second API gives you more control over IPSI-XQ. You also provide a query
as String, but now you can choose to get the AST(abstract syntax tree), the result
type, or the query result as data model instance. See the following example:
import de.fraunhofer.ipsi.ipsixq.api.*;
...
XQIQueryHandler handler = XQIQueryHandlerFactory.getInstance().getQueryHandler(someQuery);
XQueryNode ast = handler.getXQuery();
String resultType = handler.getInferredType();
AnyType result = handler.getQueryResult();
IPSI-XQ release 1.3.3 introduces XQJ, the XQuery API for Java (see
JSR 225: XQuery API for JavaTM (XQJ)
for further information) as a third option for query execution and result processing.
XQJ is an attempt to standardize access to the XQuery datamodel for programs written in
the Java programming language. The current implementation of XQJ in IPSI-XQ should be
understood as a preview rather than state-of-the-art; the same applies to the API itself.
Its development status is marked as 'early draft review', and probably subject to future
changes.
IPSI-XQ currently supports most of the datamodel-exposing interfaces of XQJ, i.e.
retrieval and iteration of result sequences, extraction of nodes and atomic values
from sequences, binding external variables and rudimentary type querying facilities.
The following usage pattern illustrates the most important aspects of IPSI-XQ's XQJ support.
import javax.xml.xquery.*;
import de.fraunhofer.ipsi.ipsixq.api.impl.*;
//define the query
String query = "declare namespace my = \"http://www.example.com/my\";" +
"declare variable $my:elem external;" +
"declare variable $my:attr external;" +
"declare variable $my:float external;" +
"<elem>{ $my:attr, $my:elem }</elem>," +
"(1 to 10), $my:float";
//establish connection to IPSI-XQ engine
XQDatasource dataSource = new IPSIXQDataSource();
XQConnection connection = dataSource.getConnection();
//bind a DOM element node as an external variable in the dynamic context of the connection;
//this variable will be visible in all expressions created via that connection
Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
connection.bindNode(new QName("http://www.example.com/my", "elem", "my"), document.createElement("myElem"));
//create the expression used to carry out the query
XQExpression expression = connection.createExpression();
//bind additional external variables in the dynamic context of the expression
expression.bindNode(new QName("http://www.example.com/my", "attr", "my"), document.createAttribute("myAttr"));
expression.bindFloat(new QName("http://www.example.com/my", "float", "my"), (float) 20.375);
//execute query, process result sequence items according to their kind/type
XQResultSequence sequence = expression.executeQuery(query);
XQItem item = null;
Transformer transformer = TransformerFactory.newInstance().newTransformer();
while (sequence.next())
{
item = sequence.getItem();
if (item.getItemType().getBaseItemType() == XQItemType.XQITEMTYPE_DOCUMENT)
System.out.println("Document Node:");
else if (item.getItemType().getBaseItemType() == XQItemType.XQITEMTYPE_ELEMENT)
System.out.println("Element Node:");
else if (item.getItemType().getBaseItemType() == XQItemType.XQITEMTYPE_ATTRIBUTE)
System.out.println("Attribute Node:");
if (item.getItemType().getBaseItemType() == XQItemType.XQITEMTYPE_ATOMIC)
{
System.out.println("Atomic:");
XQItemType intType = connection.createItemType(XQItemType.XQITEMTYPE_ATOMIC, null, new QName("http://www.w3.org/2001/XMLSchema","integer","xs"), false);
if (item.instanceOf(intType))
{
System.out.println("xs:integer: " + item.getInt());
}
else
System.out.println("other: " + item.getString());
}
else
transformer.transform(new DOMSource(item.getNode()), new StreamResult(System.out));
}
More information about the various APIs can be found in the corresponding Javadoc documentation.
If you want to plug-in your own data sources into IPSI-XQ you should implement
your own DocumentManager(de.fraunhofer.ipsi.xquery.io.DocumentManager). A
DocumentManager handles the calls to the two input methods (doc(uri), collection(uri)).
If you implemented such a DocumentManager, you need to register it
with the Java system property "-DdocumentManager=aaa.bbb.ccc.CLASSNAME".
For this you normally also have to implement your own data model classes.
The interfaces and some more information about this can be found in the Javadoc
documentation.
Inorder to make the XQuery evaluator build your own data model classes, you
can implement and set your own DatamodelManager (de.fraunhofer.ipsi.xquery.datamodel.DatamodelManager)
with the Java system property "-DdatamodelManager=aaa.bbb.ccc.CLASSNAME".
For even more flexibility you can implement your own XQIQueryHandler
(de.fraunhofer.ipsi.ipsixq.api.XQIQueryHandler). This class handles the complete
query process and e.g. starts the individual processing steps. The instantiation
of an XQIQueryHandler is done in an XQIQueryHandlerFactory, which must be also
provided by you and registered with the Java system property
"-DxqueryFactory=aaa.bbb.ccc.CLASSNAME".
In the latest working drafts, XQuery allows to define external functions in a
query. This is supported by IPSI-XQ. See the following example for provinding
own external functions:
import de.fraunhofer.ipsi.xquery.functions.*;
import de.fraunhofer.ipsi.xquery.context.*;
import de.fraunhofer.ipsi.xquery.datamodel.*;
import de.fraunhofer.ipsi.xpathDatatypes.*;
public class MySqrt implements FunctionDefinition
{
public AnyType evaluate(List values, StaticContext stat, EvaluationContext eval)
throws FunctionException
{
AnyType val = (AnyType)value.get(0);
AtomicValue atomic = null;
if(val instanceof AtomicValue)
{
atomic = (AtomicValue)val;
}
else if(val instanceof Sequence)
{
atomic = (AtomicValue)((Sequence)val).getSequenceImpl().get(0);
}
XS_Double input = (XS_Double)atomic.value()
double result = Math.sqrt(input.doubleValue());
DatamodelManager manager = DatamodelManagerFactory.getInstance().getDatamodelManager();
return manager.newAtomicValue(new XS_Double(result));
}
}
...
ExternalFunctions functions = ExternalFunctions.getInstance();
XS_AnyURI uri = new XS_AnyURI("http://www.example.com/myfunctions");
XS_QName functionName = new XS_QName(uri, new XS_NCName("sqrt"));
functions.registerExternalFunction(functionName, new MySqrt());
...
(: An XQuery that calls my external function :)
declare namespace my = "http://www.example.com/myfunctions"
define function my:sqrt($val as xs:double) as xs:double external
my:sqrt(4)
