Controller controller)
protected void	typeError(String message, String code, XPathContext context) Signal a type error.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doOptions, doPost, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, init, log, log

Methods inherited from class java.lang.Object

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

Field Detail

config

protected Configuration config

exec

protected Executable exec

namePool

protected NamePool namePool

th

protected TypeHierarchy th

sharedData

protected SharedApplicationDataHandler sharedData

Constructor Detail

CompiledQueryServlet

public CompiledQueryServlet()

Method Detail

init

public void init()
          throws javax.servlet.ServletException

Servlet initialization method

Overrides:

init in class javax.servlet.GenericServlet

Throws:

javax.servlet.ServletException

initializeGlobals

public abstract void initializeGlobals()
                                throws XPathException

Run the query-specific initialization code. This method is present in each compiled query.

Throws:

XPathException

setConfiguration

public final void setConfiguration(Configuration config)

Supply the configuration in which the query will be executed. Note that this is not required to be the same as the configuration under which the query was compiled. However, any schemas that are present in the run-time configuration must be unchanged from the versions that were used at compile time. If no configuration is supplied then the query will run with a default configuration.

This method should be called during initialization by the init() method. If a user-defined subclass of CompiledQueryServlet is in use, the subclass may call this method directly. In the absence of such a class, the default implementation will call the SharedApplicationDataHandler to supply a Configuration; and in the absence of SharedApplicationDataHandler it will construct a Configuration specific to this servlet instance.

Parameters:

config - the Configuration to be used. If the query is schema-aware, this must be an instance of EnterpriseConfiguration

doGet

public void doGet(javax.servlet.http.HttpServletRequest req,
                  javax.servlet.http.HttpServletResponse res)
           throws javax.servlet.ServletException,
                  IOException

Run the query as a servlet

Overrides:

doGet in class javax.servlet.http.HttpServlet

Throws:

javax.servlet.ServletException

IOException

runQuery

protected void runQuery(Controller controller,
                        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:

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. Values supplied here take precedence over any values supplied in the query source using the saxon:output option declaration.

Throws:

XPathException - if the query fails.

getConfiguration

public final Configuration getConfiguration()

Get the Configuration. This method is provided for use by the compiled query code.

Returns:

the configuration in use.

getExecutable

public Executable getExecutable()

Get the Executable. This method is provided for use by the compiled query code.

Returns:

the Executable in use.

getNumberOfGlobalVariables

protected abstract int getNumberOfGlobalVariables()

Get a StackFrameMap for the first local stackframe (that is, for the main query body).

setExternalVariable

protected abstract void setExternalVariable(String clarkName,
                                            ValueRepresentation value,
                                            Controller controller)

process

public abstract void process(XPathContext context)
                      throws XPathException

Run the query, sending the results to the current output destination. This method is provided in each compiled query.

Throws:

XPathException

typeError

protected void typeError(String message,
                         String code,
                         XPathContext context)
                  throws XPathException

Signal a type error. This method is provided for use by the generated query code.

Parameters:

message -

code -

context -

Throws:

XPathException

dynamicError

protected void dynamicError(String message,
                            String code,
                            XPathContext context)
                     throws XPathException

Signal a dynamic error. This method is provided for use by the generated query code.

Parameters:

message -

code -

context -

Throws:

XPathException

getContextNode

protected NodeInfo getContextNode(Item item)
                           throws XPathException

Helper method to get the context node, throwing appropriate exceptions if there isn't one. This method is provided for use by the generated query code.

Throws:

XPathException

generalCompare

protected boolean generalCompare(SequenceIterator iter1,
                                 SequenceIterator iter2,
                                 SimpleAtomicComparer comparer,
                                 XPathContext context)
                          throws XPathException

Helper method to implement a general comparison. This method is provided for use by the generated query code.

Parameters:

iter1 - iterator over the first operand of the comparison

iter2 - iterator over the second operand of the comparison

comparer - object used to compare the two values

context - the XPath dynamic context

Returns:

true if the comparison is true, false if it is false.

Throws:

XPathException - if a dynamic error occurs