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Java client API for Franz AllegroGraph
/******************************************************************************
** Copyright (c) 2008-2016 Franz Inc.
** All rights reserved. This program and the accompanying materials
** are made available under the terms of the Eclipse Public License v1.0
** which accompanies this distribution, and is available at
** http://www.eclipse.org/legal/epl-v10.html
******************************************************************************/
package com.franz.agraph.http.handler;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.NoSuchElementException;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import org.apache.commons.httpclient.HttpMethod;
import org.openrdf.model.Value;
import org.openrdf.query.BindingSet;
import org.openrdf.query.QueryEvaluationException;
import org.openrdf.query.TupleQueryResult;
import org.openrdf.query.impl.MapBindingSet;
import org.openrdf.query.resultio.TupleQueryResultFormat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.franz.agraph.http.AGHttpRepoClient;
import com.franz.agraph.http.exception.AGHttpException;
import com.franz.agraph.repository.AGValueFactory;
import com.franz.util.Closer;
/**
* Similar to {@link org.openrdf.query.resultio.sparqlxml.SPARQLResultsXMLParser}
* but uses {@link XMLStreamReader} instead of SAXParser so the results
* streaming in the http response can be processed in a
* {@link TupleQueryResult} pulling from the stream.
*
* @since v4.3
*/
public class AGTQRStreamer extends AGResponseHandler {
private static final XMLInputFactory xmlInputFactory = XMLInputFactory.newInstance();
final Logger log = LoggerFactory.getLogger(this.getClass());
private final AGValueFactory vf;
private XMLStreamReader xml;
private HttpMethod method;
public AGTQRStreamer(TupleQueryResultFormat format, AGValueFactory vf) {
super(format.getDefaultMIMEType());
this.vf = vf;
}
@Override
public String getRequestMIMEType() {
return TupleQueryResultFormat.SPARQL.getDefaultMIMEType();
}
/**
* False because the Result will release the HTTP resources.
* For most responses, AGHTTPClient releases resources after
* calling {@link #handleResponse(HttpMethod)},
* but here the work is pulled later from the {@link Result}.
*/
@Override
public boolean releaseConnection() {
return false;
}
@Override
public void handleResponse(HttpMethod method) throws IOException, AGHttpException {
this.method = method;
try {
xml = xmlInputFactory.createXMLStreamReader(AGResponseHandler.getInputStream(method));
} catch (XMLStreamException e) {
throw new AGHttpException(e);
}
}
public TupleQueryResult getResult() {
return new Result();
}
class Result implements TupleQueryResult {
private List bindingNames;
private MapBindingSet next = null;
@Override
public List getBindingNames() {
if (bindingNames == null) {
try {
while (xml.hasNext()) {
switch (xml.next()) {
case XMLStreamConstants.START_ELEMENT:
if ("head".equals(xml.getLocalName())) {
bindingNames = new ArrayList();
}
else if ("variable".equals(xml.getLocalName())) {
for (int i = 0; i < xml.getAttributeCount(); i++) {
if ("name".equals(xml.getAttributeLocalName(i))) {
bindingNames.add(xml.getAttributeValue(i));
}
}
}
else if ("sparql".equals(xml.getLocalName())) {
// continue
} else {
throw new RuntimeException("Unexpected tag: " + xml.getLocalName());
//return null;
}
break;
case XMLStreamConstants.END_ELEMENT:
if ("head".equals(xml.getLocalName())) {
return bindingNames;
}
break;
}
}
} catch (XMLStreamException e) {
throw new RuntimeException(e);
}
}
return bindingNames;
}
@Override
public boolean hasNext() throws QueryEvaluationException {
if (next == null) {
if (closed) {
return false;
}
getBindingNames(); // must be done first
try {
String bindingName = null;
while (xml.hasNext()) {
final int event = xml.next();
if (xml.isStartElement()) {
String name = xml.getLocalName();
if ("result".equals(name)) {
next = new MapBindingSet(bindingNames.size());
}
else if ("results".equals(xml.getLocalName())) {
// continue
}
else if ("binding".equals(name)) {
for (int i = 0; i < xml.getAttributeCount(); i++) {
if ("name".equals(xml.getAttributeLocalName(i))) {
bindingName = xml.getAttributeValue(i);
}
}
}
else if ("literal".equals(name)) {
String lang = null;
String datatype = null;
for (int i = 0; i < xml.getAttributeCount(); i++) {
if ("lang".equals(xml.getAttributeLocalName(i))
&& "http://www.w3.org/XML/1998/namespace".equals(xml.getAttributeNamespace(i))) {
lang = xml.getAttributeValue(i);
}
else if ("datatype".equals(xml.getAttributeLocalName(i))) {
datatype = xml.getAttributeValue(i);
}
}
String text = xml.getElementText();
Value value = null;
if (datatype != null) {
try {
value = vf.createLiteral(text, vf.createURI(datatype));
} catch (IllegalArgumentException e) {
// Illegal datatype URI
throw new QueryEvaluationException(e.getMessage(), e);
}
}
else if (lang != null) {
value = vf.createLiteral(text, lang);
}
else {
value = vf.createLiteral(text);
}
next.addBinding(bindingName, value);
}
else if ("uri".equals(name)) {
next.addBinding(bindingName, AGHttpRepoClient.getApplicationResource(vf.createURI(xml.getElementText()),vf));
}
else if ("bnode".equals(name)) {
next.addBinding(bindingName, vf.createBNode(xml.getElementText()));
} else {
log.warn("unknown elem: " + name + " attrs=" + xml.getAttributeCount());
}
}
else if (xml.isEndElement()) {
if ("result".equals(xml.getLocalName())) {
return next != null;
}
else if ("results".equals(xml.getLocalName())) {
// in normal use, closed will be called here
close();
return false;
}
else if ("sparql".equals(xml.getLocalName())) {
close();
return false;
}
else if (!"binding".equals(xml.getLocalName())) {
log.warn("unknown elem end: " + xml.getLocalName());
}
} else if (event == XMLStreamConstants.END_DOCUMENT) {
close();
return false;
}
}
} catch (XMLStreamException e) {
throw new QueryEvaluationException(e);
}
}
return next != null;
}
@Override
public BindingSet next() throws QueryEvaluationException {
if (hasNext()) {
BindingSet curr = next;
next = null;
return curr;
} else if (closed) {
throw new RuntimeException("closed");
} else {
throw new NoSuchElementException();
}
}
private boolean closed = false;
@Override
public void close() throws QueryEvaluationException {
if ( ! closed) {
closed = true;
try {
Closer.Close(xml);
Closer.Close(method.getResponseBodyAsStream());
method.releaseConnection();
} catch (Exception e) {
log.warn("I/O error closing resources", e);
}
}
}
@Override
public void remove() throws QueryEvaluationException {
throw new UnsupportedOperationException();
}
}
}
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